The strength of a roof is the total strength and quality of all its constituent elements: rafters, beams, ridge girders and sheathing. And also how tightly and competently these elements are connected to each other. After all, almost every one of us is capable of understanding the cross-section and calculation of the roof load, but how can we secure the rafters so that the roof serves faithfully for at least half a century?
In fact, this is a whole science, and each type of roofing assembly has its own pros and cons, and the same type of fastening can have a very different effect on the strength of different roofs. Therefore, let's approach this issue with all responsibility!
Types of rafter systems according to the level of load on the nodes
There are two types of rafters - layered and hanging. Main design features:
Hanging rafters are distinguished by the fact that their upper ends always rest against each other and there is no support under their junction. And in order to balance the load from the roof, the lower part of their rafters is connected with another element - a tie.
The result is a regular triangle, in which only the lower element works to stretch. Another beam in the roof, where the rafters also need to be attached, is called a beam. It is located horizontally and supports the ridge girder.
Types of support units by level of rigidity
It is those places where the rafters are attached to the roof elements that are called the support unit:
The support unit is not always static - sometimes it has to be made movable if some structural element is subject to unstable loads. It's like a car wheel that compresses, spins, squeezes and turns.
Something similar is realized in support nodes, only the degree of freedom in them can be different - from zero, when the node itself is already motionless, to triple, i.e. maximum:
- Support node with zero degree of freedom. Both ends in this case are rigidly fastened with corners on both sides. A rafter on a beam or mauerlat with such a knot cannot move at all.
- Hinge joint with one degree of freedom. In this case, the beam has the ability to rotate in a circle.
- Hinge joint with two degrees of freedom. Now, in addition to circular rotation, there is also the possibility of displacement. This provides special fastening of the rafters to the mauerlat or beams, and you only need to install the sliders or slides.
- Hinge joint with three degrees of freedom allows the beam to move both horizontally and vertically. True, circular rotation may or may not happen here.
Comparing fasteners
These metal corners are used for attaching rafters to the mauerlat, beams and walls:
Types of metal plates
Note that there are two types of such plates: nail and perforated.
Perforated ones have many holes for bolts and screws, and it is with their help that such plates are attached to wood. The advantage of perforated plates is that they are able to connect the necessary elements of the rafter system at almost any angle. Moreover, such plates can be easily cut to the required size. Install perforated plates on both sides of the connections.
Nail plates do not have nails themselves. This fastener is used only in factory conditions, or in the presence of a special press. The fact is that you cannot hammer such a plate into the rafters with a hammer - you need proper, uniform pressure.
Additional items
Sometimes, in addition to the same metal corners and nails, support bars are additionally used:
And also like this:
If you use flat or shaped steel fasteners in joint connections, then:
- The thickness of the wooden elements should not be less than 5 cm. All because of the screws.
- Secondly, simple nails cannot be used here - only screw or rough nails, which simply won’t come out. Especially if the wood for the rafters has a moisture content of more than 18%, i.e. not completely dried, and after this material dries, the nodal connections are always weakened.
- Thirdly, take nails with a diameter of at least 4 mm and a length of at least 40 mm.
- Always use two angle irons per assembly if possible. Just place them symmetrically.
Attaching rafters to floor beams
Floor beams sometimes act as a kind of alternative to tightening. Most often this happens during the construction of light attics - it’s more convenient. But you can only attach rafters directly to the floor beams if you are confident in the reliability of the walls of the house. Because in this case there is no Mauerlat, and, as a result, the load on the walls is not distributed evenly - now it is point-loaded. And this is worse, of course.
By the way, it is not necessary to take thick beams for floors; a section of 5x15 cm is enough. Your main task is to make such a fastening so that the rafters do not begin to slide along the beam.
By the way, there is a big difference in how to attach the same rafters to the floor beams of single-pitched and gable roofs. So, the greater the load the roof experiences, the fastening should be done with a double tooth, while for single-pitched roofs one is enough. By the way, a double tooth usually has two spikes.
The most durable fastening is obtained if you make a notch, and with an additional tenon, which will also prevent lateral shifts of the rafters due to loads. On the other hand, it is important not to weaken the beam itself at the same time. Therefore, the cutout for the rafters should be made no closer than 25 cm from the edge (this will also help to avoid falcons), and only 1/3-1/4 deep from the thickness of the beam itself:
To ensure that the rafter leg does not slide off the mauerlat, a special recess is made in it. And in the Mauerlat itself, sometimes they make another one, a counter one - this is only more reliable, and the stubborn lock turns out to be strong.
True, the Mauerlat itself will be significantly weakened by this - take this into account. You can do something like this with it only when the Mauerlat is made of hard hardwood and has good strength.
The grooves alone will not hold the rafters in place, so be sure to additionally use metal fasteners. If your connection is stationary, it will be enough to drive nails at an angle, and for more unreliable structures, use clamp connections and metal plates. Forged wire, which is mounted into the wall for these purposes, will also help.
Another type of fastening of rafter legs to beams is bolted:
- Step 1. At the end of the beam that protrudes, make a triangular cutout. The hypotenuse of the cutout should be at the same angle as the angle of the rafters.
- Step 2. We also saw the lower part of the rafter leg at the same angle.
- Step 3. We place the rafter on the beam with a cut and fix it with nails.
- Step 4. Perpendicular to the rafter leg, we drill a hole for the bolt - through, so that the bolt can be entered from below through the cutout in the beam.
- Step 5. We put a washer on the bolt and tightly fix the entire assembly with a nut.
Upon completion of fastening, be sure to check the strength of all connections.
Attaching rafters to the wall
But not all rafter structures use a Mauerlat. Then how to attach the rafters to the wall itself? It’s simple: we find a replacement for the Mauerlat and work with it.
For example, in frame construction The frame beams on which the sheathing is made act as a mauerlat:
If for some reason you have to attach the rafters directly to the wall, without a Mauerlat, then you definitely need to make a tightening - a board or beam that will connect the rafters into one and take on part of the tension.
Such fastening is not always possible at all. For example, foam and gas blocks are bad not only because they easily transfer their moisture to wooden beams. They don't hold fastenings at all. You can easily pull out the same nail, driven 10 cm into a block, with your hands - then how to secure the rafters? Plus considerable pressure from the roof rafter system on such fragile walls. Therefore, there is no way to do without a Mauerlat.
We attach the rafters to the mauerlat
In any roof truss structure, the rafters are placed with the lower end on the mauerlat, and the upper ends are connected at the roof ridge. Mauerlat is a special beam that is laid along the perimeter of the external walls. It is designed to support load-bearing rafters.
Now let's figure out when the rafters rest on the mauerlat, and when - only on the walls:
- If the walls are made of concrete, brick or foam block (in principle, any materials that are capable of transmitting moisture), then the rafter legs cannot be rested on them. Otherwise, the entire roof will quickly begin to rot. That’s why we use timber, called Mauerlat, and separate it from the wall itself with any roll waterproofing.
- In log and cobblestone houses, a Mauerlat is no longer needed for the rafters - it is enough to make notches in the top beam and use additional fastening in the form of metal corners and brackets.
And depending on whether the house shrinks, they make a rigid and sliding fastening of the rafters to the mauerlat.
Method #1 - rigid mount
To provide a rigid, immovable fastening to the unit, you have two options. The first is to use special corners with hemming bars and special cuts on the rafter leg. The rafter here is fixed with corners on both sides, and therefore can no longer move:
In the second method, which is more common, you need to hammer the nails at an angle to each other. In the Mauerlat they are crossed, and the third nail is driven vertically:
Two nails on the sides hold it in place rafter leg from a left-right shift, and the top nail already attracts the rafter to the Mauerlat itself.
Or use long screws instead of nails:
Method #2 - fastening with one degree of freedom
But in this design, a certain movement of the rafters under the pressure of the entire roof is already allowed:
But let us immediately note that if we are talking about the ability to move horizontally, we are not at all talking about the fact that the rafter will literally “ride” along the beam. This is just a small opportunity to move by millimeters due to dynamic loads and temperature and humidity changes. Moreover, the slider will move only under maximum permissible loads, and you will not be able to see such changes with the ordinary eye.
The possibility of some movement remains even when fastening the knot with nails - if there are not many of them. But those hammered in a checkerboard pattern with a certain force will no longer allow the rafters to move.
Finally, to secure the rigid fastening of the rafters to the mauerlat, additionally use wire or anchors. You just need to think about this in advance:
Or here's another great visual example:
Method #3 - sliding mount
A sliding mount is a mount that has two degrees of freedom. That is, in simple terms, one of the two elements has the possibility of displacement:
And this makes sense. Thus, those rafters that rest against the mauerlat with a notch, and against each other from above, evenly transfer the load from the roof and the snow on it to the walls. But those rafters that are supported by horizontal notches on the mauerlat and on the ridge girder are called a non-thrust structure.
As we have already said, a sliding mount, even with three degrees of freedom, does not actually mean that the rafter will move loosely back and forth on the support. All this is only for invisible physical laws.
It is usually used only under severe dynamic loads on the roof.
Method #5 – splicing with fillies
To install roof overhangs, you also need to make fillies from boards, 50x100 mm in cross-section and such a length that it is equal to the overhang plus another 0.5 m for the junction with the rafters.
Then everything is simple: nail the fillies to the rafter legs and extend them beyond the roof. Are you wondering why this rafter element is called that? They just used to be cut in the shape of a horse - for beauty. And often today too.
The reliability of the roof structure directly depends on how correctly its entire supporting system is installed. And its main elements are rafters. The entire system consists of rafter legs that support and expand additional elements, such as struts, crossbars, side girders, support posts and braces. The rafter legs are connected on a ridge beam from above, and their lower edges very often rest on a beam fixed to the side load-bearing walls of the building.
Since the Mauerlat bears the heaviest load, it is made of powerful timber. Its cross-section is determined by the massiveness of the entire rafter system, but generally the size ranges from 150 × 150 to 200 × 200 mm. This load-bearing element is designed to evenly distribute the load from the entire roof and roof structure onto the load-bearing walls of the building. The rafters are attached to the mauerlat in various ways. They are selected locally depending on the type of rafter system (which can be layered or suspended), its complexity and massiveness, and the magnitude of the total loads to which the entire roof structure will be subjected.
Types of connecting nodes “rafters - Mauerlat"
First of all, there are sliding and rigid fastenings of rafters to the Mauerlat.
1. The sliding mounts consist of two individual elements, one of which has the ability to move relative to the other.
These fasteners can be of different designs - closed and removable.
- A closed mount consists of an angle, which is attached on one side to the Mauerlat, and on the other side has a special slot-like eye. A metal loop with holes for fastening to the rafters is installed in it. Thanks to the free, unfastened vertical side of the corner, the fastening allows the rafters to move slightly if necessary, without having a deforming effect on the walls of the building.
- The open fastening is designed according to the same principle, and differs only in that the metal loop is not inserted into the eye, but simply the upper part of the vertical shelf of the angle bends down after installation, thereby fixing the connection.
Video: example of installing a movable mount on a rafter leg and mauerlat
2. There are many more types of rigid fastenings. They are selected depending on the massiveness of the wooden structural elements and the method of installation on the Mauerlat.
This includes metal corners of different sizes, LK fasteners that will securely fix the rafter, installable by sawing it down without damaging it with fastening screws or nails.
- LK fasteners are produced in several sizes, so they can be selected to suit any thickness of bar or board. The thickness of the metal from which these fasteners are made is 2 mm, no matter what size they are. Depending on the size, fasteners have different designations.
| Designation | Size in mm |
|---|---|
| LK-1L | 40×170 |
| LK-2P | 40×170 |
| LK-3L | 40×210 |
| LK-4P | 40×210 |
| LK-5L | 40×250 |
| LK-6P | 40×250 |
It should be noted that these fasteners are suitable not only for connecting rafters to the mauerlat - they are also used for fixing the “floor beam - mauerlat” assemblies.
The main advantage of this fastener is the maximum rigidity and reliability of the connection of wooden elements.
- Fastening rafters with a cut to the Mauerlat using corners is carried out on both sides, which ensures the required rigidity.
There are corners designed for fastening rafters without cuts. They have higher shelves and are screwed on with a large number of screws. They are made from metal 2 thick; 2.5 or 3 mm.
| Designation | Size (length height width, metal thickness) in mm | Designation | Size (length height width, metal thickness) in mm |
|---|---|---|---|
| Reinforced corner | 105 × 105 × 90 × 2 | Reinforced corner KP5 | 140 × 140 × 65 × 2.5 |
| Reinforced corner | 130 × 130 × 100 × 2 | Reinforced corner KP6 | 105 × 172 × 90 × 3.0 |
| Reinforced corner | 105 × 105 × 90 × 2 | Reinforced corner KP7 | 145 × 145 × 90 × 2.5 |
| Reinforced corner | 50 × 50 × 35 × 2 | Reinforced corner KP8 | 145 × 70 × 90 × 2.5 |
| Reinforced corner | 70 × 70 × 55 × 2 | Reinforced corner KPL1 | 90 × 90 × 65 × 2 |
| Reinforced corner | 90 × 90 × 40 × 2 | Reinforced corner KPL11 | 90 × 90 × 65 × 2 |
| Reinforced corner KP1 | 90 × 90 × 65 × 2.5 | Reinforced corner KPL2 | 105 × 105 × 90 × 2 |
| Reinforced corner KP11 | 90 × 90 × 65 × 2.5 | Reinforced corner KPL21 | 105 × 105 × 90 × 2 |
| Reinforced corner KP2 | 105 × 105 × 90 × 2.5 | Reinforced corner KPL3 | 90 × 50 × 55 × 2 |
| Reinforced corner KP21 | 105 × 105 × 90 × 2.5 | Reinforced corner KPL4 | 70 × 70 × 55 × 2 |
| Reinforced corner KP3 | 90 × 50 × 55 × 2.5 | Reinforced corner KPL5 | 50 × 50 × 35 × 2 |
| Reinforced corner KP4 | 70 × 70 × 55 × 2.5 | Reinforced corner KPL6 | 60 × 60 × 45 × 2 |
A few additional words need to be said about some of the corners shown in the table, since their description requires clarification:
— KR 11 and KR21 are improved corners, often marked as TO P1 and KR2. These elements have an oval-shaped anchoring hole, which reduces the risk of bolt breakage in the event of structure shrinkage.
- КР5 and КР6 are corners used for fastening elements on which a large bearing load falls. Corner TO P6 is also equipped with an oval hole, and it is recommended to use it when creating a rafter system on a new house, which will still shrink. These models are in demand when installing structures that have a lot of weight.
— Corner TO M is made of perforated steel and is used for fastening rafters with a large section. It is especially suitable for wooden buildings. This corner fixes the structural elements very securely, and when using it, it is not necessary to cut the rafters into the Mauerlat - it is enough to cut the correct angle at the first.
- The KMRP corner is used to fasten parts of the truss system at right angles, including rafters with Mauerlat. It also differs from conventional angles in that it has an elongated hole, which allows displacement during shrinkage without damaging the fixing bolt. It can be used in a design where it is impossible to cut one element to another.
KMRP corners are produced from steel 2 mm thick. Three varieties are available:
| Angle designation | Dimensions in mm | ||
|---|---|---|---|
| a | b | c | |
| KMRP1 | 60 | 60 | 60 |
| KMRP2 | 80 | 80 | 80 |
| KMRP3 | 100 | 100 | 100 |
- Another option for fixing the rafters on the Mauerlat is to install them between two boards, sawn at a certain angle, and additionally fixed at the bottom with metal corners or LK mounts.
This fastening gives good rigidity and reliability. This method is well suited in cases where the rafter needs to be fixed at the right angle, lifting it above the horizontal plane of the Mauerlat, but fixing it to the vertical outer side.
- A method of attaching rafters to a Mauerlat made from a beam of not too large a section. It is carried out by reinforcing the bar with wooden linings having the required thickness.
Fastening using a reinforcing lining Sections of boards are attached to the mauerlat using nails or self-tapping screws in the places where the rafter legs will be installed.
In this case, cuts of the required configuration and depth are made in the rafters. The rafter legs are securely fixed to the wall using steel wire, which is secured to a driven steel crutch.
- In addition to the above-described fastening methods, the rafters are nailed to the Mauerlat using brackets. It should be noted that this method is quite common and has been used for a very long time. If these elements are properly secured, the rafter system will last for many years.
Fastening “the old fashioned way” - with staples The staples can be of different sizes and are driven in at different joints.
- Another fastening element that is used as an auxiliary element is perforated tape TM. It is used to strengthen the fastening unit if additional fixation is necessary.
In some cases, this element may be irreplaceable, so it also cannot be excluded when installing rafter legs on the mauerlat.
Features of rafter systems
It is selected depending on the location of the load-bearing walls of the building. Each of the systems has its own additional supporting or tightening elements.
Layered rafters
A system with layered rafters is distinguished by the fact that it has one or more support points, in addition to load-bearing walls. Due with this, with side walls, a significant part of the load is removed.
In the form of additional supporting elements, side posts and “headstocks” are used, supporting and secured to the floor beams. And the beams themselves, in turn, simultaneously serve as tension for the structure, and also lighten the load from the rafter system on the load-bearing walls.
Layered rafters are attached to the Mauerlat most often with sliding joints, which can move when the walls shrink or deform, leaving the roof structure intact. This is especially important to take into account in new buildings, since any newly built building necessarily shrinks under the influence of temperature fluctuations and ground movements.
Hanging rafters
The rafters are called hanging due to the fact that they have no other supports besides the two side load-bearing walls. It turns out that they seem to hang over the internal space of the building. In this case, the entire load from the roof frame structure falls on the Mauerlat.
To attach hanging rafters to the Mauerlat, rigid fastenings are used with no degree of freedom of movement, since the frame structure has only two points of support.
The hanging rafter system is braced and therefore puts a lot of pressure on the walls.
To remove part of the load from the walls of the building, additional elements are used, such as struts, headstocks and bolts, which pull the system to the ridge beam and evenly distribute the load on all walls. The crossbars are installed parallel to the floor beams and tighten the rafters together. Without these additional parts, the design may become unreliable.
Calculation of rafter installation
In order for the rafter system to be reliable and durable, in addition to the optimal connection method, you need to choose the correct spacing of the rafter legs. This parameter is selected depending on the size of the rafters (them and the length between the support points), as well as on the roof structure.
In this table you can obtain information about the necessary parameters for installing a reliable rafter system.
| Installation pitch of rafter legs in mm | Length of rafter legs in mm | ||||||
|---|---|---|---|---|---|---|---|
| 3000 | 3500 | 4000 | 4500 | 5000 | 5500 | 6000 | |
| 600 | 40×150 | 40×175 | 50×150 | 50×150 | 50×175 | 50×200 | 50×200 |
| 900 | 50×150 | 50×175 | 50×200 | 75×175 | 75×175 | 75×200 | 75×200 |
| 1100 | 75×125 | 75×150 | 75×175 | 75×175 | 75×200 | 75×200 | 100×200 |
| 1400 | 75×150 | 75×175 | 75×200 | 75×200 | 75×200 | 100×200 | 100×200 |
| 1750 | 100×150 | 75×200 | 75×200 | 100×200 | 100×200 | 100×250 | 100×250 |
| 2150 | 100×150 | 100×175 | 100×200 | 100×200 | 100×250 | 100×250 | - |
Use it in the article on our portal.
Prices for various types of fasteners for rafters
Rafter fasteners
Several rules for attaching rafters to the Mauerlat
In order for the fastenings to be reliable, it is necessary to follow a number of rules that are provided for this process:
- If metal connecting parts are used for fastening, then they must be fastened to the wooden connecting elements with maximum care - with high-quality self-tapping screws of the required length.
- If the rafters are to be laid in grooves in the mauerlat, then the dimensions must be precisely adjusted. This will ensure a tight, reliable installation of the rafters into the prepared cut, which should have a depth of ⅓ of the Mauerlat. However, it should be remembered that such a rule will only be valid if the Mauerlat is made of a powerful block with a cross-sectional size of at least 150 × 150 mm.
- In order not to weaken the Mauerlat, most often the cuts are made in the rafter leg itself at the desired angle, and in addition the knot is then fixed with corners. In this case, the cut should not exceed ¼ of the thickness of the rafters. This mount is rigid and can be used in a hanging rafter system.
- When using bolts to fasten rafters with slopes, puffs and other wooden elements, it is imperative to install a washer or a metal plate on the bolt in order to avoid flooding the nut into the wood and, accordingly, weakening the structure.
- Fastening rafters to the Mauerlat only with nails or self-tapping screws is considered unreliable. therefore, it is imperative to use corners or other metal fasteners of various configurations.
- When installing rafters on wooden walls, whether it is a hanging or layered system, it is recommended to attach them to the Mauerlat with a sliding fastening, especially if the roofing material is quite heavy.
Video: a few examples of attaching rafters to the Mauerlat
The roof structure will be strong and will last a long time, without being deformed by a variety of external influences, if the calculations of all elements are made correctly, and all fastening units are correctly selected and installed correctly.
Rafters are the load-bearing elements of the roof. Mauerlat, the basis of the rafter system, a kind of foundation for the roof structure. Proper fastening of the rafters to the mauerlat ensures the reliability of the entire structure, eliminates deformation of the rafter system, and prevents the roof from collapsing under the weight of an external load.
Mauerlat - correct installation
The Mauerlat, which is essentially the foundation of the roof, is made of logs or timber, laid around the perimeter, designed to ensure uniform load transfer roofing structure on the walls and foundation of the building. In order for the roof to stand firmly, the rafters must be properly fastened to the mauerlat.
Important! IN wooden house made of timber or logs, the upper frame of the walls, the upper crown, serves as the mauerlat; no additions to it are required. In a house made of brick, foam or aerated concrete blocks, or building stone, a mauerlat must be installed.
Brick or block walls do not react well to undistributed loads; the blocks or bricks themselves are a poor material for fixing rafter legs. Even the most reliable fasteners are not firmly fixed in such walls; under load they can be torn out, resulting in deformation of the rafter leg and the entire roof.
The Mauerlat should be firmly attached at the upper ends of the walls along the entire perimeter to an equipped reinforced concrete belt. Attaching timber to concrete can be very reliable if the correct fasteners are used. Installation is in progress. It consists of pins, studs, anchors, embedded in concrete on which they are then made.
Important! The ends of the fastening pins should be bent from below, the distance between them is 1-1.5 m, the diameter of the fastener should be at least 15 mm. In the timber that will be used as a mauerlat, make technological holes for fasteners and secure the top of the fastening with bolts. Before installing the Mauerlat, lay a layer of waterproofing material. 
After the base is installed, you can begin to work with the rafters.
Overview of fastener types
Fastening during any work related to the construction of a roof is a very important point. To attach strong and reliable rafters to the mauerlat, various metal fasteners are used, and also different geometries of inserts and cuts are used. For rafter fastening the following are used:
- wire;
- corner;
- plates;
- brackets;
- LK elements;
- nails;
- self-tapping screws.
And much more from perforated tape to studs. The use of one or another type of fastening requires different installation techniques.
If the rafters are fastened to the mauerlat using brackets, no cuts are required; if the LK fastening is used, anchors are not needed. The use of perforated tape makes the connection unit super-strong. Fastening with an angle is the most popular and in demand, since it does not need to be cut into the wood of the rafter leg; the angle is easily mounted with self-tapping screws. 
Important! You can't skimp on fasteners. It must be of high quality with an anti-corrosion top layer, galvanized. Fasteners that rust in a beam destroy it.
Principles of connecting rafter legs to the Mauerlat
The design features of the roof determine how the rafters are attached to the mauerlat. Spacer rafter structures, as well as those in which spacers are not used, rest on the Mauerlat. Slab and hanging rafters can rest on it; the connection can be rigid and sliding.
A rigid connection is such a connection between the rafter legs and the Mauerlat, in which shifts, displacements, and bends of the elements are impossible. The immobility of the connection is achieved by fastening using a corner. A saddle is cut out in the rafter leg, this reduces the strength, so it is additionally reinforced with brackets, tightened with bolts, and also the rafter attachment point is connected to the Mauerlat by twisting wire at the locations of the anchors embedded in the reinforced concrete support. 
A sliding fastening, a slide for rafters to the mauerlat, differs from a rigid fastening in that it allows some displacement of the rafter leg relative to the base, this avoids deformation and failure of the roof during shrinkage, snow and wind loads. 
Important! If during the installation process of attaching a rigid type of rafter leg to the mauerlat it is necessary to make a nest or notch, such elements should be made on the rafter, and not on the mauerlat. The foundation cannot be weakened.
Proper support of the rafter leg with the Mauerlat ensures the reliability of the roof and its durability. With any method of support, in order to fix the rafters on the mauerlat, it is important to observe three fundamental points:
- correct and precise making of cuts, cuts, etc., for a perfect fit of the elements;
- the use of washers, nuts, and groovers to prevent the fastener from sinking into the wood;
- It is unacceptable to use pads that can change shape over time, which will lead to load redistribution and destruction.
Correct installation of the roof support system guarantees its longevity.
Types of connection of rafters with Mauerlat
The rafter system consists of many elements, but the main ones are the rafters.
Important! How to attach the rafters to the mauerlat depends on what kind of rafters are used (sloping, hanging), on the loads and how massive the roof is.
The fastening can be sliding and rigid, closed and removable.
The most used connection of rafters with Mauerlat:
Installation of rafters on the Mauerlat is carried out using improved corners KR1, KR2. Their design provides technological holes for anchoring. The oval shape of the holes reduces the risk of tearing out anchor bolt when the wood base of the structure dries out. Also reliable are the corners KR5, KR6, which are needed to attach the rafters to the Mauerlat under heavy loads of a massive roof. It is better to securely fasten the rafters to the mauerlat, if they have a large cross-section, with perforated corners of the KM. This fastening is very reliable, no insertion is required, but an exact angle is required.
Important! For fastening at right angles, a reinforced KMRP corner is used; it differs from conventional corners by an elongated hole, it is used to compensate for roof displacement, it is made in such a way that during such processes no damage to the fastening elements occurs, it is especially suitable where it is impossible to insert one part into another. The corner is made of durable steel 2mm thick. 
Another type of connection is installation between boards. The boards are fastenings; they are cut at the desired angle and fixed at the bottom with corners.
Methods of fastening rafters using board linings, twisted wire, staples, to the Mauerlat are also used. These types of fastenings have been known for a long time, are popular and economical. 
Types of rafter supports on the Mauerlat
Mainly built for residential buildings gable roofs. Special attention with a gable structure, a node for supporting the rafters on the mauerlat is required. It is clear that a wooden base requires wooden beams.
Important! Rafters are required to be of the correct shape, without knots, calibrated and milled on all sides. The cross-section of the gable roof rafters is 40x150mm, the Mauerlat is 100x100mm.
The choice of fastening type depends on the geometry of the gable roof. You can fasten the rafters using all the methods listed above. It is also worth considering the hinged attachment points of the rafters to the Mauerlat.
A hinge joint is a type of connection that allows a beam to move in a circle. This happens with the help of one nail or self-tapping screw screwed into the Mauerlat. There is a node with one, two and three degrees of freedom. A unit with two degrees of freedom allows the beam to move horizontally; the rafters are secured with slides. With three degrees of mobility, the unit is installed using a slider, a special support for sliding the rafters in a vertical, horizontal position, in addition, the rafter can rotate in a circle. For this purpose, a special hinge is made, which is attached to the base.
Important! The most typical method for a gable roof is to use a zero-freedom assembly. The rafter is fastened with corners on both sides, remaining motionless.
The complex geometry of a gable roof requires the use of layered and hanging rafters. Beams supported on a base are effectively secured using perforated tape.
Layered rafters rest on the base and other support points, thereby relieving part of the load. Side posts can be adjacent to them, ridge headstocks, rafters tighten the structure, strengthening it. Layered structures do not rest on the base, but slide along it. Hanging rafters do not rest on the base; hanging over the interior of the roof, they are supported by the side load-bearing walls. 
Basic rules for pairing rafters with the Mauerlat
For a reliable connection, you need to carefully fasten the connecting elements and select them of the required sizes. It is necessary to accurately check the cuts, making them no more than a third of the size of the base. Use high-quality timber for the base of the correct section.
Important! You cannot use only nails and self-tapping screws for fastening; such fixation cannot be considered reliable; metal fasteners of various types should be used.
The roof will be strong and durable if the calculations are carried out correctly, the material is selected correctly and the joints are installed correctly.
The rafter system is the basis of the entire roof. And its long-term safe operation depends on how well it is designed, how the materials for it and fasteners are selected correctly. Therefore, this article will consider only one question, how to fasten the rafters. In this case, you need to understand the fastening of the rafters to the mauerlat, to each other, to the ridge beam and other elements of the roof structure.
To understand where the rafters usually join with other parts of the roof, you need to know that there are two different designs of rafter systems.
Fasteners
Modern market building materials today offers a wide range of fasteners for connecting rafters to each other and to other roof elements. Just recently there was no such diversity. The most commonly used were nails, studs with threaded connection and wire. It all worked, there were no complaints. But, as practice has shown, new fasteners for rafter systems have higher technical and operational characteristics.
Therefore, a short overview of modern fasteners.
Main types of connections
IN various designs rafter systems have different ways of installing them, and, accordingly, connecting them. But there are not many main junctions.
Connection with Mauerlat
It all depends on what kind of lumber the mauerlat was made from. For example, in a frame and stone house it is a beam with a section of 100x100 or 200x200 mm. In a wooden house, this is the top crown in the form of a log, that is, an element with a round cross-section. Therefore, each Mauerlat uses its own fasteners.
For example, the photo below shows a rigid mount. It provides a joint between the rafters and the mauerlat, which under any circumstances will withstand torsional, turning, sliding and other loads. Usually, for this purpose, a notch is made on the rafter leg, called a saddle. Most often, such structures are used when rafters are attached to the floor beams and the mauerlat at the same time.
Note! For reliability, the fastening is reinforced with nails, a threaded rod, and metal tape. This is actually a strong connection.
And a few more points.
- For fastening, three nails are usually used: two are driven from different sides of the rafter leg at an angle, the third into the upper end of the rafter exactly vertically.
- It is prohibited to make cuts on the Mauerlat; this reduces the load-bearing capacity of the element due to loss of integrity.
- The saddle is made according to a template.
There is a so-called sliding method of fastening. For this purpose, sleds are used. The photo below clearly shows how the fasteners are installed and attached to the rafters and logs. This option, as mentioned above, is used during construction wooden houses, which shrink within two or three years. And this can lead to deformation of the roof structure, and sometimes to its collapse. The sliding support for the rafters makes it possible to avoid troubles.
Attaching to beams
Not all rafter structures are attached to the Mauerlat. If the floor of the house is made of load-bearing beams, then the rafter legs are attached to them. In this case, it is necessary to understand the fact that the loads will act pointwise, and not along the entire plane of the walls being erected. In addition, this design is a 30-40 cm protrusion outside the house, which already complicates the fastening process.
In this case, it is very important to accurately align the rafters themselves at one specific angle. Therefore, first, put two legs on different sides of the building in the same plane with the same angle. After which a thread is stretched between them, which will serve as a level. All other elements are set according to it.
Rafters are usually attached to beams with nails or metal fasteners. Most often this is a perforated plate or tape. The photo below clearly shows how all elements of the roofing system are installed and how they are attached to each other.
Skate attachment
There are three schemes by which the connection is made.
- The rafters are installed end-to-end with trimming according to the template to form the required connection angle that forms the angle of the roof slope. The rafters rest on the ridge beam, and they are fastened with nails at the upper ends, and additionally with perforated plates.
- The same thing, only without the ridge beam.
- The connection is made with an overlap, where the fastening is carried out with a pin, which passes through the through holes of the two rafter legs. In this case, nails are additionally used. Typically this method is used on hanging rafters without laying them on a ridge beam. It is better in reliability than the second option, because it has a larger contact area between the two elements.
And in this unit you can use sliding supports for the rafters. Essentially, these are two pairs of perforated plates that are secured together with pins. There are three studs: two connect the plates through the rafter legs, one in the space between the rafters. This is clearly visible in the photo below. This design allows the rafters to move, changing their angle, without affecting the strength of the entire system. That is, the angle between the elements can change.
Extension of rafter legs
It often happens that the length of one leg is not enough to cover the roof. Therefore we have to lengthen it. In this case, the requirement must be met - the strength of the element is not reduced.
There are also three options:
- Two boards are cut at the joint at an angle of 45° and fastened together through a through hole with a bolt with a diameter of at least 12 mm.
- The connection is made end-to-end, with the junction on both sides covered with boards with overlays made of the same material as the rafter legs themselves.
- Overlapping. It is necessary to maintain an overlap length of at least 1 m. Fasteners are installed in a checkerboard pattern.
Everyone chooses for themselves the option of connecting rafters that will correspond to certain design parameters and operating conditions of the house. This includes what material the structure is being built from, the shape of the roof, the type roofing material(heavy or light), climatic conditions of the area where the house is being built. But there are certain rules that must be followed.
- Don't skimp on fasteners. You need to choose the best and most modern ones. It's best to use a combination of several options.
- Reliable fastenings are metal shaped products, as well as studs and bolts. Nails and screws can be used for temporary fastening.
- During construction wooden house Sliding fasteners should always be used.
- If you use the installation of rafters with cuts, then this must be done very carefully. The best option– use templates for this.
- If bolts or studs with nuts are chosen to fasten the rafter legs, be sure to install large diameter washers between them. They are the ones who create a tight fit, and they are the ones who will hold the load when pressed.
The Mauerlat is considered an important element of the roof structure, since the roof actually rests on the support beam. It helps to distribute it evenly and rationally on the roof. The rafters are also attached to it.
Attaching the rafters to the mauerlat is a significant step in the construction of the roof. The strength and safety of the roof depends largely on the quality of installation of the rafter system, in particular on the right choice fastening elements and proper connection of the supporting structure units.
Attachment points for rafters to the Mauerlat
There are two ways to attach rafters to the Mauerlat:
- hard and
- sliding.
Obviously, the technology for attaching the rafter leg to the support beam will determine its “behavior” in various weather conditions. For example, when there are temperature changes or snowfalls, the supporting structure cannot be static. Indeed, under conditions of high humidity, wood expands, and high temperature causes compression. If you use rigid fixation, there is a risk of displacement; even ruptures cannot be ruled out. Due to improper installation, a thrust force may appear, which poses a danger to the walls. Therefore, proper fastening of the rafters to the mauerlat is a certain guarantee of safety.
The following support units are distinguished:
- articulated
- one degree of freedom. Allows a beam made of wood or metal to rotate in a circle. This state can be achieved by using one screwed-in nail or self-tapping screw for fixation;
- two degrees of freedom. Rotation of the beams in a circle or slight movement in the horizontal plane is allowed. It is achieved by fastening the rafters either using a slide or using a sliding support - a slider made from mounting angles;
- three degrees of freedom. The rafters can be moved in a circle, as well as in vertical and horizontal planes. A similar effect is obtained due to a specially made hinge, which is screwed into the murlat;
- zero degree of freedom. The ends of the beam are rigidly fixed at both ends, which prevents it from moving. This option is mainly used in brick buildings.
Rafter leg mounting options
To perform the lower assembly of supporting the rafter leg on the support beam, one of the following methods is generally chosen:
- sliding, which is a movable connection: the lower end of the beam is held on the mauerlat only with the help of fasteners that do not prevent it from sliding along the beam;
- spacer is a fixed coupling unit with a rigid support of the rafters in the timber.
Both of these options have the same right to life and are used taking into account the shape of the roof and the features of the rafter system.
Fastening methods with and without sawing
Let us immediately note that fastening the rafters to the mauerlat without cutting is used exclusively in the case of a sliding connection. To hold the lower edge of the rafter legs freely lying on the mauerlat, corners are usually used. Obviously, such a fixation may not withstand significant loads, so it is recommended to use it primarily when covering relatively small spans.
The device of the lower interface unit, which uses fasteners with a notch that locks the tooth, is considered much more reliable. It is cut into the rafter board. As a rule, it occupies no more than a quarter of the beam. You can do it in different ways:
- rigid fixation, which works on compression formed by the emphasis directed towards the inner side of the support beam;
- movable fixation formed by the tooth on the outside. To prevent the rafter legs from slipping off the murlat, they are fixed with fasteners that work in tension, for example, staples or corners.
- The cut in the rafter beam is sometimes replaced by a board that is nailed to the rafter leg.
Fasteners for rafters and rules for working with them
The modern construction market offers a wide range of fastening elements. Apart from classic options– staples, twisted nails or rolled wire, which is folded in several rows, here you can find special kits designed for working with rafters.
Attention!
In the process of connecting wooden parts with screws (bolts), metal washers must be used underneath them. This simple technique will help avoid fasteners from sinking into the wood.
Fastening work is carried out in a certain order. We present to your attention some of the most simple methods sawing and subsequent adjustment of rafters.
The rafter legs are fixed with one of the fastening options. It should be noted that each of them has its own subtleties. The choice is based on parameters such as the angle of inclination of the slopes and the optimal support unit.
- The nails are driven into the support beam through the rafter board at an angle. For a proper connection, you need to use two nails nailed on both sides towards each other. In other words, the nails cross inside the murlat. The fastening is completed by another nail driven vertically.
- One end of the staple is driven approximately into the center of the support beam from its inner side. The other - into the rafter, turning it at a right angle.
- Wire rod folded in four rows is used to make a clamp. With its help, the rafter leg is screwed to the beam in the direction from the outside to the inside. The wire can be replaced with a special perforated tape. Often, a tie with a wire or staple is used as a backup fastening in addition to other types of connections.
- The corners are screwed with screws on both sides to the rafters and rafters and to the upper edge of the murlat. The connection will be more reliable if you use corners that have two rows of holes and a stiffener.