Prefabricated strip foundations made of FBS blocks. Making a foundation from FBS blocks. What is FBS

The use of FBS blocks allows you to build a solid foundation for various structures. The construction budget for a monolithic structure and a foundation made of FBS is almost the same, but the speed of construction of the latter is incomparably higher. Industrial production of block material ensures durability and reliability of single-story and multi-story buildings. Step-by-step instructions will help you independently master the construction of a foundation from FBS blocks.

Characteristics of foundation blocks

The production of reinforced concrete products is regulated by Gosstandart, which stipulates the characteristics of the material, dimensions, conditions of transportation, storage and installation. Depending on the type of structure, there are the following types of blocks:

FBP is distinguished by voids that are open downwards. This allows you to reduce the structural loads of the foundation on the soil.
The FBV has a cutout for laying communication systems and installing jumpers.
The main element of construction is a solid FBS wall block, characterized by increased strength.

Basic specifications materials are given in the table:

Reinforced concrete products are equipped with a mounting loop, which provides ease of foundation construction. It protrudes above the top edge and is pressed after installation or immediately recessed inside the block. The main dimensions of the material are shown in the table:

Features of the construction of a block base

The FBS foundation is quite simple to install. Initially, a reinforced cushion is prepared, then the walls are laid, and the work is completed with waterproofing.

Comment! If necessary, the design is supplemented with an upper armored belt.

An obstacle to the application of the proposed technology may be the lack of lifting equipment. It is possible to replace the crane with a winch, but this practice is impractical due to the significant increase in labor costs. Otherwise, the arrangement process does not pose any problems even for beginners.

In terms of strength and rigidity, a foundation made of FBS blocks is inferior to its monolithic counterparts. Its advantageous aspects are simplicity and speed of construction, lower costs. The block base is optimally suited for sandy soils. If there is soft and crumbly soil, it is better to abandon this idea due to the risk of subsidence of the structure. This can provoke deformation or destruction of the erected structure.

The foundation of a house made of FBS blocks will withstand soil heaving with virtually no consequences. Under similar impacts, a monolithic structure can rupture, and the block element will only bend. The reason for flexibility and mobility is the presence of seams.

Another advantage of FBS products is the ability to build a foundation in any weather conditions. Snow or rain are not an obstacle to the installation process. It is impossible to pour a monolithic structure under such circumstances.

Preparatory stage

A foundation made of FBS blocks requires a preliminary design. An excellent assistant will be a computer program, in the absence of PC skills, the masonry is drawn on paper manually. A detailed description will help to take into account all the nuances of installation and tying the FBS foundation. When drawing up a project, the type of soil, level groundwater, number of storeys of the structure and total loads.

Comment! If there are FL foundation slabs in the plan, it is easier to prepare a foundation pit. If FBS blocks are installed directly on the ground, a trench along the perimeter of the building will be sufficient.

The width of the trench exceeds the size of the block foundation by 1 m. This gap will be required for waterproofing, wall insulation, and drainage pipes.
The first row of FBS supports is maintained within 40 cm.
The next two rows are reduced to 30 cm.

By comparing the dimensions of the foundation and the FBS blocks themselves, determine required amount, after which they move on to purchasing materials. The project must take into account the outlet points for utilities to purchase blocks of the appropriate configuration. If you miss this point at the planning stage, you will have to drill holes in the foundation in the future, which will entail additional costs of time, energy and finances.

Excavation

Before you start building the foundation for a house, you need to look around the construction site. The location of the crane is determined in such a way as to reduce interference during operation to a minimum.

The installation of a FBS foundation is carried out in the standard sequence:

The corners of the future foundation made of blocks are determined, and pegs are driven in at this place.
A rope is stretched between the base marks.
Intermediate elements are installed at the points of arrangement of internal partitions and external walls.
A pit is being dug for FBS blocks. Its depth exceeds the level of soil freezing by 25 cm. The average value of the foundation made of FBS is 0.8-1.0 m. For large indicators, the arrangement of such a structure from blocks is impractical.

Advice! It is recommended to clear the remaining space of the site from a fertile layer of soil 10-20 cm thick.

Forming the sole

There are two ways to make a foundation from blocks. It’s easier to go with the sand cushion option. If the ground is unstable, a concrete support is chosen, but this significantly increases time, money and labor costs. Before the stage of forming a compacted sand cushion, the manual for constructing a structure from FBS contains the same points. The process of constructing a foundation on a concrete base starts with the installation of formwork and the installation of a reinforcement cage.

For work you will need sand, crushed stone of 20-40 fractions and reinforcement. Main stages of arrangement:

The bottom and side surfaces of the pit are leveled.
The pit for the FBS foundation is covered with a layer of sand 10-15 cm thick. The surface is saturated with water and thoroughly compacted.
A layer of crushed stone 10 cm thick is placed on top of the sand cushion and compacted again.

After this, they move on to the next stage of foundation construction using FBS blocks.

Arrangement of formwork, reinforcement

Edged board is the optimal solution for installing formwork under a foundation made of FBS blocks. The boards are fixed together in a convenient way; usually self-tapping screws are used for these purposes. The formwork is installed along the walls of the pit, maintaining the vertical position using a level.

The concrete support for the FBS blocks contains a reinforcement cage. It's easy to install:

For installation, take steel rods with a diameter of 14 mm.
The mesh is knitted, the cell sizes are chosen arbitrarily. Depending on the load on the block foundation, they choose the 10x10 or 15x15 cm option.
Reinforcement is usually done in two layers, with the upper and lower mesh spaced at the same distance from the crushed stone and the top of the future concrete support.
The mesh is fixed using pre-driven vertical reinforcement rods.

Comment! If FBS blocks are subject to significant load due to a massive structure, the number of reinforcing layers under the foundation can be increased.

Filling the pillow

The prepared structure is filled with concrete mortar. The process is carried out slowly to ensure an even layer. The reinforcement used to penetrate the fill at certain intervals will help remove air bubbles. The surface of the cushion under the block foundation is carefully leveled.

To gain strength, the concrete support is left for 20-30 days. At high air temperatures, the surface under the FBS blocks is periodically moistened with water to avoid the appearance of cracks.

Installation of blocks

FBS blocks are laid using a crane. After lifting the reinforced concrete products, a team of workers directs the blocks to the places provided for by the foundation design and straightens them. Fixation with each other is carried out with a solution using concrete grade M100. The average mixture consumption for fixing one FBS block is 10-15 liters.

Initially, the foundation blocks are placed in the corners. A thread stretched between them will help to better navigate during further installation of intermediate elements. The solution is poured and vertical seams foundation.

The need for waterproofing

Liquid mastic is optimally suited for waterproofing FBS foundations. To do this, the outer and inner side surfaces of the supporting structure are carefully treated with an insulating composition.

Advice! If the climatic zone is characterized by a large amount of precipitation, it is recommended to use roofing felt as an additional waterproofing layer.

Installation of armored belt

A foundation built from FBS material often needs an armored belt to increase its strength. To do this, a reinforced concrete belt 20-30 cm thick is cast along the top row of blocks. Steel rods 10 mm thick are used as reinforcement. During subsequent construction, it is on this base that the floor slabs are installed.

Some professionals dispute the need to erect a reinforcing belt; this is done at the discretion of the owner of the structure. But the quality of construction only benefits from such a measure.

The construction of the block foundation is completed here. Labor-intensive technology pays off with reliable results.

Solid foundation blocks (FBS) are a reinforced concrete material that represents part of the base that distributes the load. The blocks allow for quick installation and are not influenced by the external environment, in comparison with a monolithic base. FBS are distinguished by: strength, wear resistance, long-term operation.

Types of FBS for foundations, GOST

There are 12 standard sizes of classic FSB on the market:

The length of the blocks is 9/12/24 dm.
Width -3/4/5/6 dm.
The height of all blocks is 6 dm.

The production of blocks is regulated by GOST, which specifies the type of material, dimensions, design parameters, rules for storage, transportation, and installation.

FBS - solid block of maximum strength;
FBP - voids are located at the bottom, due to this the load on the foundation is reduced;
FBV is a solid texture with a cutout for laying communication systems. Relevant for the construction of facilities with numerous engineering systems.

Advantages and disadvantages of a foundation made of FBS blocks

The advantages include:

Saving time. No need to mix concrete, count the quantity consumables, maintain ideal proportions. FBS installation is carried out quickly and there is no need to worry about the quality of the foundation.
The manufacturer has provided for all aspects of block installation. Large blocks are equipped with special hooks for easy installation. Products are easier to place in the pit during construction multi-storey buildings or technically complex objects.
FSBs are equipped with grooves, which further strengthen the foundation.
If construction is carried out on unprepared soil or in northern regions,FBS easily copes with these problems. Chemicals are added to the material to increase resistance to deformation.

Disadvantages when using FBS blocks:

Price.
Use of special equipment for installation.
Great risk of foundation subsidence.

The disadvantages of the material include additional waterproofing and insulation, but today it is difficult to do without this stage.

Step-by-step installation of a FBS foundation

To lay the foundation blocks, a trench is dug. At this stage, it is important to consider the size of the FBS. The rock is cleared from the bottom, irregularities are eliminated, and the bottom is covered with sand. With a sandy bottom, doing this work is pointless.

Taken into account: soil type, total load, presence of groundwater, building height. If the project includes FL slabs, it is more rational to dig a foundation pit. If the FSB is installed in the ground, perimeter trenches are dug. Their width should be one meter larger for waterproofing, insulation and drainage.

Calculation of the number of FBS blocks

Initially, the height of the building is determined. The average depth of rock freezing affects the depth of the base.

Soil and subsoil often contain clay. Groundwater flows there, which expands in winter after freezing. If the foundation is not deep enough, the ice on the ground will push it out. In summer, with variable shrinkage of the rock, the foundation tape may crack: the building will become unsuitable for use. The amount of soil freezing is prescribed in the joint venture “Construction Climatology”. The minimum depth for laying the FBS base is selected with a slight increase in this number - by 200-300 mm.

Soil with sand is of the low-heaving type: water does not concentrate in the sand, freezing affects the stability of the foundation. However, groundwater washes away sand.

It is permissible to add a bedding of sand and gravel, then fill it with a 10 cm layer of concrete. Such a ball performs two functions:

drainage;
soil compaction.

The blocks under the foundation are installed with a solid strip, and the voids are filled. The dimensions of the FBS are not always equal to the perimeter of the structure. It is important to choose a configuration with the blocks fitting as tightly as possible. More than two types of materials are used: the main ones are mixed with additional ones - stand-out ones of reduced size. Brick is used to fill small voids, lay a leveling layer, and build a basement. The number of blocks is calculated before the start construction work. To do this, use special online calculators, or use the help of specialists.

Preparing and marking the area for the foundation

It is impossible to build a multi-storey building without proper design; all step-by-step stages, costs, markings are prescribed in the plan. After planning, markings are drawn:

The stake is driven in a meter from the corner. This will prevent the soil underneath from crumbling during construction work.
The cord is stretched across the entire working area, taking into account the basement and the width of the blocks.

When constructing buildings with a complex configuration, additional markings are made. Lime, paint, chalk are used.

Excavation

A well-built house requires professional design based on the results of engineering and geological examinations. Only in this case is it possible to avoid extraneous communications that approach the site. The composition of the soil and the presence of underwater currents are being studied. This will ensure the construction of a stable structure.

The foundation pit is dug:

when a basement or basement is planned;
when laying FL slabs;
with unsuitable soil composition.

In all other cases, they make do with trenches. The depth of the tapes is always calculated individually.

Drainage layer and pillow under the foundation

To ensure reliable fastening of concrete slabs, the load is distributed to the lower soil balls, which are replaced by non-metallic rock. Minimal crushed stone (5-10 mm) and sand are used, each layer is compacted using a vibrating plate or a manual tamper.

Laying a concrete cushion in low-rise buildings is done in rare cases (for example, for the construction of a three-story building). The quality of FBS is many times higher than the base of a monolithic structure due to maximum compliance with technology.

To proceed to installing the foundation, it is necessary to take into account the technique of laying blocks. Installation is preceded by marking. According to the drawings, stakes are inserted along which the thread is pulled. To facilitate the laying of the first row, blocks are placed in corners and intersections. The vertical seams are filled with building mixture or compacted deep. The resulting space is filled with concrete and leveled until a monolithic structure is formed between them.

The layer of construction mixture between two rows should be 5 cm. The seams are treated with a layer of concrete 2.5-6 cm. To strengthen the ligation between the rows, reinforcement is used. At the installation stage, it is important to make holes for the pipes of the sewer system.

The construction technology is carried out as follows:

setting corners;
installation of blocks;
filling voids;
laying bricks.

The installation takes place along a T-shaped crossing. The construction mixture is poured or spread with a shovel. Vertical joints are filled after installing a new row of blocks. The masonry is covered with plaster or building mixtures.

Technological openings include openings for doors. More often they are wider than the project plans to align the side surfaces brickwork. To increase the stability and durability of the foundation, the first FBS ball is widened.

Armopoyas

The reinforcement belt is important for the foundation. It is represented by a monolithic reinforced concrete ribbon closed at the edges, running along the perimeter of the house. All modern facilities cannot do without an armored belt; it is used on difficult or acidic soils. Is used for:

uniform vertical distribution of load coming from load-bearing walls;
prevention of unplanned shrinkage, which contributes to the formation of cracks on the walls;
compensation for point loads resulting from wall misalignment during operation of the house;
eliminating inaccuracies during construction or miscalculations at the design stage.

The armored belt implements a unloading function, which has a positive effect on resistance to possible damage.

The feasibility of its use increases:

when construction is carried out near reservoirs or underwater waters, ravines or on rock;
during seismic activity;
with a shallow foundation for the house.

Waterproofing

Isolation of the foundation from underwater water is carried out in several ways.

Vertically. The method doubles the percentage of stability and durability of the foundation. Injection involves filling voids and seams using a construction injection composition. The method requires expensive equipment and materials, but it will pay off in reliability and durability.

The work includes the following stages:

The seams of the blocks are embroidered at a depth of 3-5 cm.
A hole is drilled 2/3 of the wall thickness.
Parkers used for injection are installed.
A modified polymer is poured between the blocks. A pump designed to perform injection is used.
Then the parkers are dismantled.
The seams are sealed.
Coating waterproofing of load-bearing walls is carried out.

The feasibility of other technologies depends on the use of waterproofing materials:

Sizing - bitumen mastic in several layers.
Coating - bitumen mastic in one layer.
Painting - composite compositions of polyurethane, silicone, acrylic.
Plaster - cement mixed with polymers.
Changing the composition of the building mixture - the interpenetrating insulation of Penetron reacts with crushed stone at the molecular level, the entire block becomes water-repellent.
Dust - FBS foundation covered with liquid rubber dust.

It is more affordable to use painting and coating. The most disadvantageous is spraying.

The main factor in insulating from moisture is the integrity of the layer. This is easiest to achieve using any method other than sizing. Not only the blocks are processed, but also all walls, including the foundation of the basement.

Thermal insulation

FBS blocks are the basis for a basement or basement. In this case, it is important to take care of eliminating condensation. Thermal insulation technology looks like this:

the outer surface of the blocks is covered with synthetic heat-insulating material over the waterproofing layer;
a material prepared from chemical fibers is laid, which protects the heat insulator from unplanned deformations.

If the foundation is insulated from the outside, the formation of condensation on the walls of the basement is 100% eliminated. Internal insulation will lead to the opposite result.

If the project involves shallow strip foundation, the order of thermal insulation changes:

the outer surfaces of the blocks are covered with gas-filled material, the trenches are widened by a meter;
Balls of gas-filled material are laid out around the perimeter.

Drainage system

If there is a high percentage of groundwater, at the construction stage it is better to divert it from the foundation of the house while digging a pit. To do this, perforation pipes are laid along the boundary of the foundation. The general slope of the ring is carried out in the direction of groundwater, which will flow out by gravity.

To completely eliminate underwater or capillary water, it is enough to lay a layer of crushed stone. To stabilize the soil border, geotextiles are used, which prevents mixing of soil and crushed stone.

In the basement the slabs are poured building material at the level of the base of the foundation, additionally covered with slabs or beams.

Thanks to the optimal combination of its performance qualities, it has maintained a leading position for hundreds of years.

All alternative options supporting structures were created for specific conditions and are significantly inferior to tape in many respects.

The most rigid and durable types of tape are monolithic concrete castings, but they require a lot of time for the concrete to cure until it reaches technological hardness.

In addition, pouring a large base at once is extremely difficult, and interruptions significantly reduce the strength of the material.

Taking into account seasonality concrete works, the technology for installing prefabricated belts from durable reinforced concrete foundation blocks was developed, allowing work at any time of the year.

The abbreviation FBS stands for “foundation blocks of solid section”. They are reinforced concrete briquettes of different sizes, from which, like bricks, a strip foundation of any size is assembled.

It is allowed to use only standard products manufactured at the factory in compliance with special technology in accordance with the requirements of GOST and technical standards. Externally, FBS is concrete block, rectangular in cross-section and the floor of the side surface.

The end side has a small rectangular recess for pouring mortar or using it as a socket when installing vertical elements. The upper plane has a pair of loops for engagement with lifting equipment during installation.

After the block is laid, they are bent and pressed tightly to the plane. When assembled, the result is a canvas made of tightly packed blocks; vertical joints are placed at random to ensure greater strength.

The elements are connected to each other using sand-cement mortar.

What requirements must they meet for a strip foundation?

Foundation blocks are produced in accordance with technical specifications and GOST standards.

Based on their shape, the blocks are divided into:

Whole. They are basic briquettes with standard sizes.
Additional ones. Used to fill areas of the tape where a whole block cannot be placed.

There are two height options:

380 mm.
580 mm.

In practice, their values are rounded and called 30 and 60 cm, respectively.

Width:

300 mm.
400 mm.
500 mm.
600 mm.

The length of the blocks is:

880 mm.
1180 mm.
2380 mm.

In addition to sizes, FBS blocks differ in material:

Expanded clay concrete or silicate concrete with a minimum density of 1800 kg/m3.
High-strength lightweight concrete B100.
High-strength heavy concrete grades M200-M500.

The material also contains plasticizers that reduce the brittleness of concrete, and reinforcement made of high-strength steel A1 or A111. There are additives that increase the frost resistance of concrete.

NOTE!

There is another type of foundation blocks - small-format briquettes with dimensions 40:20:20 cm (length:width:height). It allows you to work without the participation of lifting equipment, but due to the large number of joints it is not able to form a tape of sufficient rigidity and strength, so it is used less often.

Advantages and disadvantages

The advantages of FBS blocks include::

Strength, high load-bearing capacity.
High quality material obtained in modern technological conditions.
The design of the blocks ensures optimal installation density, making the tape durable and resistant to external influences.
The design of the elements is universal and allows the creation of foundations of any configuration.
Work can be carried out at any time of the year, which significantly expands the possibilities compared to concrete casting.
The time required to create a tape is significantly reduced compared to monolithic base construction options due to the lack of a long curing period for concrete.

Disadvantages of prefabricated foundations made of FBS:

The work cannot be done manually. Due to the heavy weight of the blocks, lifting equipment is required.
Joint seams are problem areas regarding the strength and tightness of the tape.
The heat-saving qualities of the blocks are relatively low.
The price of such a foundation is noticeably higher than that of a monolithic type.

The main advantage that determines the popularity and wide distribution of their FBS tapes is the high speed of installation and the absence of seasonal dependence on climatic conditions.

Burying depth

It has a width equal to the design parameters of the sole, and the height of the shields is assumed to be slightly increased compared to the height of the cushion itself.

The panels are assembled from edged boards The shields installed inside the trench rest against the side walls of the trench. A layer of geotextile is laid on the bottom to prevent water from escaping from the concrete.

Reinforcement

The installation of a reinforcement cage is necessary to compensate for tensile loads that occur during movement or heaving of the soil. Metal or composite reinforcement bound with soft steel wire is used.

The dimensions and configuration of the arm belt correspond to the design parameters of the sole and are designed so that the working rods are no deeper than 2-5 cm under the outer layers of concrete.

The thickness of the working rods depends on the size of the sole and is usually in the range of 10-14 mm.

Filling the pillow

Concrete must be supplied from different points so as not to wait for it to spread on its own along the entire length of the trench. During pouring, bayoneting or processing with a construction vibrating plate is performed to remove air bubbles.

Concrete grades M100 or M150 are used; if necessary, the heavier type M200 can be used.

must be done at one time until the concrete begins to set. This is important, since solidity is ensured only in this way; if you take breaks in pouring, then the whole procedure becomes meaningless.

Installation of blocks

Installation of blocks begins only after the concrete pad has been completely cured (28 days). During this period, the material gains structural strength and is capable of bearing the load from the weight of the FBS.

The blocks are laid on a layer of sand-cement mortar, which is applied to both horizontal and vertical joints. The blocks are laid with offset vertical joints. To fill the rows, short (additional) blocks cut to length are used.

Cutting is done using specialized diamond cutting tools.

Waterproofing

The surface of the finished tape is covered with a layer that prevents water from penetrating into the concrete.

Hot tar, ready-made bitumen mastic or other materials are used as an insulator..

All surfaces must be insulated, including the internal parts of the ventilation openings.

Insulation

Insulation is the process of installing a heat insulating tape on the surface. Optimal choice extruded polystyrene foam (penoplex) will become, somewhat worse - polystyrene foam. They are impermeable to water and do not rot, which is important for difficult operating conditions.

It is possible to use liquid polyurethane foam, a more expensive but very effective insulation with maximum tightness. The material is installed tightly, without cracks or gaps, on the surface of the tape from the inside and outside.

Any gaps found must be immediately filled with foam..

Useful video

In this video you will learn how to make a strip foundation from FBS blocks:

Conclusion

The construction of a strip foundation from FBS blocks can significantly speed up work and remove restrictions on climatic indicators. The resulting foundation is demanding in terms of soil composition, but in favorable conditions it demonstrates high efficiency and reliability.

The main advantage is saving time, which is important when building large houses.

The cost of purchasing blocks is higher than purchasing concrete, but this difference is not too noticeable and is compensated by an improvement in the construction schedule.

In contact with

Prefabricated foundations are quite a rarity in domestic individual housing construction. However, such a foundation system is not without its advantages. Today we will analyze the construction of FBS foundations, the benefits of using this technology and possible pitfalls that await an inexperienced developer.

Organization of work execution

Prefabricated concrete foundations are used where monolithic construction is impossible or undesirable for a number of reasons: from the significant distance of the concrete unit and unfavorable climatic conditions to the developer’s simple unwillingness to deal with the complexities of constructing formwork, reinforcement and pouring heavily buried structures.

At the same time, a foundation made of FBS has a much higher construction speed with a significant reduction in labor costs. However, the technological complexity of constructing a prefabricated foundation for a house can be even higher than with monolithic concreting. It requires the involvement of earth-moving and loading equipment, careful calculation of the order of laying blocks and adherence to the order of construction work.

The general procedure for constructing a foundation from FBS is as follows:

Marking the site according to construction project and the binding scheme.
Excavation work: removing soil to the freezing depth, forming inclined walls of an open pit according to the calculated collapse prism.
Pouring a monolithic base, or installing a cushion or footing.
Laying the blocks in order, bandaging them with cement mortar and reinforcing mesh at the corners and junctions.
Holding the foundation until shrinkage is complete.
Filling of the reinforced seismic belt and installation of the first floor.
Construction of the walls of the first floor.
Installation of waterproofing and insulation of the foundation.
Backfilling of soil.

The composition and order of work may differ slightly. In particular, when the groundwater level is high, artificial drainage of the construction site can be carried out, but, depending on the hydrogeology of the site, a drainage system can be laid both at the initial stage and immediately before backfilling. However, after studying the features of the construction of prefabricated block foundations, most questions about the technology and stages of their construction will disappear by themselves.

Load-bearing qualities and stability of the foundation

The lack of solidity of prefabricated foundations significantly reduces their structural strength. The main destructive effect comes from lateral deformations of the soil and frost heaving forces. Despite the fact that block foundations perfectly withstand compressive loads, their resistance to displacement is very low if the base does not experience a sufficiently high degree of compression from those located above building structures. In turn, the absence of a common reinforcement frame makes the prefabricated foundation very susceptible to bending and twisting influences.

Two main rules in the construction of prefabricated foundations:

Their location is entirely in the freezing layer of soil or below the freezing depth, which prevents the structure from being lifted by frost heaving forces.
Elimination of lateral impact from the ground until the moment when the compressive effect is high enough so that the friction forces between the blocks prevent their displacement.

In this case, it is also necessary to level out the difference in the density of the soil layer on which the foundation rests. This is done by installing blocks on a monolithic reinforced concrete grillage strip or slab, which acts as a load distribution from the resistance of the soil.

Preferred soil types

Prefabricated foundations are not suitable for subsidence and highly heaving soils due to the low degree of resistance to bending loads. At the same time, one should not confuse cases when a load-bearing base is assembled from FBS and options for using blocks for the construction of basement walls. In the latter case, the supporting function is performed not by the blocks themselves, but by the NZLF tape or the monolithic slab underneath them.

The construction of a foundation from blocks using basic technology is shown for dry and hard-plastic underlying soils, the bearing capacity of which, in terms of the bearing area and the weight of the building, provides a reliability coefficient of the order of 1.2-1.4. In general, we can recommend laying a prefabricated foundation without a grillage with a bearing capacity of the soil of at least 4.5 kg/cm2.

Construction of a monolithic reinforced belt for laying FBS blocks

If the density of the underlying soil provides a bearing capacity of the order of 3.8-4 kg/cm 2 (sandy loam, fatty clays) or conversion to mass and bearing area does not guarantee a positive reliability coefficient, the foundation should be laid on top of a sand and gravel preparation with a trapezoidal profile. If the safety factor is less than 1, FBS can only be laid on a grillage or, at a minimum, on an expanded concrete base.

Types of foundation blocks

The FBS range is not particularly wide. According to GOST 13579-78, with a block height of 30 or 60 cm, their width can be from 30 to 60 cm in increments of 10 cm. The length of the blocks ranges from 90 to 240 cm, while the standard binder seam is already included in the length and height dimensions, that is, in reality the blocks are 20 mm shorter and lower.

By default, foundation blocks do not have reinforcement with the exception of embedded mounting loops. Concrete of strength class from B7.5 to B15 is used as the main material. At the same time, when making blocks to order using standard forms, there are no restrictions on placing linear or mesh reinforcement in concrete, or using a mixture with special parameters, for example, with increased frost resistance.

For the construction of concrete foundations and load-bearing basement walls foundation wall blocks (FBS) are used; in some cases they are made of heavy concrete. Varieties of blocks made of silicate or expanded clay concrete are unsuitable for load-bearing and critical structures. In turn, foundation blocks can be marked FBV (with a longitudinal groove) or FBP (with voids in the manner of a cinder block).

Combined device systems

So, in classic version The FBS foundation is designed incredibly simply and even primitively: a lower and upper reinforcing belt, between which there can be an arbitrary number of rows of blocks, but usually no more than 4-5. This type of foundation is optimal for buildings without a basement or technical subfloor, that is, the blocks are supported on all sides by soil, and their squeezing inward is excluded.

If there is a basement or ground floor, compressive loads along horizontal axes can be compensated in two ways:

Strengthening the seams with 8 mm reinforcing mesh, compensating for the internal tension zone.
Installation of internal lintel walls.

It is also possible to lay FBS on unstable soils, but, as already mentioned, only if there is a load distribution system - a pile-grillage or strip foundation. If desired, the cutouts of FBV slabs can be used for arranging prefabricated monolithic foundations. In this case, the cutouts of the blocks serve as trays for embedding lintels or filling belts, due to which high-quality perception of bending loads is ensured. The same goals can be achieved using conventional FBS blocks, between which, after 1-2 rows, reinforced belts are cast on attached formwork.

Problems of insulation and waterproofing

The main disadvantage of prefabricated foundations made of FBS is their low localizing ability. If it is necessary to equip a dry basement, the joints between the blocks pose a serious problem, and these are far from cold seams of monolithic concreting.

There are several ways to solve this. The main one is cutting the outer sides of the joints and laying a bentonite cord in them. However, even such efforts will not be enough if special concrete with low water absorption was not used in the production of the blocks.

In general, the insulation of prefabricated foundations is applied by surfacing using high-quality fabrics based on cross-linked polypropylene or fiberglass. In this case, the hydraulic barrier needs to be temporarily fastened in the upper zone of the foundation above the ground level, otherwise there is a high risk of its detachment due to atmospheric influences, because the foundation will remain open almost until construction is completed.

The problem of defrosting low-grade concrete can also be solved by insulating the outer surfaces of the foundation and blind area. For these purposes, ordinary inexpensive low-density PSB is used, which is temporarily attached to the blocks on top of the insulation using an adhesive method, and then supported by backfill soil.

The strip foundation for a house is deservedly considered one of the most reliable, durable and load-resistant. But it takes quite a long time to build - a couple of days to excavate the earth, a couple to assemble the formwork, plus at least twenty to harden the concrete solution. To speed up the construction process, developers often replace it with a prefabricated strip foundation made from factory-made FBS blocks. This option is much easier to do, and the time required for installation and installation is much less.

What is a foundation made of FBS blocks?

The structure of the FBS base is a masonry of concrete blocks of various sizes on a sand bed. A reinforced reinforced concrete belt is sometimes installed between the rows and on top of them, but many builders do without it. Plus, the foundation concrete is protected by waterproofing, standard for all structures in the ground.

This is what they look like

FBS are often called “wall”, but this is fundamentally wrong. It is more correct to call them “solid” or “solid section”. In fact it's reinforced concrete products block type, intended for the construction exclusively of foundations and basement walls. Build wall partitions from them residential buildings and other buildings it is strictly forbidden. They are too heavy for that.

Types of block foundations

It is recommended to choose it only for areas with dry and low-heaving soils. But in fact, with proper calculation, such a support can be installed for any house and on any soil. FBS blocks made of reinforced concrete were originally developed to speed up and simplify construction. They can withstand considerable loads, you just need to select them correctly.

This is what a block base looks like

On block foundation buildings can be erected from all known building materials. There are no restrictions here. But for the same house made of SIP panels, which is distinguished by its light weight, it is better to choose cheaper screw piles. But in general, on the base of the wall in question building regulations and the standards allow installation from brick, foam blocks, timber and logs. Everything is at the discretion of the cottage owner.

Advantages and disadvantages of FBS blocks

Among the advantages are:

High speed of work;

There is no need to mix concrete or order a concrete truck;

Applicability on almost all types of soil;

High factory quality of concrete products;

No need for formwork.

Foundation blocks are brought to the construction site in a form completely ready for work. You just need to lay out the masonry from them. There is no need to wait for the concrete to set and gain strength. In terms of speed of construction, such a foundation for a private house can only be surpassed by a foundation on piles. It is generally difficult to compete with this option.

The disadvantages of a FBS base are as follows:

Expensive compared to conventional monolithic tape analogue;

Difficulties in cutting concrete products into pieces of the required size;

The need to use special equipment (crane or winch).

The choice of FBS device is often determined by minimizing time costs. Plus, its construction can be carried out even in winter. However, this comes at the cost of having to use lifting equipment. It is impossible to manually lay the products into the foundation; they are too heavy. As a result, this option is 15–25% more expensive than its analogue monolithic tape.

A crane is required for lifting

The main thing is that when compared with a monolith, the block type of foundations for buildings is somewhat inferior in terms of load-bearing capacity. And while it can easily withstand high vertical loads, there are serious problems with horizontal ones. If there is severe heaving, the block can simply be squeezed out of the supporting structure.

Installation instructions

The concrete foundation is built with your own hands according to all the instructions in four stages:

Design and selection of blocks.

Excavation work with filling a cushion of sand.

Installation (with or without reinforcement).

Waterproofing.

It is better to entrust the preparation of the project to a professional. This will allow you to obtain a foundation with the desired characteristics with a minimum cost of materials. FBS are available in different sizes. However, if they are too large, there will be extra expenses and loads on the ground. These concrete products must be selected according to the specific parameters of future walls. But usually for the bottom row they take a width of 400 mm, and for subsequent ones above - 300 mm.

All foundation blocks are divided into four subtypes:

FBS - solid privates.

FBP - with voids at the bottom to reduce loads on the soil.

FBV – with a cutout along the length for communications.

FL – trapezoidal slabs for the bottom row.

According to GOST, in the marking after these letters there are three numbers (length-width-height in decimeters) and the letters “T”, “P” or “S”, indicating the type of concrete used. In the first case, this is a “heavy” option made of cement, sand and crushed stone. In the second, there is a “porous” analogue, in which expanded clay concrete is used as a filler. And in the third it is a “silicate” product made with the addition of lime. The construction of foundations is always carried out using class “T”. Only they have the necessary load-bearing capabilities and are not afraid of moisture.

The ground stage is standard. It is necessary to dig a trench to a depth below the freezing point of the soil on the site. Then, at its bottom, a cushion compacted from sand 30–40 cm thick is made for the subsequent laying of FL slabs. Here it is important to do everything so that the sand layer is horizontally at the same level throughout the entire length of the pit. Otherwise, the base will most likely end up distorted.

It is almost impossible to divide a concrete foundation block into two parts of the required size. If voids remain in the masonry during installation, they are usually filled with bricks and the opening is plastered. FBS in a row from above are always installed offset; through vertical seams are unacceptable here. For masonry, standard cement mortar with a grade of at least M100 is used.

If reinforcement is required, then it is necessary to lay 2–5 rods in one layer on top of the already assembled row. In this case, the same technologies are used as when constructing a strip foundation. Only the reinforcing belt turns out to be single-row.

For waterproofing, roofing felt or other rolled equivalent is laid on top of the top rows. Even a soft roof is suitable for these purposes, but it costs more. The sides of the masonry are completely coated with mastic. The waterproofing layer should cover the concrete on all sides to minimize exposure to moisture. This way it will last much longer.

Before you start building a block foundation for a cottage, you need to plan everything carefully. It is necessary to provide a platform for unloading blocks and a place for a crane. This means that special equipment is not required to install supports for a pile foundation or pour a monolithic tape. There is no way to do this without special equipment.

Unloading

We prepare the solution and supply the first one with a tap

Lower the first one along the tensioned level

Place the second one on top of the first one

We adjust the position manually using a crowbar

We arrange all subsequent ones in the same way.

Block foundation and its application

According to the estimate, a block structure is slightly more expensive than a monolithic tape, but it is built much faster. In terms of load-bearing characteristics, they are largely similar, the main thing is that the FBS from the side is not subject to too strong an impact during heaving.

The only thing that can be done faster than the option under consideration is a foundation on screw piles. But the latter is often chosen only for light buildings, for the construction of the walls of which SIP panels or lightweight aerated concrete are used. A block base is more versatile. It is not difficult to build it yourself. Presented above step-by-step instruction will allow you to complete everything, avoiding possible mistakes of beginners.