1. At the first stage, the geometric parameters of the jumper are determined.
For example, if the lintel is made of facing brick and is quite clearly visible, the facing brick of the wall will also not be additionally finished, then it makes sense to first determine at what radius (and arched lintels made of brick or natural stone are usually described by the equation of a circle) for cutting the stone the main wall will be minimal. If the arch is simple, without a pronounced lock, then the arch lifting boom can be taken as a multiple of the height of the masonry row. For example, when constructing brick walls with a height of 65 mm, the height of the masonry row will be approximately 77 mm or 0.077 m.
Note: For arches with a lifting boom equal to half the span length, i.e. representing half a circle, no special calculations of geometric parameters are required. For arched lintels, the central axis of which is described not by the equation of a circle, but by a parabola, ellipse or a combination of equations, the selection of geometric parameters will be more complex, but for our example it is enough for us to consider an arch whose axis is described by the equation of a circle.
Picture 1. Geometric parameters of the arched lintel.
Figure 1 shows an arched lintel over a span of L = 2.35 m, the arch boom is taken to be h = 4 0.077 = 0.308 m. But in order to design a lintel, you need to know not just the length of the span, but the length of the arc of the circle, in other words, the length arches at the bottom. Since bricks will be laid out along this circle, and in order not to have to adjust them to size, especially if it is planned to make a lot of such arched lintels, the length of the arch should be approximately a multiple of 0.07-0.075 m. The knowledge passed on to us by ancient Greek geometers allows for height and span length determine the length of the arch, but first you have to determine the angle A . Because:
h = (L/2)(tg( a/4)) , (278.1.1)
which follows from the geometry of a right triangle, then
tg( a/4) = 2h/L= 2·0.308/2.35 = 0.26213, (278.1.2)
A/4 = 14.688 o, hence A= 58.75 o.
Now we can determine the value of the circle radius:
R = h/(1 - cos( a/2)) = 0.308/(1 - 0.871) = 2.395 m, (278.1.3)
Note: In general, the derivation of this formula is quite simple, but for those who do not understand why this formula looks exactly like this, I will explain. In Figure 1, among other things, we see a triangle with a hypotenuse R and leg R-h(in this case the second leg is equal L/2, we are not interested), we also know the angle between the hypotenuse and the leg - a/2. Basic knowledge of geometry allows us to determine the meaning of this leg:
R - h = Rcos(a/2) (278.1.3.1)
Having carried out a number of simple transformations with this formula, we obtain formula (278.1.3). But just in case, I’ll give you the whole series:
R - h - R = Rcos(a/2) - R- subtract R from both sides of the equation (278.1.3.2)
- h = Rcos(a/2) - R (278.1.3.3)
- h(-1) = (-1)(R Rcos(a/2) - R)- multiply both sides of the equation by (-1) (278.1.3.4)
h = R - Rcos(a/2) (278.1.3.5)
h = R(1 - cos(a/2))- on the right side of the equation we take the common term out of brackets (278.1.3.6)
h/(1 - cos(a/2)) = R(1 - cos(a/2))/(1 - cos(a/2))- divide both sides of the equation by (1 - cos(a/2)) (278.1.3.7)
h/(1 - cosa/2) = R (278.1.3)
Why this can be done with equations is discussed separately.
And finally we can determine the length of the arc of a circle:
m = PRa/180 = 3.141 2.395 58.75/180 = 2.456 m, (278.1.4)
Since the arched lintel is planned to be symmetrical, an odd number of bricks must be used to construct it. For example, if we take the thickness of the mortar layer at the bottom point to be 5 mm, then the arch can be laid out of 2.456/0.07 = 35.08 bricks, or rather 35 bricks, and with a mortar thickness at the bottom point of 10 mm, then 2.456/0.075 = 32.74 bricks, and more precisely, from 33 bricks, while the thickness of the mortar layer at the lowest point should be about 2.456/33 - 0.065 = 0.0094 m or 9.4 mm. Of course, there is no need to achieve such accuracy when installing the jumper; it is enough to ensure that as the jumper is laid out, a large error does not occur.
I prefer the 35 brick option. With this option, the thickness of the mortar layer in the upper part of the lintel will be approximately 12.5 mm (since the radius for the top of the lintel is 2.395 + 0.25 = 2.645 m and the length of the circular arc will increase accordingly). When using 33 bricks, the thickness of the mortar layer in the upper part of the arched lintel will be about 17 mm, which in general is also within acceptable limits.
2. At this point, the calculation of the geometric parameters of the arched lintel can be completed and we can proceed to the strength calculation.
2.1. Determination of loads per 1 linear meter of lintel:
2.1.1 From the weight of the masonry:
q 1 = p x b x h, (278.2.1)
Where p in kg/m 3 - the density of the material from which the wall is laid, including cement-sand mortar and plaster, if any is planned. The density of cement-sand mortar on ordinary quartz sand is up to 2200 kg/m 3, which must be taken into account when working with hollow bricks, ceramic, gypsum blocks and lightweight concrete blocks, but in order not to waste time determining the percentage of the mortar in the masonry, you can simply multiply the density of the material used by 1.1 -1.2 or take the maximum of the following.
For reference:
- Density of solid brick 1600 - 1900 (depending on material)
- Density of hollow bricks 1000 - 1450 (depending on the nature of the voids)
- The density of blocks made of foam concrete, aerated concrete, cellular concrete is 300-1600 (more accurately, the density of cellular blocks can be determined by grade D)
- Density of gypsum blocks 900 -1200
For example:
- if the wall above the lintel is laid out of ordinary red brick using face hollow brick, then for reliability you can take the value p=1800-1900 kg/m3.
- For gypsum blocks p =1200
- For lightweight concrete blocks - depending on the density of the concrete. To determine this very density, you need to weigh 1 block (or try to approximately determine the weight of the block by simply lifting it), and then divide the weight by the height, width and thickness of the block. For example, if a block weighs 20 kg and has dimensions of 0.3x0.6x0.1 m, then the density of the block will be 20/ (0.3x0.6x0.1) = 1111 kg/m 3. In the same way, you can determine the density of the brick.
- In all other cases (especially if you do not know the density of the material and cannot determine its density) p =1900
b- wall thickness in meters, for example, for a brick wall of two bricks should be taken b = 0.51-0.55 m, for walls not finished with wet plaster b = 0.51 m, for walls finished with wet plaster only indoors b = 0.53 m, for walls finished with wet plaster both inside and outside b = 0.55 m, if the walls are insulated from the inside or covered with dry plaster, then the weight of the insulation and dry plaster should also be taken into account, but again, to simplify the calculations, you can take the thickness of the wall b = 0.53 m.
h- the height of the masonry above the lintel. And here several questions may arise: what to do if the height of the masonry above the lintel is 10 meters, or even more? Is it really necessary to take this entire masonry height into account? SNiP II-22-81 (1995) “Stone and reinforced masonry structures” in such cases recommends calculating the lintel for a load from the masonry height equal to 1/3 of the span length. This recommendation is based on the peculiarities of the transfer of internal stresses in various types of plates, which, from a theoretical point of view, is what a wall is. For greater reliability, I recommend calculating the load from the height of the masonry, equal to 1/2 the length of the opening. Among other things, such recommendations allow us to ignore the fact that the load from the masonry varies unevenly along the length of the lintel and, ideally, the structure should be designed taking these features into account. However, calculation with a margin allows you to avoid these additional calculation difficulties.
If there is another opening above the design opening, then the height brickwork in this case, it can be taken equal to the distance between the top of the lower opening and the bottom of the upper opening, again for reasons of reliability. If the width of the piers is significantly less than the length of the opening, then it makes sense to rely on the lintel to bear the load from the entire height of the overlying wall, even if it is 10 m or more, but in this case you need to check the strength of the masonry for tangential stresses, and in general make an arched lintel on the opening , if the width of the walls is less than 1/3 of the length of the opening, I would not recommend it. In most cases, it is enough to count on a load from the height of the masonry equal to 1/2 the length of the opening. In this case
For the opening L= 2.35 m for a brick wall 2 bricks thick load q 1 = 1900 x 0.53 x 0.5 x 2.35 = 1183.23 kg/m
2.1.2. From the own weight of the arched lintel:
The arched lintel we are designing has a rather complex geometric shape, however, taking into account the fact that we previously accepted the load from the overlying masonry with a good margin, it is enough to approximately calculate the load from its own weight:
q 2 = р x b x h x m/L , (278.2.2)
since we reduce the load from our own weight to the length of the opening.
For an arched lintel with a boom 0.308 m above the opening length L= 2.35 m q 2 = 1900 x 0.53 x 0.25 x 2.456/2.35 = 263.1 kg/m
2.1.3. From finishing materials walls
Walls can be finished with various materials: dry or wet plaster, ceramic tiles, natural or artificial stone, plastic or aluminum panels, etc. Loads from these and other finishing materials should be taken into account when calculating if these materials will be directly attached to the wall. If the walls are simply plastered on one or both sides, then this load has already been taken into account in paragraph 2.1.1. If it is not yet known what exactly the walls will be finished with, then you can multiply the load from the masonry (clause 2.1.1) by a correction factor of 1.2-1.3.
2.1.4. From the floor structure.
If the wall in which the arched lintel is made is load-bearing, then the load from beams or floor slabs should also be taken into account if the mark of the bottom of the floor is below the mark corresponding to 1/3 of the length of the opening. Simply put, if from the top of the lintel we are considering to the bottom of the floor is less than 2.35/3 = 0.78 m, then the load from the floor structure should be taken into account. And I recommend doing this even if the distance from the top of the lintel in question to the bottom of the ceiling is less than 2.35/2 = 1.175 m.
In addition to the weight of the floor structure, the live load must also be taken into account.
For reference, the design load per 1 m2 of floors, depending on the design, can be:
- Overlapping with wooden joists or metal beams - 400-600
- Overlapping on reinforced concrete beams - 500 - 700
- Flooring made of ready-made reinforced concrete slabs - 700-1000
- The ceiling is made of a monolithic reinforced concrete slab - the load is determined by calculation.
To determine the load from the floor structure, as well as everything that will be permanently or temporarily located on the floor, you need to know the length of the floor elements.
For an opening length L= 2.35 m for a load-bearing wall with hollow core slabs 6 m long load from the floor slabs taking into account the live load q 4 = 800 x 0.5 x 6 = 2400 kg/m
Thus, the linear design load on the jumper is:
q = q 1 + q 2 + q 3 + q 4
For the opening under consideration, the total design load is q = 1183.23 + 263.1 + 2400 = 3846.3 kg/m
What to do if not floor slabs, which give a uniformly distributed load, are used, but beams, which give a conditionally concentrated load, can be viewed separately.
2.2.1 Selecting a design scheme.
Here the first ambush awaits us. Because our arched lintel can be considered as an arch on two hinged supports with two horizontal connections. This means that such an arch is once statically indeterminate. Because there are four unknown reactions of the supports, and only 3 equations of static equilibrium can be compiled. This means that to calculate such a lintel it is necessary to know, among other things, the modulus of elasticity of the brickwork of the arch, as well as the moment of inertia of the cross sections. And if we consider the arch as rigidly clamped, then the degree of static indetermination will increase to 3. However, the designer’s task is not to complicate the problem condition, but to simplify it. If we consider our arch as three-jointed, i.e. with an additional hinge in the lock, this will make it possible to determine without any problems all the support reactions and then determine the maximum stresses in the cross sections of the arch. This assumption can be made on the following grounds:
For arches, the determining factor, as a rule, is not the value of the bending moment, but the longitudinal compressive force. This is the main difference between arches and straight beams. Moreover, it is possible to select a geometric shape of the arch such that the bending moment in all cross sections of the arch will be equal to 0.
Even if we were mistaken and a bending moment acts in the arch lock, then in the worst case this can lead to the formation of a plastic hinge due to exceeding the design resistance. A plastic hinge will not violate the geometric immutability of the arch, moreover, it does not interfere with the transfer of normal stresses and leads to a more uniform distribution of stresses along the height of the arch section, thus leveling the value of the bending moment, and is therefore completely acceptable.
Note: Today there is no single method for calculating arched double-hinged or rigidly clamped lintels; nevertheless, arched lintels made of stone have been erected since ancient times and still stand successfully. How the ancient builders of viaducts and bridges managed to comprehend the intricacies of calculating arched lintels is a mystery, but most likely the strength of the structures was achieved by using the most durable materials. Therefore, if during the calculation there are doubts about its correctness, then it is better to use the most durable bricks or masonry stones and mortar for reliability. In any case, the stronger the stones and mortar, the less will be the deformation of the arched lintel from the current loads.
2.2.2. Determination of design parameters.
Since the calculation will be carried out relative to the axis passing through the centers of gravity of the cross sections of the arch, the geometric parameters of the axis should first be more accurately determined:
Figure 2. Design diagram of the arched lintel.
The radius of the circle described by the axis of the arch will be greater by half the length of the brick and will be r= 2.395 + 0.125 = 2.52 m
The estimated span length will also increase slightly and will be l = L+ 0.25sin(a/2) = 2.35 + 0.1226 = 2.472 m
Then the arch arrow will be (according to formula (278.1.1)) f= (2.472/2)0.26213 = 0.324 m
2.3.1 Determination of vertical support reactions
Since the load on our symmetrical arch is uniformly distributed, then
V A = V B = ql/2 = 3846.3 2.472/2 = 4754 kgf (149.1)
2.3.2 Determination of horizontal support reactions
Since only a vertical load acts on the arch, the horizontal support reactions will be equal in value and oppositely directed, and to determine one of the horizontal reactions it is enough to create an equation of moments relative to the hinge we have additionally adopted - the arch lock:
∑М С = V A l/2 - ql 2 /8 - H A f = 0,
H A = (V A l/2 - ql 2 /8)/f = (4754 1.236 - 3846.3 2.472 2 /8)/0.324 = 9067.9 kgf.
Now is the time to determine the maximum internal stresses in the cross sections of the arch, to construct diagrams of transverse forces, bending moments and longitudinal forces for our arch, for which it would be good to use the computer that you are currently using for its intended purpose, namely for calculations, since it is necessary to solve a certain set of equations. Moreover, the more cross sections are considered, the more equations there will be in the end. However, understanding the fundamentals of strength of strength allows you to reduce the number of equations to be solved to a minimum. For example, for our arched lintel, it is enough to determine the values of transverse forces, bending moment and longitudinal forces for three characteristic sections - at the beginning of the arch, in the middle - where the lock is and at a point located in the middle between the beginning of the arch and the lock.
At point A:
Q = V A cos(a/2) + H A sin(a/2) = 4754 0.8714 + 9067.9 0.4905 = 8590.8 kgf
N = V A sin(a/2) + H A cos(a/2) = 4754 0.4905 + 9067.9 0.8714 = 10233.65 kgf
At point C(arch lock):
Q = V A - ql/2 = 0
M =0 (since we created the equation of moments with respect to this point in paragraph 2.3.2)
N = H A = 9067.9 kgf
At point D(midway between the beginning and the lock of the arch):
For this point, the coordinates along the x and y axes should be more accurately determined. Again, even basic knowledge of geometry allows us to do this quite easily; further details of the process of determining coordinates are not given, but for further calculations it is enough for us to know that the coordinates of point D along the axis x = 0.5776 m, along the axis y = 0.2337 m, Then
Q = V A cos(a/4) + H A sin(a/4) - qcos(a/4)x = 4754 0.9673 + 9067.9 0.2535 - 2221.45 0.9673 0.5776 = 5656.1 kgf
М =V A x - H A y - qx 2 /2 = 4754 0.5776 - 9067.9 0.2337 - 3846.3 0.5776 2 /2 = -14.8625 kgf m
N = V A sin(a/4) + H A cos(a/4) - qsin(a/4)x = 4754 0.2535 + 9067.9 0.9673 - 2221.45 0.2535 0.5776 = 9651.25 kgf
Note: in general, the angle of inclination of the tangent to the horizontal at point D will not be equal to α/4, but nevertheless it will be close to this value, which we accepted to simplify the calculations.
As we can see, the value of the bending moment that occurs in one of the cross sections of the arch (at point D) is quite small, and the maximum forces occur at the beginning and end of the arched lintel (at points A and B), it is for these sections that the strength needs to be checked .
2.4. Determination of maximum stresses.
And here a second ambush awaits us, because calculations according to the theory of strength of materials in its pure form can only be carried out for cross sections in which only one type of stress acts. In the cross section we are considering, both transverse force and compressive force act, which means tangential and normal stresses arise, and today there is no exact answer on how to make calculations in such cases. Let me remind you that today there are at least 5 theories of strength and the formulas proposed by these theories for such cases are somewhat different. But we will, as always, follow the path of the greatest margin and make calculations according to the third theory of strength, according to which:
σ pr =(σ 2 +4 T 2) 0.5 (278.4)
Where σ - normal voltage
σ = N/F = 10233.65/(0.51 0.25) = 80263.9 kg/m 2 or 8.026 kg/cm 2
Where F- cross-sectional area of our arched lintel
T= 1.5Q/F = 1.5 8590.8/(0.51 0.25) = 101068 kg/m 2 or 10.107 kg/cm 2
σ pr = (8.026 2 + 4 10.107 2) 0.5 = 21.75 kg/cm 2
2.5. Determining the required design resistance
Well, now everything is simple:
σ pr ≤ R (278.5)
where R is the design resistance of the brickwork
Now it is enough to select the ratio of the brand of brick and mortar according to Table 1.
Our conditions are satisfied by bricks or stones of grade M150 and higher, laid on mortar of grade M100 and higher
As already mentioned, the stronger the lintel, the less deformation there will be, which means the better the aesthetic appearance. That's the whole calculation.
If it was not possible to select brick and mortar due to too much load on the lintel, then the radius of the lintel should be reduced. The smaller the radius of the jumper, the smaller the value of the horizontal support reactions will be and the smaller the component of tangential stresses at the beginning of the jumper will be. In addition, reducing the radius of the lintel will lead to a decrease in the load acting from the weight of the masonry on the arched lintel and from the floor slabs. When the arch is about 1/3-1/2 the width of the opening, such loads will be minimal, which is explained by the peculiarities of stress redistribution in an appropriately loaded plate, which in this case is a brick wall. However, plate calculation is a separate big topic. Since the width of the piers is assumed to be much greater than the height of the cross section of the arch, no additional calculation of the support sections for strength is required.
And yet, if instead of an arched lintel you make a straight one, for example, from rolled metal, then in order to withstand the design load, at least 3 channels or I-beams No. 12 would be required. In this case, the calculated moment in the middle of the jumper would be about 2655 kgf m, i.e. almost 200 times more than what we obtained for the section at point D.
Note: Reduce the design compressive strength for masonry highest quality It’s not required, but I don’t know what kind of masonry you will have, so we’ll do the rest ourselves. But all the same, the seams between the bricks of the arch must be filled with very high quality mortar - this is the main condition for the strength and minimal deformation of the arch under load.
In multi-row masonry, versts are connected with backfill in bonded rows. Therefore, they are made only from whole bricks and must be laid in the first and last rows of laid out structures. Bonded rows of whole bricks are laid at the level of edges of walls and pillars, in protruding rows of masonry (cornices, corbels, etc.), under beams, purlins, floor slabs, balcony and cornice slabs, mauerlats, etc. Whole selected bricks are used also when constructing pillars and partitions with a width of 2"/2 bricks or less.
Laying lintels. Openings in the walls are blocked with lintels to maintain the masonry. Lintels of various designs, covering window, door and other openings, are not only a load-bearing element that absorbs vertical loads, but also an architectural part of buildings and structures.
Load-bearing lintels in addition to the mass of the masonry sections laid out above them, they take the load from the floors resting on these sections of the masonry.
In low-rise buildings, brick lintels can be installed - ordinary, wedge, beam and arched. Openings with a span of up to 2 m are covered with ordinary, wedge and beam lintels, and up to 4 m - with arched ones.
Ordinary jumpers They are an ordinary single-row masonry made of selected whole bricks, extended into the piers at a distance of at least 25 cm from the side slope of the opening. The height of the lintel masonry is not less than "/4 the width of the opening, but not less than 4 rows of bricks. Under the bottom row of bricks, steel reinforcement is placed in a layer of mortar at the rate of one rod with a cross-section of 20 mm 2 for each! /2 anchoring bricks, the ends of the reinforcing bars are bent and inserted into the masonry walls at least 25 cm.
Wedge, beam and arched lintels laid out on formwork of the appropriate shape. The formation of wedges is achieved by using a special wedge-shaped (pattern) or hewn brick with the same seam thickness or by using wedge-shaped radial seams that thicken up to 25 mm at the top and narrow down to 5 mm. Such jumpers are laid from the heels to the middle. The brick should fit tightly into the central locking row and tightly wedge the lintel.
4.9. Organization of the masons' workplace.
By doing stone works The productivity of masons is greatly influenced by the correct organization of the workplace. The organization of the workplace should eliminate unproductive movements of workers and ensure the highest labor productivity. Therefore, the workplace should be within the range of the crane, have a width of about 2.5 m and be divided into three zones: a working area 0.6...0.7 m wide between the wall and materials, in which masons move; a materials zone about 1 m wide for placing pallets with stone and boxes with mortar and a transportation zone of 0.8...0.9 m for moving materials and the passage of workers not directly involved with the masonry.
Number of pallets With stone and boxes with mortar and their alternation depends on the thickness of the wall or structure, the number of openings in a given area and the complexity of the architectural design.
Since the greatest height, and which is still rational for laying, is 1.2 m, then all stone buildings and structures are divided by height into tiers of the same size. Therefore, when the masonry reaches such a height, it is necessary to stop work" and install (or rearrange) the scaffolding. In order to coordinate the process of installing the scaffolding and ensure the constant employment of masons, the building or structure is divided in plan into occupations and plots. Occupations are sections of a building or structure under construction, into of which the labor intensity of the work is approximately the same. The occupation is allocated to a team of masons. Each occupation is divided into plots, which are sections of masonry allocated to a team of masons. The work is organized as follows: after finishing laying a tier in one area, the masons move to another area, and on the first they install or rearrange scaffolding or install floors.
The execution of work when laying walls is closely related to a number of related and auxiliary works. Thus, transport workers ensure a continuous supply of materials to workplaces. After finishing the masonry, carpenters install scaffolding to the height of the tier. Upon completion of the floor laying, the installers begin installing the floors, staircases, and partitions.
The work of teams of various specialties must be organized so that there is no downtime. This is achieved using the flow-grabbing method, when the building under construction is divided in plan into parts of equal labor intensity - grips, and in height - into tiers.
So, if the building is divided into two sections, then on one of them brickwork is carried out, and on the other at this time prefabricated reinforced concrete floors and stairs are installed or the scaffolding is rearranged (this can be done in the second shift). Procurement of part of the bricks at workplaces is possible in the third shift or in the second with the installation of scaffolding. The rest of the brick, as well as the mortar, is supplied continuously during the laying process.
When organizing work in a continuous manner, it is necessary that the laying of the walls of one floor on the first section is completed in the same time as required for the installation of floors and scaffolding on the second section. This makes it possible for masons and installers to change places after finishing their work on the grips: the masons move to the second grip for laying the walls of the next floor, and the installers move to the first for installing floors on the finished walls.
If you put the required number of masons on the block, the laying of one tier of walls can be completed in one shift. In this case (if the scaffolding is rearranged in the second shift), the laying of one floor on an occupation is completed in 3 days, and the laying of one floor on the entire building is completed in 6 days.
Installation work must be completed within the same amount of time. If this fails, change the number of grips or increase the duration of the masons’ work on the grip tier.
Arched lintels, unlike straight lintels constructed from standard elements, are made individually. That is why it is necessary to work out the arch in the project in detail: indicate the exact shape, lifting and span arrows, method of support, as well as manufacturing technology.
Arch-shaped lintels have been known to architects since ancient times. Arched structures, when vertical loads are applied to them, do not experience fracture loads - compression only increases in them. Traditional materials for arched ceilings are natural stone and solid brick. Today, when it is possible to use strong straight lintels, arches began to play only a decorative role. However, from an architectural point of view, arches have been and remain an indispensable technique for decorating buildings in the classical style and not only.
Arch designs are experiencing something of a revival these days. They are made from small-sized elements, and it must be said that today the character of the arches has somewhat departed from tradition. For quite a long time, arches were made of brick, as was the entire wall. The arch has always been load-bearing, but now it can be used exclusively to decorate the facade. There is no point in making such arches from solid brick, because it is much more convenient to use lightweight elements.
Without exaggeration, the very idea of an arched lintel can be called genius. Made even from ordinary rectangular bricks, it is integral and has a high load-bearing capacity. An arch can collapse only if its elements are calculated incorrectly. If the compressive strength of an element, in particular a brick, is higher than the compressive loads placed on it in an arched structure, then the arch will be unshakable.
Elements of an arched lintel Today, the most popular materials for laying arched lintels are clinker or sand-lime brick. By the way, analogues of sand-lime brick have been used for the construction of arches for more than a century. As you know, the strength of sand-lime brick is constantly increasing due to the permanent chemical reaction of carbon dioxide and calcium that are present in this material. Sand-lime brick combines well with other masonry materials, be it ceramics or cellular concrete blocks. With all this, sand-lime brick is relatively inexpensive.
Making arches
The masonry elements are connected in the arch using traditional cement-lime mortar. The seam between the rectangular elements has the form of a truncated isosceles triangle, the base of which is directed towards the upper arc. The minimum thickness of the arch seam is 0.5 mm, and the maximum is 2 mm.
When designing an arch, it is important to correctly calculate the number of its bricks. It depends on the width of the opening and the thickness of the wall. A bow arch always has an odd number of bricks because the topmost key brick divides it into two equal parts. For example, for an arch 12 cm thick and 150 cm wide you will need 21 bricks. If you reduce the number of bricks to 17, then the span width will be 120 cm.
To make a brick arch, circles are used - special support templates made for a specific arched structure. If the opening width is less than 120 cm, then it is convenient to make circles from a board cut along an arc. The circles are supported on both sides by temporary wooden supports (racks). For wider openings, circles are made from several boards held together. The thickness of the arch and its radius
Before starting to lay the arch, the bricks must be well soaked so that they do not draw in a lot of water from the mortar, because This can cause cavities to form in the seams. To make it easier to wash off the solution, the front side (archivolt) of the clinker brick can be opened with a water-repellent compound. After installation, the masonry of the arches is laid evenly on both sides, approaching the center.
Maximum thrust forces occur in the supporting parts of the arch, so it is necessary to lay the supporting bricks on the mortar with the spoon part perpendicular to the thrust forces. Exactly at the top of the arch, the masonry should meet the keystone, which is laid last and on a rigid mortar. The keystone has to be pressed into the masonry with considerable effort. You can’t score him with blows, because... vibration will disrupt the position of other elements.
Circles of a narrow arch Circles, as noted, rest on temporary stands. These racks must be wedged in order to loosen the wedges a little an hour after the masonry is completed. This technique allows you to compact the mortar in the seams, since the arch structure, when the supports are weakened, will already begin to work in compression. It will be possible to completely knock out the wedges from under the racks no earlier than in 5-6 days. 
Reinforced concrete arched lintels are also quite popular in modern houses. They can be monolithic or made from prefabricated elements. Such arches are made faster than brick arches and do not require special care. In addition, reinforced concrete can be used to create an arch that spans a very wide opening. Monolithic arches can have different geometries, which are not available to arches made of small elements. And, importantly, such arches are relatively inexpensive. The most difficult thing in their manufacture is the reinforcement.
Reinforced concrete arches can be made in two ways - in removable and permanent formwork. In the first case, a sealed formwork of the required shape is made and supported with temporary racks. The working rods of the arch are bent exactly according to the template and connected into a frame using knitting wire and transverse clamps. After laying the reinforcement cage, concrete is poured into the formwork.
Very often, a monolithic arch is combined with a reinforced concrete wall belt, which ensures that the structures work together to absorb loads. In this case, a common formwork is assembled, which allows both structures to be concreted simultaneously. It is also important to combine their reinforcement cages.
Spacers must be placed on the working reinforcement bars, which will provide the necessary protective 2-centimeter layer of concrete on the outside of the part. Another important point is correctly calculated arch supports. They cannot be less than 8 cm, but more often the supports are set at 15-20 cm.
Concreting of a monolithic arch is carried out in a continuous mode. The concrete mixture is compacted by bayoneting, but this must be done carefully so as not to disturb the position of the reinforcement elements. The formwork can be dismantled within 10-14 days after pouring the concrete, but the part will gain full strength only after 28 days.
Arches made in permanent formwork are made using U-shaped volumetric shaped elements made of cellular concrete. This solution is justified only for covering openings whose width is around 2.5 m. The U-shaped elements are joined together with an adhesive solution. A reinforcement cage is placed in the cavity of the formwork elements. Afterwards the whole thing is filled with concrete. The arch constructed in this way initially has an angular shape, since it consists of straight sections of U-shaped elements, the length of which is about 60 cm. However, it is easy to round it at the finishing stage. Using permanent formwork, you can also make a narrower arched lintel, but in this case it will be necessary to manufacture and fit a large number of elements to each other, which is quite difficult to do; in addition, this generates a large amount of waste. Thermoblock arch
Permanent formwork can also be made of polystyrene foam thermoblocks. They are light, cut well, and are connected into a lock. Arches made of thermoblocks are made, first of all, in walls erected using the permanent formwork method. But in principle, nothing prevents the use of thermoblocks for arches in mills made of 
traditional masonry materials. Above the arch made of thermoblocks, it is necessary to install a horizontal straight reinforced concrete lintel (core). The opening is made of thermoblocks, starting from about a height of 1.5 meters, but is not filled with concrete. After this, an arched opening of the required geometry is cut. Then all that remains is to close the lower open part of the blocks with a flexible gasket, which is supported from below by an already cut out semicircular segment. The groove for the cut-off gasket can be cut only on one side of the blocks, but so that a small groove is formed on the opposite side into which the far edge of the gasket will be inserted. The support posts can be removed after 14 days. Immediately after this, remove the gasket and remove the trimmed lower part. This is a very inexpensive and simple way to make an arch. Imitation of an arch in a wall made of cellular concrete
An arch over a door or a narrow window in a wall can be created from any masonry material using cellular concrete blocks cut along an arc. To do this, first a straight reinforced concrete lintel is made, and below it, blocks of cellular concrete are attached to a strong adhesive solution, possibly even with anchoring. This design is called a combined arch made of cellular concrete, but, in fact, is an imitation of an arch.
Arches are rarely used indoors today, because... in interiors they have gone out of fashion. However, some designers still include them in projects at the request of customers. The easiest way to make them is from plasterboard. This solution is not only easy to implement, but also makes it possible to very easily change the shape of the lintel above the door during the next repair.
Arched lintels
Arched lintelsLintels over openings can be made from ready-made elements. But arched ones have to be done individually. Therefore, in the project the arch must be developed in detail. After choosing its shape, lifting boom and span, you need to decide on the manufacturing technology. Arched lintels have been known since ancient times. Vertical loads in arched structures generate only compression forces, so they do not require additional reinforcement. For many centuries they were made from natural stone or solid ceramic bricks. Currently, due to the large selection building materials the practical structural merit of arches is not relevant. Nowadays the aesthetic aspect is more important, so arches serve as decoration for the facade of the house and give it a certain style.
Stone lintels
Arch designs using small-sized elements are experiencing a renaissance, but their character is changing. Once upon a time, the entire wall, including the arched lintels, was built from solid brick. Nowadays, masonry in the construction of arches is used to decorate the facade. Therefore, instead of a solid brick, they are more willing to choose a more spectacular and more
Expensive clinker brick. Instead of clinker bricks, you can use sand-lime bricks. Similar lime-sand products have been used for lintels for hundreds of years. The strength of this material increases constantly, thanks to the continuous chemical reaction of carbon dioxide with calcium, which is part of its composition. Sand-lime brick is easily compatible with other materials, for example, with cellular concrete or ceramics - masonry mortars ideally bind their surfaces. At the same time, sand-lime brick is relatively cheap.
How to do it. To connect masonry elements in the arch, only traditional cement-lime mortar is used. The minimum thickness of the seam is 0.5 cm, and the maximum is 2 cm. The number of bricks in the arched lintel depends on the width of the opening to be covered and the thickness of the wall. An odd number of bricks are placed in a bow arch, because the key brick must be placed strictly at the top of the arch. For an arch with a thickness of 12 cm and a span of 150 cm, you will need 21 bricks, and for a span of 120 cm, 17.
Before starting masonry work, carefully plan the placement of bricks in the arch. For openings up to 120 cm wide, the circles (the template on which the bricks rest when laying the arch) are made from a board cut to the shape of the arc of the arch. On both sides, the circles are supported on temporary racks made of timber and, with the help of wedges, are driven with blows to the desired location. For arches of large spans, circles are assembled and knocked down from several boards. Before starting masonry work, the brick is moistened abundantly.
The surfaces of clinker bricks that are not in contact with the mortar are lubricated with a special 
a water-repellent composition that makes it easier to wash off any solution that gets onto the surface of the visible side of the arch. The arch is laid on both sides simultaneously and evenly. In its supporting parts there are large thrust forces, so it is important to lay the lower, supporting bricks on the mortar with the spoon part perpendicular to the action of thrust forces. The masonry should end exactly at the top of the arch. The last key brick is placed on the hard mortar, pressing it into place. The castle brick cannot be delivered with blows. An hour after the completion of the masonry, the arches and wedges supporting the circles are weakened. This compacts the mortar in the seams, it is pressed harder against the bricks, thus eliminating voids in the mortar that can form as a result of water being drawn out of it by the bricks. After three to five days, after the mortar in the seams has completely set, the wedges are carefully knocked out and the circles are removed from under the arch.
Reinforced concrete lintels
In private houses, arched lintels made of reinforced concrete are the most popular. They are usually made monolithic, but can be assembled from ready-made shaped elements. this facilitates the construction of the arch and reduces work time. In traditional formwork. The joint work of steel and concrete provides a large load-bearing capacity of the lintel, which allows it to cover very wide openings. Other advantages of monolithic arches include: availability of their materials, low cost of work, proven simple techniques for making monolithic reinforced concrete structures, freedom to choose the shape of the arch and the possibility of using such a lintel in walls made of any material. But reinforcing a monolithic reinforced concrete arch is labor-intensive.
How to do it. A monolithic reinforced concrete arch requires the manufacture of sealed formwork of the appropriate shape and the installation of temporary supports under it. The working rods of the arch's reinforcement frame must be given the correct bend and connected with knitting wire to transverse clamps. Then, having laid the reinforcement frame in the formwork, fill it with concrete mixture. A reinforced concrete monolithic lintel arch is often combined with a reinforced concrete wall belt. To do this, their common formwork is assembled, the reinforcing frames of the belt and arches are connected, and at the same time they are concreted. This solution ensures that these elements work together to absorb loads. The arch reinforcement consists of upper and lower longitudinal rods connected by transverse clamps. It is necessary not to forget about spacers in the form of circles placed on the rods of the working reinforcement. They provide the required gap for the formation of a protective layer of concrete 2 centimeters thick. The correct size of the arch supports on the wall is also important, which cannot be less than 8-12 cm. But usually the size of the arch support is 15-20 cm. Concrete is placed in the formwork without interruption in work and care is taken to ensure that the components of the concrete mixture do not delaminate. Compacting the concrete mixture by bayoneting with a metal rod is done carefully so as not to accidentally damage the reinforcement. The concrete in a monolithic reinforced concrete arch lintel reaches its full strength after 28 days. But the formwork can be dismantled in 10-14 days.
In permanent formwork made of shaped elements made of cellular concrete. More in a simple way The construction of a monolithic reinforced concrete arched lintel is the use of ready-made shaped (U-shaped) elements made of cellular concrete instead of wooden formwork. Reinforcement and concrete mass are placed in their cavity. But such a solution is cost-effective only for arched lintels over wide openings, for which the span will be about 2.5 m. In openings of small width, obtaining a beautiful arc line requires a larger number of appropriately cut shaped elements, which leads to a large number 
waste that has nowhere to be used. How to do it. The shaped elements are cut at the required angle and, forming an arch, are connected to each other with an adhesive solution; reinforcement with spacers or plastic circles is placed in their voids to create a protective layer of reinforcement measuring 2 cm, then concrete is laid and compacted.
Shaped elements are permanent formwork. The supports under the arch are not removed for approximately 14 days, this is necessary for the concrete to set. The masonry of the wall adjacent to the arch is carried out in the same way as with brick lintels - the masonry elements are cut along the bend line of the arch, and the irregularities are filled with mortar. In permanent formwork made of thermoblocks. This is a very simple method with minimal waste. Thermoblocks made of polystyrene foam are lightweight, their installation is quick, and they are connected using locks. An arch using this technology can be made in walls not only made of polystyrene foam, but also from other masonry materials. To do this, a reinforced straight lintel is installed above the arch - the so-called core.
How to do it. In the opening at the height of the beginning of the arch arc (about 150 cm from the floor level), thermoblocks are placed, supporting them in the span of the opening on temporary supports. Above the planned arch, a shaped element made of polystyrene foam is installed - a permanent lintel formwork. Reinforcement is placed in it. Then, on the side surface of the blocks located in the upper part of the opening, an arch line is applied, along which a groove is cut in the blocks. Thanks to the supports, the entire structure is held in place. A metal spacer is inserted into the cut groove; it will prevent concrete from getting into the voids of the blocks located below the cut groove (below the arc of the arch). After this, the voids in the blocks above the spacer are filled with concrete, placing it in the lintel. Concrete, sliding along the voids of the blocks under the lintel, lingers on the gasket. This creates a monolithic arched lintel. After 14 days, the support posts are removed and the blocks located below the groove line (under the metal spacer) are removed. These blocks can be used later.
Combined arch made of cellular concrete
This is the easiest way, imitating a load-bearing arch. The vertical load here is carried by a prefabricated lintel. to which blocks of cellular concrete, cut to a specific shape, are glued from below. How to do it. Based on the size of the opening, the required standard lintels are selected, designed for walls made of traditional brick. Their use in walls made of cellular concrete or porous ceramics, to align the rows, requires laying cut blocks or monolithic concrete on the lintel, but ordinary brick can also be used. The cut blocks are attached with glue to the bottom plane of the lintels installed in the wall. An arch with a span of 120 cm requires two blocks. A wide opening requires more blocks. First, the layout of the blocks is planned, then they are cut with a hacksaw, and the final shape is given with a plane and a sanding float. Glue is also placed on the sides of the blocks adjacent to the slopes of the opening. The blocks are supported with racks while the glue sets (for 3 hours, and at low temperatures for 6 hours).
Laying lintels
Load-bearing prefabricated reinforced concrete lintels are used over openings to which the load from the floors is transferred. If there is no such load, to cover openings less than 2 m wide, reinforced concrete non-load-bearing or ordinary brick lintels are used in the form of masonry on high-strength mortars with reinforcing bars, under the bricks of the bottom row. Instead of ordinary ones, wedge lintels are sometimes made, which at the same time serve as architectural details of the facade. For spans up to 3.5...4 m, arched lintels are erected. This type of masonry is also used to construct vaulted ceilings (vaults).
When laying lintels, all longitudinal and transverse seams are completely filled with mortar, since such masonry works not only for compression, but also for bending. If the vertical joints are weakly filled with mortar, under the influence of loads, individual bricks may shift, and then the masonry may collapse.
Ordinary lintels are laid from selected whole bricks, observing the horizontal rows and ligation rules. The height of an ordinary lintel is 4...6 rows of masonry, the length is 50 cm greater than the width of the opening. For masonry, use a mortar of at least 25 grade.” The lintels are laid with formwork from boards 40…50 mm thick.
The formwork boards rest on bricks released from the masonry; After the formwork is removed, they are cut down. Sometimes the ends of the formwork are inserted into the grooves on the slopes of the openings (after removing the formwork, the grooves are filled with bricks). If the opening width is more than 1.5 m, then a stand is placed under the formwork in the middle or the formwork is supported on wooden circles (boards placed on edge).
In addition to plank formwork, inventory tubular supports-circles are used. They are made from two pieces of pipe with a diameter of 48 mm, inserted into a third piece of pipe with a diameter of 60 mm. When laying the pipes, the circles are moved apart so that the ends of the pipes of smaller diameter go inside the grooves left in the masonry. Two circles are placed on each opening; they can be used when window or door blocks are inserted into openings. With other types of circled blocks, they can be placed only after removing the lintel formwork.
Wedge and beam lintels are laid out of solid ceramic or silicate bricks with wedge-shaped seams, the thickness of which at the bottom of the lintel is not less than 5 mm, at the top no more than 25 mm.
Before laying the lintel, the wall is erected to the level of the lintel, simultaneously laying out its supporting part (heel) from hewn brick (the direction of the supporting plane is determined by the template, i.e. the angle of its deviation from the vertical). The masonry is laid in transverse rows on formwork supported by circles. Rows of masonry are marked on the formwork so that their number is odd, taking into account the thickness of the seam. The central brick in an odd central row is called a key brick.
Wedge and beam lintels are laid out parallel on both sides from the heel to the lock so that they are wedged in the lock by the central odd brick. The direction of the seams is controlled by a cord secured at the point of intersection of the mating lines of the supporting parts (heels). For spans of more than 2 m, the laying of wedge lintels is not allowed.
Arched lintels, arches and vaults are laid out in the same sequence as wedge lintels. The seams between the rows should be perpendicular to the curved line forming the lower surface of the arch and the outer surface of the masonry, widening at the top and narrowing at the bottom. The arrangement of the rows of masonry and the beds separating them are established in accordance with the first rule of cutting masonry, since in arches and vaults the force from the load acts tangentially to the curve of the arch and the bed of the rows are perpendicular to the direction of the pressure. Arched lintels are laid along the formwork from the heels to the lock simultaneously on both sides.
Formwork for laying vaults and arches should be lowered evenly when stripping. To do this, wedges are placed under the circles, and when they are gradually loosened, the formwork is lowered. The holding time for arched and wedge lintels in the formwork, depending on the outside temperature (in summer) and the type of masonry mortar for arched and wedge lintels is 7...20 days, and for ordinary lintels - 5...24 days.
For laying arches, vaults and their heels, Portland cement mortars should be used. The use of slag Portland cement and pozzolanic Portland cement, as well as other types of cements that harden slowly at low positive temperatures, is not allowed.
The laying of double-curvature vaults should begin no earlier than 7 days after the completion of the installation of their heels at an outside air temperature of not lower than 10 ° C. At an air temperature of 10 to 5 °C, this period increases by 1.5 times, and at a temperature of 5...1 °C - by 2 times. The laying of arches and vaults with ties, in the heels of which prefabricated reinforced concrete elements or steel frames are installed, can begin immediately after the installation of their heels is completed. The abutting edges of adjacent waves of doubly curvature arches are maintained on the formwork for at least 12 hours at an outside air temperature of at least 10 °C.
The construction of arches, vaults and their footings in winter conditions is allowed at average daily temperatures not lower than minus 15 ° C using solutions with chemical additives that ensure an increase in the strength of the solutions in the cold without heating. Waves of doubly curvature vaults, erected at sub-zero temperatures, are kept on the formwork for three days, after which they can be unraveled and the formwork moved.
Reinforced concrete and brick lintels are used in brickwork, the most common of which are reinforced concrete. Brick lintels, in turn, are ordinary and wedge-shaped, and wedge-shaped brick lintels are straight (or flat) and arched. Arched lintels are simply called arches and are distinguished by the height of the rise (or the length of the circular arc): arched, semicircular, lancet, etc.
Brick lintels have higher decorative qualities than reinforced concrete ones and are more suitable for brickwork. True, if the masonry is intended for further plastering or cladding, this advantage does not make sense.
The construction of brick lintels is more labor-intensive, especially when choosing a wedge lintel. As a rule, they are performed only by experienced masons.
If there is a narrow partition (less than 1 m wide) between two brick lintels, the laying of the rows between the lintels is carried out using the same mortar as the lintels. To make ordinary brick lintels, use a mortar of a grade no lower than M-25; for wedges - a solution of a grade not lower than M-10. The seams in the laying of lintels must be completely filled with mortar. Laying in a wasteland is unacceptable. The bricks used are selected (without defects), full-size, strength grades not lower than M-75. The laying of lintels always begins with bonded rows.
For openings with direct termination more than 2 m wide in individual construction, only reinforced concrete lintels are used.
Ordinary brick lintel
At the level of the top of the opening (when the masonry has been brought to this level), formwork is installed, for which strong boards 40-50 mm thick are usually used. The formwork is arranged taking into account the completion of a quarter along the upper edge of the opening (if a quarter is necessary). The formwork is supported in the grooves left when laying the slopes of the opening. Instead of furrows, it is possible to rest the formwork on bricks released from the masonry at the required level (based on the principle of creating a groove). If the opening is more than 1.5 m wide, the formwork is additionally supported by wooden posts (support beams firmly installed in the center of the opening). You can support the formwork only on beams, without grooves or brick outlets: in this case, two beams are installed on each side of the opening (and additionally in the middle if the opening is more than 1.5 m wide).
The solution is spread on the formwork in a layer of 20-40 mm. Reinforcement in the form of rods with a cross-section of 4-6 mm is laid on the mortar bed at intervals along the thickness of the masonry of half a brick (i.e., every half brick, the next rod is placed), but not less than three rods over the entire width of the wall (the interval between rods is reduced if the wall is thin). Under the future quarter (if there is one according to the project), additional reinforcement bars are laid. For corrugated rods (periodic profile), a diameter of 4 mm is sufficient; smooth rods must have a diameter of at least 6 mm. Instead of rods, you can use reinforcement in the form of steel strips with a section size of 1 x 20 mm. The strips are laid flat, according to the same principle as the rods.
The reinforcing bars are embedded (recessed) into the mortar to the same depth, so that they are approximately in the middle of the mortar bed along its thickness. The ends of the reinforcement on both sides of the opening must rest on the brickwork (not on the formwork) by at least 250 mm. Smooth bars must have bends (hooks) at the ends (an additional length is required to bend the ends of the reinforcement, and not the 250 mm mentioned above). These “hooks” are bent around the brick in the masonry.
Ordinary lintels over openings 1.5-2 m wide are arranged with a height of 5-6 rows of masonry; for openings of smaller width, a working lintel height of 4 rows is sufficient (the minimum height of a brick lintel is a quarter of the opening width). The seams in the lintel masonry must be strictly tied, both in the transverse and longitudinal directions.
When all 5-6 rows of masonry have gained sufficient strength, the board formwork is dismantled. On average, the formwork is removed 12-24 days after the completion of the lintel laying. The better the weather conditions, the faster the masonry will gain strength. Thus, at an outside temperature of up to 5 °C (but not less than 1 °C), you must wait 24 days before removing the formwork. At a temperature of +5...10 °C, the lintel is kept in the formwork for 18-24 days: at a temperature of 10...15 °C - 12-18 days; at a temperature of 15...20 °C - 8-12 days; at temperatures above 20 °C, 5 days are sufficient. These recommendations are given in the minimum acceptable time frame and are suitable only for ordinary and reinforced brick lintels in which there is no expansion due to the inclination of the stones.
After dismantling the formwork, the furrows into which it rested are filled with bricks or filled with mortar. If the formwork was supported by bricks released from the masonry, they are cut down.
Wedge brick lintel
To install a wedge lintel, like an ordinary one, install formwork boards and spread the mortar. In this case, there is no need to lay reinforcement. Bricks are used either ordinary or special, wedge-shaped (wedge-shaped).
The inclination of the bricks forms a spacer (wedge). The angle of inclination is calculated when completing the project and transferred to a template, which is then used when laying the lintel.
After installing the formwork, markings are made on it for the location of future rows of masonry, taking into account the thickness of the seam. Unlike conventional masonry, the bricks will be positioned vertically (i.e. almost vertically), and the markings will be made on a horizontal plane. The number of rows should be odd, and the middle row should be placed strictly in the middle of the opening. The central vertical row of bricks is called the castle row, since it closes the lintel masonry.
The brick is placed on an edge (on a poke or on a spoon) from the edges of the lintel to its middle, with a slope at the edges. The masonry is carried out simultaneously from both edges, with the obligatory bandaging of the seams between the rows. The correctness of the inclination is checked with a cord, the end of which is fixed at the place of the design intersection of the seams.
The middle brick is literally wedged into the masonry last (it should fit tightly between adjacent bricks, wedging the lintel and providing spacer). If necessary, the castle bricks are pre-ground. The middle brick, unlike all the previous ones, is installed vertically. In order to move from the calculated angle of inclination (at the edges of the lintel) to the vertical seams adjacent to the middle brick, the seams between the bricks of the wedge lintel when using ordinary bricks are arranged with a variable cross-section (in the form of wedges): in the lower part - at least 5 mm wide; in the upper part - no more than 25 mm. When using wedge bricks, the need to make wedge-shaped seams, as a rule, disappears.
Brick lintels are not used in the construction of buildings with likely uneven ground settlement. If the structure is on a soil foundation with uneven settlement, then even with the necessary expansion joints and the correct choice of foundation, it is better to make the lintels over the openings from reinforced concrete.
Wedge lintels are kept in the formwork (before its dismantling) for at least 10 days, depending on weather conditions. At temperatures up to 5 °C (but not less than 1 °C), the minimum holding period is 20 days, at temperatures of 5...10 °C - 15-20 days, at outside temperatures above 10 °C - 10-15 days.
A lintel is a small part of a wall that covers window or door openings. If the load, for example, from floors or other structures is transferred to the wall located directly above the opening, it is necessary to use special load-bearing prefabricated reinforced concrete lintels, which, among other things, can be do it yourself . If there is no such load, then to bridge openings no more than 1.5-2 m wide, lightweight reinforced concrete or ordinary brick lintels should be used in the form of masonry on a special mortar with increased strength with metal rods to support the bricks of the lower rows. Instead of ordinary lintels, wedge lintels are also used, which also serve as an architectural decoration of the facade of the object being built.
For the same purpose (architectural decoration of the facade), arched lintels are often erected for spans up to 4 m. Arched masonry is also used in the construction of floors in buildings; these floors are called vaults.
When laying lintels, it is necessary to completely fill all longitudinal and transverse seams with masonry mortar, since this masonry works not only to compress the lintel, but also to bend it. If all vertical joints are inappropriately filled with mortar, under the influence of loads, first a shift of its individual elements (bricks) occurs, and then complete destruction of the masonry.
Ordinary jumpers
Ordinary lintels should be laid only from selected whole bricks, observing the horizontality of the rows and all the rules for bandaging the seams of ordinary masonry. The height of an ordinary lintel is usually 4–6 rows of brickwork, and its length should be 50-55 cm greater than the width of the opening itself. For laying ordinary lintels, you need to use a solution of a grade not lower than M300.
Under the bottom row of bricks in the lintel, in a layer of mortar 2.5–3.5 cm thick, it is necessary to install metal reinforcement in the amount of one rod with a cross-section of at least 6 mm per area equal to half the brick. That is, there are two metal rods per brick, unless the project plan requires stronger reinforcement of the lintel.
The reinforcement laid in the mortar layer absorbs the tensile forces that arise in the masonry. The length of the metal reinforcement must be at least 70 cm longer than the width of the opening, that is, it must protrude 25 cm on both sides, and the ends are bent around the brick (example in Fig. 75).
Rice. 75. Laying ordinary lintels:
a – facade; b – section; c – masonry on plank formwork; d – masonry on inventory circles. 1 – reinforcing bars; 2 – boards; 3 – wooden circles; 4 – tubular circles
Also, ordinary lintels are made using temporary wooden formwork from boards 35-40 mm thick. A layer of mortar about 3 cm thick is laid on the bottom of the finished formwork, after which reinforcing bars are sunk into the mortar. This formwork must rest on bricks, pre-released bricks. After the formwork is removed, these bricks are simply knocked down.
Also, the ends of the formwork can be inserted into special grooves on the slopes of the openings; after removing the formwork, the grooves are simply sealed with mortar. If you need to make a lintel for an opening width of more than 1.3 m, then you need to place a stand under the formwork in the middle and secure it well.
Special inventory tubular supports-circles are also used. This design is made from two sections of pipes with a cross-section of 47 mm, built into a third section of pipe with a cross-section of 60 mm.
When laying circles, the pipes are moved apart so that the ends of a smaller diameter go inside the grooves previously left in the brickwork.
One opening will require two circles; their advantage is that circles can be installed even when window or door blocks are already installed in the opening. There are also other types of circles, when using which you can install blocks in the opening only after removing the formwork to make lintels.
Wedge and beam lintels
Wedge or beam lintels are usually laid out of ordinary ceramic bricks by forming wedge-shaped seams, the thickness of which at the bottom of the lintel should be at least 6 mm, and at the top, respectively, no more than 26 mm. The masonry is carried out in transverse rows on the formwork, which is held in place by circles. Before laying the lintels, the wall is erected to the level of the lintels. At the same time, its supporting part (heel) is laid out from hewn brick (using template the direction of the reference plane is determined, that is, the angle of its deviation from the vertical).
After this, the rows of masonry should be marked on the formwork in such a way that their number is an odd multiple, taking into account the thickness of the seam. In this case, the rows of masonry should be counted horizontally rather than vertically. The central, that is, odd row of bricks is called the castle row. It must be located strictly in the center of the jumper in a vertical position.
The laying of wedge and beam lintels is carried out simultaneously from both sides, that is, from the heel to the castle in such a way that it is wedged in the castle by the central brick. The correct direction of the seams must be checked with a cord secured at the point of intersection of the mating lines of the supporting parts (heels). The laying of wedge lintels is used only for spans up to 2 meters wide.
Installation of window lintels
Arched lintels and vaults
Arched lintels, as well as arches or vaults, are laid out in a similar sequence to wedge lintels. The seams between the rows must be perpendicular to the curved line that forms the lower plane of the arch, and accordingly to the outer surface of the masonry.
The joints of the masonry take on a wedge shape with widening at the top and narrowing at the bottom. This arrangement of the rows of masonry and the beds separating them corresponds to the first rule of cutting brickwork, since in arches and vaults the force from the load is redirected, acting on the tangent to the curved arch.
The beds of the masonry rows are perpendicular to the direction of the load (example in Fig. 76).
Rice. 76. Laying lintels:
The laying of the arched lintel is carried out using pre-assembled formwork of appropriate shapes and sizes in the same sequence as the laying of the wedge lintel. The direction of the radial seams of the masonry, as well as the correct placement of each row of the arch, is checked using a cord, which is fixed in the center of the arch being built. Using a cord and a square template, which has the outline of one of the sides corresponding to the curvature of the arch, the position of each of the rows of masonry is determined and checked.
Rice. 76 (continued). Laying lintels:
c – arched; d – masonry seams; 1 – direction of the reference plane; 2 – castle brick; 3 – cord; 4 – square template
The design of the formwork when laying vaults and arches must be such that they can ensure their uniform lowering when removed. To do this, it is necessary to install wedges under the circles, with their gradual weakening the formwork would lower evenly.
As for the holding time of arched or wedge lintels in the formwork, they directly depend on weather conditions and the brand of mortar that was used during the construction of the structures. So, in the summer, arches can be maintained for 5 to 20 days, but lintels can be maintained for 8 to 25 days.
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When building any house, it is natural to install doors and windows. It is clear that all four walls of the house will not be blank - openings for windows and doors must be left. If the opening width is expected to be more than 2 m, then they are covered with reinforced concrete lintels. If the width of a window or door opening is assumed to be less than 2 m, then such an opening is blocked by ordinary wedge or brick lintels.
Ordinary brick lintels
An ordinary brick lintel is masonry with mortar grade 25 and higher (high strength). It is a continuation of the wall masonry. To absorb tensile loads from the laying of the lintel, reinforcement with a diameter of 6 mm is used.
When laying the slopes of openings, grooves are left in them, into which the ends of the formwork are installed. The formwork is usually boards 40-50 mm thick. If the opening width is more than 1.5, it is good to support the moth formwork on wooden racks made of beams.
A solution 2-3 cm thick is spread on the formwork and the reinforcement is sunk into it. If the reinforcement has a smooth profile, then the ends of the rods are bent around the brick; if it is periodic, there is no need to bend the ends.
Reinforcement bars must extend into the masonry by at least 25 cm, with one reinforcing bar laid for every half brick.
After laying the lintel, the formwork is removed and the furrows are filled with brick or mortar.
If the outside air temperature is 10 0 C and higher, then the period of maintenance of an ordinary brick lintel is 12 days, if the temperature is lower - at least 24 days.
Wedge brick lintels
They are installed in the same way as ordinary lintels with an opening width of no more than 2 m. They can be made of ordinary and wedge-shaped bricks. Using ordinary brick, the masonry seam is made wedge-shaped with a thickness of less than 5 mm at the bottom and no more than 25 mm at the top.
Before laying the lintel, the wall is erected to the level of the lintel, while simultaneously laying out the heel (its supporting part) from hewn brick. The direction of the reference plane (its deflection angle) is determined by a template.
When laying out a wedge lintel, no reinforcement is used, and the laying is carried out using pre-installed formwork. Rows of masonry are marked on the formwork so that their number is odd. The central odd row of bricks is called the castle row.
The masonry is carried out in transverse rows, laying the brick on an edge from the edges to the middle of the lintel and with a slope at the edges to form a spacer (wedge). the brick should fit tightly into the locking row, tightly wedging the lintel.
A type of wedge type is arched brick lintels.
Arched brick lintels
To install an arched lintel, it is necessary to prepare a special formwork - a circle with a tie resting on the posts. Wedges are placed under the circles. When the wedges are loosened, the formwork lowers. The design of the formwork must ensure its uniform lowering when stripping
Bricks placed at the top of the arch form a castle. The seams between the rows of bricks must be perpendicular to the curved line forming the lower surface of the arch and the outer surface of the masonry. To check the masonry, use a square template and a cord attached to the center of the arch.
If ordinary rather than wedge bricks are used, then a wedge shape is given to the masonry joints from 5 mm down to 25 mm at the top.
It is necessary to maintain arched and wedge-shaped brick lintels in the formwork for 7 to 20 days, depending on the outside temperature and the brand of mortar.
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In modern standard construction Brick lintels are perhaps an outdated technology. However, if you decide to build a small palace (or a large castle) with vaults and arches, then this article will be useful to you.
Lintels are structural elements that span window or door openings. The width of the opening covered by the lintel is called the span. Most often, openings are covered with factory-made prefabricated reinforced concrete block and slab lintels. Sometimes the openings are covered with brick structures: ordinary, wedge, beam and arched lintels. Ordinary jumpers - these are rows of masonry reinforced with reinforcement at the bottom. The laying of such jumpers is carried out as follows. A layer of mortar (composition 1:3) 2 cm thick is spread over the formwork, reinforcement is laid from four rods with a diameter of 5...6 mm (for a wall thickness of 2 or 2.5 bricks); the bent ends of the reinforcement are laid into the masonry 250 mm on each side. The laid reinforcement must be covered with mortar on all sides.
Ordinary lintels with a span of 1 to 2 m are laid on mixed mortars of grade 25 and higher.
Wedge jumpers (Fig. 56, a) are laid out from bricks laid on edge. In such lintels, the brick located in the center is called lock 1, and the supports are called the fifth 2.
Beam segmental lintels (Fig. 56, b) unlike wedge lintels, they have a rise f (height from the bottom of the lock to the bottom of the heels), which is expressed in fractions of the span, for example 1/10, 1/12.
If the radius with which the lintel is drawn approaches half the span of the lintel, then such a lintel is called an arch.
Semicircular arched lintels (arches) (Fig. 57, a) have the shape of a semicircle (their supporting heels are located at an angle of 30° to the horizon); box arches(Fig. 57, b)- more flat, with a lifting boom f of less than half the span. The maximum span of arches is up to 4.5 m.
The laying of arches, wedge-shaped and ordinary lintels is carried out using formwork. For ordinary and wedge lintels, wood-metal formwork is used - panels 40 mm thick. With a span of up to 1.5 m, the formwork is supported on masonry extensions 6 cm long from two rows of bricks, which are cut down after the formwork is removed. In spans of more than 1.5 m, the formwork panel is supported by wooden posts.
The arches are laid along circles cut from boards shaped like the lower outline of the arch. The circles are made up of individual jambs, knocked together in two layers with the joints spaced apart. The formwork is sewn on top of the circles with nails, along which the masonry is laid.
The laying of wedge lintels begins from the heels to the middle and ends with a lock; the number of bricks laid must be odd. The thickness of the vertical seams at the top of the lintel is up to 25 mm, at the bottom - at least 5 mm. The maximum span of wedge lintels is up to 2 m.
The timing of stripping the lintels is given in table. 45.
Vaults Unlike arches, they cover not individual openings, but entire rooms. The most common are barrel vaults resting on two parallel walls. The vaults are laid out of brick on formwork 5 (Fig. 58) with a continuous plank flooring. The laying is carried out in separate sections, simultaneously from the heels to the top. The radial position of the seams is controlled with a square template. The laying of the section is completed by wedging the vault with key bricks. You cannot walk on the laid out part of the vault and store materials on it. The formwork of the vault is carried out after 10…20 days.
Arches and vaults transfer a horizontal load, called thrust, to the supports. If the amount of expansion is significant, then install steel ties anchored in the supports.
For masonry smoke ducts and pipes Only ceramic bricks of the correct shape, normal firing, and without cracks are used. The quality of the brick is determined by lightly tapping the hammer (it should not ring) and by appearance. The first two rows of chimneys are laid out, as with a single-row ligation system, the subsequent ones are made of bricks laid in spoons. To ensure dressing, an incomplete brick is used. The dimensions of the chimneys are 140x140 and 140x270 mm. They are placed vertically and separated from one another by 1/2 brick cuttings. Chimneys inside the building take the form of separate risers or are placed in internal stone walls. Ventilation ducts are located between the smoke ducts to improve the circulation of heated air. They can also be made from sand-lime brick.
Chimneys in one-story buildings are laid out on clay-sand mortar, with a height of more than one floor - on lime-sand or lime-cement-sand mortar. For clay-sand mortar, sifted sand is used, since the greatest strength of the masonry is ensured when the joint thickness is no more than 5 mm.
The thickness of the seams for laying pipes using lime or complex mortar is no more than 10 mm. Laying on clay-sand mortar is carried out, completely filling the seams. Every four to five rows of masonry, remove excess mortar in the seams with a wet brush or rag. It is not allowed to lay the brick with the hewn side inside the channels or to level the internal surfaces of the channels with mortar. Smoke channels are separated from combustible structures by air gaps or insulated with non-combustible materials.
Chimneys within the attic or above the roof are laid out with lime or complex mortar. Within the attic they are plastered.
Round Andrectangular wells for water supply and sewerage systems - structures built from brick. For a water supply network of pipes with a diameter of 50...600 mm, round wells are used with a working part height of 1.8...3.3 m, a diameter of 1...2 m, as well as rectangular wells with a working part height of 1.8...3.9 m and dimensions in plan from 2X2.5 to 3X3 m. Depth of wells 2.5...4 m. Thickness brick walls depends on the depth and soil conditions and lies within 12...77 cm. For sewer network from pipes with a diameter of 150..1200 mm, round wells are used with a lower diameter of 1...2 m and an upper diameter of 0.7...1 m. The height of the working part is 0.9...2.7 m, the height of the neck tapering with a cone is 0.65...4 m .For masonry sewer wells Ceramic bricks and cement-lime or cement mortars are used.
Before laying a well, a concrete base 10...15 cm thick is laid on compacted soil. After laying and hardening the concrete mixture, the well is marked on the base: for a round well, its center and inner circumference are marked, for a rectangular well, the longitudinal and transverse axes, internal and external edges are marked walls Then the brick is prepared and laid out, the mortar is spread and the brick is laid in the usual sequence.
Round wells are laid out in studded rows. The bricks are placed so that their butt faces form the inner surface of a well of a given diameter. The dressing of the masonry is done by moving bricks in adjacent rows by a quarter of a brick. Vertical joints on the inner surface of the masonry must be completely filled with mortar. Significantly widened seams on the outer side of the masonry also need to be filled well, especially when constructing wells in wet soils.
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This concept designates a specific area. The function of lintels is to bridge openings. There are:
- privates;
- wedge-shaped;
- arched
If the bridge structure does not take the load from the floors, then reinforced concrete masonry can be used. The mixture can only be used with improved strength. If the wall above the lintel is loaded, then prefabricated structures are required. A prerequisite is the uniform filling of longitudinal and transverse seams with mixtures. If this requirement is not observed, the consequences can lead to shifting and even destruction of the masonry. Because in this case, the arches are subject to both compression and bending loads.
Let's consider each type of device separately
Ordinary jumpers. The mortar used for this type must be mixed from cement, grade higher than 25. Select whole bricks must be used as the material. The dressing rules apply as for ordinary masonry. (Read about other types of bricklaying here) The maximum height of the brickwork should consist of 4-6 rows, and the length should be 50 cm greater than the size of the opening over which the laying work will be carried out. The structure must be reinforced with rods with a diameter of at least 6 cm. Required amount there must be at least three. The rods should be laid under the bottom row in mortar, the size of the seam between the bricks is 2-3 cm. For this, formwork made of boards 50 mm thick is best suited. A solution is spread on them into which the rods are installed. Bricks are used as support for the formwork, which are released from the masonry specifically for these purposes. Once the work is completed and the mortar has hardened, the formwork is removed and the bricks are cut down. Reinforced brickwork must have reinforcement ends that extend at a distance of 25 cm and are bent around the brick. In this way the structure is anchored. The laid lintel is maintained for 5 to 24 days at summer air temperatures.
Wedge jumpers. Typically, work is carried out in rows, rows arranged transversely to form wedge-shaped seams. The width of the brickwork joint must be at least 5 mm at the bottom and not exceed 25 mm at the top. The execution sequence is as follows:
- the wall is erected to the point where the lintel is made;
- formwork of the required shape and size is installed;
- rows are marked on the installed device, their number must be odd. The central row of bricks is called the castle row; it should be in the middle of the lintel and located in a strictly vertical position;
- round brickwork is carried out simultaneously on both sides and is closed with a central odd brick;
- Using a cord, the correct installation is checked.
Important point! Wedge lintels are not allowed when laying spans of more than 2 meters.
Arched lintels. This includes making arches. The work process is repeated as in the previous case:
- the wall is erected to the construction site;
- the formwork design is set up, which should provide for uniform lowering when dismantling it;
- The rows must be marked out in an odd number;
- The brickwork is closed in a semicircle by a central odd brick. Such work must be carried out simultaneously;
- Using measuring devices, the correctness of the work is checked.
In this case, the inter-row seams should be perpendicular to the lower generatrix of the arch and the outer surface. The seams between the rows will be in the form of wedges, widening at the top and narrowing at the bottom.
The period of curing of wedge and arched lintels until strength is achieved in summer ranges from 5 to 20 days.
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Types of brick covering openings
A lintel is the covering of a door or window opening. Reinforced concrete lintels are most widely used in construction. They can span long spans and withstand heavy loads.
Brick lintels are used only for non-load-bearing walls, as they do not have sufficient strength for this. The span width should not exceed 1.7 m.
1 - private; 2 - wedge-shaped; 3 - arched; 4 - arched beam
Ordinary brick lintels are called ordinary lintels. The bricks in them are supported by reinforcement. Wedge, bow, lancet, arched, semicircular and box lintels are used as an architectural detail of facades.
1 - semicircular; 2 - lancet; 3 - box
Their variety is determined by the shape of the opening, or more precisely, the outline of its upper part. According to the principle of an arched lintel, vaults are laid out, which are the ceiling of buildings.
Before the invention of concrete (late 19th century), openings were covered with brick lintels. It was not only a tribute to beauty. Wedge and types of arched openings held the load from the wall due to the expansion, which ensured the fan arrangement of the bricks in the masonry.
In temple architecture, arches and vaults, as a way of covering openings and rooms, over time became the canon of church architecture. Modern brick arched openings and vaulted ceilings are only an architectural solution.
The use of arched or wedge lintels is necessary when reconstructing buildings and structures of the 17th-19th centuries.
Stoves and fireplaces are still being built in almost every country house, where arched or wedge-shaped lintels and cylindrical vaults are often used when constructing a basement or guardianship.
Ordinary jumpers
Ordinary lintels are made according to the principle of ordinary brickwork. It is also carried out with dressing and ensuring horizontal and vertical seams. Its difference from simple masonry is the observance of a special quality of work. Careful filling of the seams is necessary to create a joint work of all the bricks covering the opening.
Ordinary lintels, unlike ordinary masonry, not only compress under the weight of the overlying wall, but also bend, having no support in the opening. The size of the brick lintel is taken based on its bending performance in the opening. The height is 5, 6 rows of masonry. In length, the size is calculated by the width of the opening plus 500 mm on each side of it.
Due to the special importance of the design of the ceiling of any opening, the brick selected for masonry is selected, the grade of mortar used is no lower than 25. In an ordinary lintel, the brick rests on reinforcement, which is embedded in a layer of cement-sand mortar.
Reinforcement is assigned by calculation and depends on the magnitude of the load on the opening. For small values, the reinforcement is installed structurally from round steel with a diameter of 4-6 mm. Its quantity is one rod per half brick of the wall. The reinforcement must extend into the masonry beyond the edge of the opening by at least 250 mm. Their ends are bent upward around the brick.
1 - fittings; 2 - solution; 3 - formwork
To install an ordinary lintel, like any other, you will need a tool that is used for ordinary brickwork. To make reinforced support for bricks, it is necessary to install formwork. It can be made from boards 40-50 mm thick.
You can avoid mortar leakage and give the bottom of the lintel a more even appearance by laying any roll waterproofing or simple plastic film. It must be remembered that unevenness on the surface of the formwork will affect appearance the top of the opening.
A mortar layer is spread on the formwork, on which reinforcing bars are laid and embedded into it. Then a second layer of mortar is laid, which covers the reinforcement. It is important to observe the thickness of the protective layer for metal products. It is at least 3 cm.
When hardening, the solution must gain the necessary strength so that further laying of the lintel can be carried out. The period of keeping it in the formwork is at least 12 days in the summer, in the fall - at least 20 days. During periods of negative temperatures, it is necessary to observe special measures developed for winter masonry.
To support the formwork, bricks are made from the masonry, which are subsequently cut down after the mortar has gained full strength and the boards have been removed. You can make a furrow in the masonry and insert formwork into it, after removing which a brick with a masonry joint is installed in this place.
1 - formwork; 2 - brick release
Large openings (wider than 1.5 m) require the installation of racks under the formwork. You can install the support boards under the flooring on the edge for rigidity.
Wedge jumpers
Wedge lintels do not require reinforced mortar support. The load-bearing capacity of such a lintel occurs due to the expansion in the wedge-shaped installation of the brick.
Exists for the option of installing wedge jumpers:
- wedge-shaped vertical seam masonry;
- wedge-shaped brick.
In the case of a wedge-shaped seam, its thickness at the bottom is taken to be at least 5 mm, and at the top - no more than 25 mm. If wedge bricks are used, the joint in the masonry is made of the same thickness of no more than 10 mm. Wedge lintels are installed using formwork with circles.
If a window or doorway is placed with quarters, then to construct a wedge lintel you will need three circles. One is made shorter and installed at the level of the quarters, the other two - inside the opening. Longer circles are covered with formwork, which can be made from boards.
The wall is laid to the level of the upper part of the lintel with a heel (support) device. In this case, the angle of inclination of the edge of the lintel (bricks) relative to the vertical is immediately determined. Next, you need to mark all the rows on the formwork of the future floor. Their number must be odd. When calculating the design of each row, it is important to take into account the thickness of the seam.
The central brick row is inserted vertically and acts as a lock. It creates compression in the lower part of the lintel and makes it possible to withstand the overlying load without reinforcement.
1 - lock; 2 - heel
They begin laying the wedge lintel from the heels to the middle on both sides, in order to ultimately approach the central brick - the castle. You can maintain the exact direction of each seam by finding the point of intersection of the direction lines of both heels. A nail is driven into this place on the formwork and the line of each seam is determined using a rope tied to the nail.
Arched lintels, arches and vaults
The principle of constructing arched ceilings of openings and vaults does not differ from the laying of wedge lintels. The shape of the arch can be arched, lancet, semi-circular, or box-shaped. They differ in the choice of center, segment size and circle radius.
In any embodiment, the center line of the seam is perpendicular to the inner surface of the lintel or arch. The curved line is formed due to the wedge-shaped joint or wedge-shaped brick. In the case of an arched opening, the center line of the seam is a continuation of the radius of the curve.
Calculation of the arched lintel: 1 - onion arch; 2 - semicircular arch; h—arc height; s is the width of the window or door opening; r — arc radius
The thickness of the seams is taken as in wedge lintels:
- minimum 5 mm - for the bottom of the vertical seam;
- maximum - 25 mm - for the upper part.
1 - lintel brick; 2 - wedge-shaped solution; 3 - castle brick; 4 - circled
The formwork shape is made in accordance with the selected floor shape. Checking the radial direction of the seams and the correct curvature of the arches is done with a rope tied to the center of the circle of each section of the lintel. You can make a template-gon for the desired outline of a semicircle or segment.
Arches are laid out according to the principle of an arched lintel. Vaults are erected today during construction public buildings, churches or temples. To construct them, continuous formwork of the required shape is made. Cylindrical vaults are often laid out in a “Christmas tree”. The masonry is carried out simultaneously parallel to the axis of the arch and in rows at an angle of 45°.
Wedges are placed under the formwork, which are gradually removed when stripping the formwork to ensure its uniform lowering. Fresh masonry is very sensitive to loads. You cannot place containers with mortar on it or place bricks for masonry. This can lead to distortion of the shape of the ceiling and disruption of the bonding of the brick and mortar.
Vaults and arches of complex configuration require highly qualified masons, and it is better to entrust the work to a specialist. Having understood the intricacies of the technology of brick ceilings for openings, the construction of lintels and arches of a simple configuration will not be difficult.
Brick lintels, arches and vaults that came from the past, and today decorate the facade of the house, fencing, small architectural forms, fireplaces and stoves, harmoniously fitting into the interior or exterior of almost any architectural style.
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Arched
Concrete lintels, of course, are simpler and more reliable, but sometimes you want to decorate your house. And nothing adds sophistication to a building better than beautiful windows. Especially if they try to give the cottage the appearance of a castle. In such buildings, the owners even try to make the windows look like loopholes.
In this and in many other cases, non-standard shaped windows with a rounded top are installed in the building. For such windows it is necessary to prepare a special type of window lintel.
Onion
First, a little theory. Arched and beam lintels differ in shape. More precisely, the shape of both types of window lintels is rounded. Only the arch is almost a complete semicircle. And the beam lintel has the shape of a trimmed semicircle.
The space that the jumper covers is called the span. An arched or beam-type lintel always rests on two bricks, which are called “heels”. The number of bricks in lintels of this type is always odd. The top odd brick is called the castle brick.
Such lintels are usually made using solid ceramic bricks. It has a high degree of fire resistance, high heat resistance and allows you to ensure optimal humidity in the room. Therefore, only in some, exceptional cases, sand-lime brick is used for laying lintels.
Cement-sand mortar is used to fasten the bricks together. Such a solution is prepared from a mixture of sand and cement in a ratio of 1:4 (cement: sand). Cement is usually used M-400 with or without additives.
In addition, you can use dry construction “masonry mixture” to lay the lintel. This will significantly reduce the time for mixing the solution.
Tool
You will need a standard mason's tool: a trowel, a mortar box, a mason's hammer.
Manufacturing of formwork
Work on the manufacture of formwork for installing the lintel begins after the wall has been raised to the required height.
In order to independently lay a beam or arched lintel, you must use a special form made of wood, which is called a circle. It is raised to the level from which the masonry will be made and secured.
The circle is supported by two vertical wooden posts that are adjacent to the walls. The racks are spaced apart using special spacers.
The number of bricks for laying the lintel should be calculated in advance. A template is made to fit the dimensions of the lintel, using which we will know exactly how and what kind of brick is to be laid in the lintel.
To do this, a brick is installed at the very top (middle) of the template. A compass is adjusted to the width of this brick (adjusted for the thickness of the seams). Thanks to this device, you can calculate the exact number of bricks needed to install the lintel.
Work on laying the lintel begins from the heels. Based on the template, the outermost bricks are installed on the circle. The laying is carried out alternately on both sides - from the heel to the lock.
The seams are immediately filled with mortar. Excess solution is removed.
Work must be carried out as quickly as possible so that the solution hardens evenly. At the same time, it is necessary to carefully ensure that the bricks stand in accordance with the template.
At the top, the lintel should end with the last odd brick (lock), which allows the structure to be jammed.
Vertical control of work is carried out using a plumb line. Accuracy of laying along the radius is carried out using an improvised compass. From time to time it is worth applying a lath to the structure.
Dismantling of formwork
After the solution has dried, the formwork can be disassembled, starting with the vertical posts. Lastly, the circles are dismantled. But there is no need to rush to dismantle the structure. Let the solution dry thoroughly.
The result will be a beautiful lintel under the original window. But this work is still for a good mason. An amateur can try to do it, but it is not a fact that the time spent on such a jumper will not be wasted.
It seems that a self-respecting owner should correctly assess his strength.
Brick lintel diagram
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