Bases made of prefabricated structures are widely used not only in industrial, but also in private construction. They are used in the construction of a private house, gazebo or cottage. Its main advantage is a significant reduction in construction time and the ability to immediately load the foundation after installation.
However, blocks for the foundation, namely their laying, are more expensive than monolithic foundations. However, this type of foundation does not have striking advantages. On the contrary, a large number of seams between the elements complicates the work on waterproofing the basement of the foundation.
In addition, when reinforced concrete blocks are used for the foundation, serious lifting equipment is required.
Types of structures
Previously, concrete blocks were produced exclusively in accordance with GOST 13579-78. But now manufacturers are allowed to produce them according to specifications in compliance with the requirements for dimensions. Reinforced concrete blocks used in the construction of foundations in the construction products market are represented by several varieties. Basically, the following types can be distinguished:
- F blocks are cylindrical columns and are used for vertical supports in pile/column foundations.
- FL blocks are trapezoidal elements used for the installation of a sole in a strip base and as supports for columnar foundations.
- FBS blocks are parallelepipeds with arcuate cutouts at the ends. This type of structure is used for basement walls with a residential basement, and for strip masonry.
- BF - designs of tee or trapezoidal section. These products are used when assembling the grillage of a columnar / pile foundation. Also, this type is applicable when arranging a base for a strip foundation of a house or a gazebo.
- FBP - hollow rectangular parallelepipeds. They are used as a lightweight material for the device of a precast concrete strip base. Such hollow blocks are also applicable for the formation of formwork for a monolithic tape. Usually they are reinforced with A-1 or A-3 steel of design or prestressing. These products are made from heavy silicate concrete on expanded clay concrete or porous aggregates.
- FR - used in the construction of frame structures. These are products of a reinforced type made of cement of durable grades: M500 and above.
In addition to the types listed above, there are small-sized foundation blocks (made of sand and concrete) that you can make yourself.
In their production, dimensions of 20x20x40 cm are used. For this, a solution of Portland cement and sand is kneaded in a ratio of 1: 3. The reinforcing filler is polymer fiber and gravel, where 5.5 parts fall on 1 part of cement. When forming products, vibration stands must be used.
The size and weight of these blocks (no more than 40 kg) allows them to be used for independent installation of a prefabricated foundation for a cottage or a summer gazebo. The base using sand concrete products is capable of carrying loads corresponding to the bearing capacity of bases of a monolithic tape type made of concrete grades 150, 200 and 250.
Aerated concrete and gas silicate
The construction time, the cost of materials and work, the operational characteristics of the house largely depend on the choice of the type of walls. The most popular products in the construction of walls of a low-rise individual house, garage, gazebo and cottage are wall materials made of cellular / porous concrete. Their frequent use is largely due to technical characteristics and economic benefits for the developer.
Aerated concrete blocks are produced industrially. For pouring into molds, a mixture of cement, aluminum powder, lime (quicklime) and quartz sand is taken. The filled molds are placed in autoclaves until completely cured.
The most common parameters of the finished product are 60x25x20 centimeters. For comparison: 1 block = 17 pcs. bricks, weighing 60 kg.
Features of porous concrete
Its main difference is the high porosity of the material, lighter weight (compared to brick), good ability to retain heat. In some respects, it can be compared to a tree.
Due to the porosity of concrete, good sound and thermal insulation is also achieved. Relatively light weight, significantly reduces the cost of performing work on the device bases.
In addition, aerated concrete and foam concrete blocks are fire resistant, unattractive to rodents and do not rot. The blocks are easily drilled, sawn, so it is easy to make a strobe for laying electrical wiring in them.
Foam concrete blocks
In the manufacture of these products, a mixture of sand, cement, water and technical foam is used. The well-mixed mixture is poured into molds and allowed to set.
At the end of the curing process, a material with closed pores is obtained. The manufacturing technology allows the production of blocks directly at the construction site.
The weight of the finished foam block is 31 kg, with standard dimensions of 20x30x60 centimeters. For comparison: 1 block = 15 pcs. bricks, the weight of which is 53 kg.
Main differences
Blocks of aerated concrete are laid on a special glue, and blocks of foam concrete - using cement mortar. The cost of glue is higher, but it will require much less than a solution. However, the cost of aerated concrete is higher than foam blocks. In total, at the end of the work, the cost of laying both the first and second types of blocks will be approximately the same. The pros and cons of foam concrete and aerated concrete can be reduced to the following:
- the adhesive used when laying aerated concrete has good thermal conductivity and does not reduce the characteristics of the blocks. The cement mortar used when laying foam blocks forms "cold bridges" between structural elements;
- the gas permeability of products in aerated concrete is much better, which allows the walls to "breathe". In comparison with it, foam concrete blocks absorb moisture worse, and they must be additionally tiled. This leads to additional costs in the construction of houses and gazebos;
- on the other hand, due to the fact that foam concrete does not absorb moisture, it has better frost resistance and thermal protection. These characteristics make the material suitable for the construction of structures with high humidity. Aerated concrete is not used or requires vapor barrier where condensation is possible;
From the point of view of ecology, foam concrete, which includes safe substances, is considered the safest. Aerated concrete contains aluminum powder, but when used correctly, they are also harmless to humans.
Expanded clay blocks
Arrangement of a prefabricated foundation with expanded clay concrete blocks Expanded clay concrete is a material with a slightly higher volumetric weight. Compared to gas / foam concrete, expanded clay concrete blocks weigh twice as much. The material used for manufacturing is a hollow fraction of baked clay, cement, sand and special fillers. Blocks have good indicators of durability and environmental friendliness.
Expanded clay products can be of two types: hollow or hollow. The performance characteristics of the house, gazebo or summer veranda depend on the type of blocks used. Although they are much lighter than bricks, the foundation must be designed to withstand the weight of the structure. The cost of products of this type exceeds blocks of foam concrete or aerated concrete by 10–20%, and they are more difficult to process.
But in terms of strength, they significantly exceed all other porous materials. Products made of expanded clay concrete are smaller in size, and when laid on cement mortar, numerous "cold bridges" are formed. The width of the walls of the cottages must be at least 40 centimeters, a smaller width, for example, 20 cm, can only be used with additional insulation or for a gazebo or veranda.
In addition, it should be remembered that full-bodied products have a lower sound insulation index than hollow ones. As for the vapor permeability index of expanded clay concrete, it is lower than that of other materials (aerated concrete, wood). The laying of walls from this material involves plastering or other facing work.
Any foundation is suitable for the construction of a building from expanded clay concrete elements , and its choice is determined by the characteristics of the soil and climate of the development region.
Right choice
For the correct selection of blocks for the foundation of a gazebo or house, one should take into account the climatic features of the region, soils, and requirements for the operation of the building. Do not purchase foundation blocks from unknown manufacturers. Quality products can only be manufactured in industrial production.
- Monitor enterprises located in relative proximity to the building site.
- Choose only trusted manufacturers.
- Require certificates of conformity and a product passport, or a copy of it.
- Consider the need to purchase products that have special openings for communications.
- Calculate the required number of blocks.
Remember that only products made of ordinary or heavy concrete are suitable for prefabricated foundations.
Prefabricated structures help to significantly reduce the construction time of any structures. Foundation blocks are intended, as a rule, for the construction of buildings with basements. They form the walls of the underground part of the building, at the same time being the basis of the future house. Blocks for the foundation are solid and hollow. And they are made of heavy, porous or silicate concrete.
Standards
Foundation blocks are produced in accordance with the standards prescribed in GOST 13579-78. Here are indicated:
- constructive types of concrete products;
- specifications;
- dimensional parameters;
- material requirements;
- permissible deviations;
- rules relating to acceptance and control;
- methods of storage and transportation.
Hollow blocks are produced under the FBP brand. In their body, along a length equal to 2380 mm, there are deaf notches that do not reach the closed edge of 30 mm. The height of the products is 580mm, and the width is 400, 500 and 600mm. The voids at the entrance have a rectangular cross section, narrowing as they go deeper. Their sizes:
- along the length at the entrance - 430mm, at the bottom - 350mm;
- in width at the entrance - 160, 220 and 320 mm, depending on the width of the foundation blocks;
- in depth - 550mm.
There are four holes in each FBP, passing from a rectangular shape in the open part to a rounded one in the closed one.
Foundation blocks have symbols indicating the type of products (in our case, FBP), three sizes in decimeters, rounded up, the type of concrete and the GOST number. For example: FBS 24.5.6-C GOST 13579-78. Such marking is considered standard, although industry regulations have the right to change it somewhat.
The type of concrete means:
- T - heavy;
- C - has an average density (silicate);
- P - is made using porous aggregates (expanded concrete).
All of the listed types of material are used for the production of foundation blocks with voids. The ratio of the type of concrete and its compressive strength class for FBP:
- for heavy and expanded clay concretes - B12.5;
- for silicate - B15.
The reference weight of products, in this case, is:
- from heavy concrete - 1.05 ... 1.4 t;
- from silicate - 0.88 ... 1.17 t;
- from expanded clay concrete - 0.79 ... 1.05 tons.
Frost resistance, as well as water resistance of concrete, is accepted according to building codes, depending on the climatic conditions of the region and the operation of the foundation. These explanations are given in the project documentation. Particular attention is paid to the geological conditions of the construction site. In particular, an important parameter is the aggressiveness of the environment. After the research, adjustments are made to the requirements for the composition of the concrete mixture from which the products will be made.
In all foundation blocks with voids, two mounting loops of grade P2 are laid. They are a reinforcing bar with a diameter of 10 mm bent in a certain way. GOST presents drawings and dimensions of loops. They are installed in special recesses at a distance of 80mm from the end of the block. On the surface of the protruding part of the rods, there should be no sagging of concrete.
Tolerances
The standards define the tolerances of linear dimensions in both directions:
- in length - within 13mm;
- in width - within 8mm;
- in height - within 8mm.
The straightness of the surfaces should not deviate by more than 3 mm along the entire length or width of the foundation blocks. In addition, no cracks are allowed in their body, except for minor surface defects.
Peculiarities
The use of hollow blocks, despite the apparent fragility of products, increases the reliability of the foundation. The fact is that its margin of safety increases due to the reinforcement of the structure with vertical reinforcing bars and as a result of filling voids with concrete mortar. The blocks, in this case, perform the function of a fixed formwork, entering into a fairly rigid monolithic adhesion to the concrete poured inside the structural holes. The foundation is strong and weakly reacts to the effects of lateral loads.
Professionals argue that FBP does not justify itself in low-rise construction.
Their arguments are as follows. Foundation blocks cannot be lifted manually, so a construction crane must be ordered for their installation. His work is estimated in machine hours, taking into account downtime, which is expensive for a private developer. In addition, for the transportation of products to the installation site, a truck is needed, and for the process of installing the blocks itself, a batch mixing of the solution is required. All these factors affect the rise in the cost of building a foundation from hollow blocks.
Prefabricated products have their undeniable advantages. But their full benefit is manifested in the construction of underground parts of high-rise buildings. In this case, the blocks provide:
- speed of masonry - no need to build formwork and wait for the final setting of concrete;
- clear geometry of basement walls due to standard sizes of industrial products;
- declared density and strength.
The voids of the FBP are filled not only with concrete, but also with insulation. This makes it possible to use blocks in the construction of foundation walls of unheated basements and even ground structures of industrial workshops or utility rooms that are not provided with central heating. In certain cases, hollow blocks are used as protective covers for pipelines of heating systems or water supply. In this case, the space between the pipes and the inner walls of the concrete blocks is filled with heat-insulating foam.
Boris R., Balashikha
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Elena L., Moscow
As a woman, all these construction issues are difficult for me to understand, but under the circumstances, you can’t learn anything. When I needed to buy paving slabs for my parents' plot, I looked for a long time about what and where to buy. Products are basically similar everywhere, but experience suggested that not everything is so simple. As a result, I opted for the Avtostroy company, which I do not regret.
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What can I say. Everything is fine, no problems, I ordered and bought paving slabs and curbs. Ordinary, gray, so I can’t say about the color. The quality is good, no chips, no, God forbid, cracks. Arrived the next day after ordering, free of charge. They themselves unloaded, the car was with a crane-manipulator. This was especially useful, given that I was alone and did not specify how the unloading would be carried out. But everything worked out, pallets with paving slabs and curbs were unloaded in a place convenient for me.
Before you make a foundation of blocks for a private cottage, it must be taken into account that the construction budget will hardly change compared to pouring into the formwork, but the work time will be reduced by a factor of three. The industrial method of production of FBS guarantees the maximum resource of the structure.
Do-it-yourself foundation can be made from FBS blocks only if there are lifting equipment (manipulator, crane). For a project with a basement, it is necessary to dig a foundation pit, if the building does not have a basement, there are enough trenches around the perimeter.
The production of FB is regulated by the domestic standard of 1978 under the number 13579, which specifies the material, dimensions, design features, rules for storage, transportation, installation. The main classification is made according to the design of reinforced concrete products:
- FBP - the block has voids open downwards to reduce structural loads on the ground;
- FBV - a cutout is provided for laying communications, mounting jumpers (relevant for technical subfields with numerous engineering systems);
- FBS is a solid block of increased strength.
All of them are made of concrete mortar with a density of 1.8 t / m 3 and have several sizes:
- length - 2.4 m, 1.2 m or 0.9 m (the size is slightly smaller, rounded off in the marking, indicated in decimeters);
- width - 0.3 - 0.6 m (step 0.1 m);
- height - 0.6 m or 0.3 m (modifications with voids, recesses only 0.6 m).
The mounting loop can be recessed into the body of the block or protrude above the upper edge (they are bent after installation). When storing, the standard requirements must be observed - pads made of wood 3 cm thick, a stack of 2.5 m, maximum.
Step-by-step instructions for building a foundation from FBS
To build a correctly prefabricated strip foundation, it is necessary to take into account the type of soil, total loads, groundwater level, number of storeys of the building. If FL foundation slabs are included in the project, it is easier to dig a pit if the blocks are mounted directly on the ground, a perimeter trench is sufficient. Its width should be more than 1 m for waterproofing, insulation of the outer walls of the tape, laying drainage pipes.
Training
We mark the pit
The device of a prefabricated strip base begins with a layout, without which it is impossible to mark the building spot. It is impossible to build a house without a project (the exception is a garden house), all design marks are available in this documentation. After planning the building spot, marking is carried out:
- pegs - driven in 0.5 - 1 m from the corners to avoid shedding the soil under them during excavation;
- cords - stretched along the outer perimeter of the walls, taking into account the design of the base (flush, protruding, protruding), the width of the FBS.
With a complex configuration of the cottage (bay windows, pilasters), local marking with lime, chalk, paint on the ground can be made.
Excavation
swarm excavation
To properly build a cottage, you need high-quality design based on the results of engineering and geological surveys. Only in this case there will be no third-party communications passing through the site under the foundation, the groundwater level, the composition of the soil will be known. This will create a strength margin of the structure.
The device of the pit is justified in the following cases:
- basement planned;
- the need for laying PL slabs;
- loose, weak, crumbling soil.
In all other options, you can get by with trenches under the walls of the cottage. The depth of the tape is always individual (0.3 - 0.7 m for MZLF, below the freezing mark by 40 cm for deep laying).
Substrate (drainage layer)
For high-quality support of concrete blocks / slabs, distribution of loads on the lower soil layers, it is necessary to replace the soil with non-metallic material. Usually this is a layer of crushed stone 15 cm of medium fraction (5-10 mm) over sand 15 cm, compacted in layers (10 cm) with a vibrating plate or manual rammer. Abundant wetting at the time of compaction reduces the time of work.
Pillow
Preparing the base for the pillow
The device of a concrete pad on the underlying layer in low-rise construction is extremely rare (for example, for a two-story mansion with an attic). The quality of the FBS is much higher than the monolithic design of the tape due to the exact observance of technology. Individual developers often do not have deep vibrators, concrete mixers, they save on fittings, forget to cover the set concrete with sand or sawdust for regular moistening to avoid cracks.
Pouring a structure
Reinforcing and pouring concrete pad
A step-by-step instruction for making a monolithic pillow looks like:
- installation of formwork - panels made of plywood, OSB, boards, wrapped from the inside with a film or roofing felt;
- reinforcement - two belts made of mesh, bars of a periodic profile with vertical jumpers;
- pouring concrete - must be done in one go, the maximum technological pause cannot exceed 1 hour.
The level of the concrete layer can be the upper side of the formwork or a line on its inner wall. Demoulding is possible after 4 - 7 days depending on the weather, installation of blocks only after two weeks. At the time of drying, concrete should be covered with sawdust, watered from a watering can for the first two days.
Prefabricated pillow from FL blocks
Instead of a pillow of a concrete monolithic pillow, special FL blocks can be used
Concrete slab pillow is more expensive, but its quality is higher by default. Installation of FL plates is carried out along a cord stretched along lighthouse corner reinforced concrete products. With a periodic layout of the slabs (intermittent foundation), they are placed at the corners of two adjacent FBS blocks. The gaps between them are filled with sand. Periodic layout saves money, but is not allowed on soft soils.
Installation of FBS blocks
We mount the blocks of the future foundation
The device for the assembly tape from the blocks begins after the preparation of the solution. The approximate consumption of the solution is 1.5 - 2 buckets, depending on the dimensions of the FBS. The tape construction technology is as follows:
- installation of corners - one row on a single level;
- installation of FBS near technological openings - necessary for the input of communications, ventilation products (only 30 - 50 cm above ground level);
- filling the rows - whole blocks are mounted on the mortar along the mooring cord, then pieces chipped off from them;
- laying with bricks - the height of the technological holes is less than the same parameter of the block, therefore, the free space is laid with clay or ceramic bricks, ventilation grilles, sleeves for sewer pipes, water pipes, and other engineering systems are embedded in the masonry.
Foundation thermal insulation
We glue the insulation
In 75% of cases, the prefabricated base tape is the walls of the basement or basement floor, technical underground. In this case, it is necessary to properly protect the walls of the underground level from condensate. The technology for warming the tape base of the house when it is deepened below the freezing mark is as follows:
- pasting the outer surface of the FBS blocks with extruded polystyrene foam over the waterproofing layer;
- covering with non-woven material to protect the heat insulator from accidental damage at the time of backfilling (dornite or geotextiles are usually used).
External insulation shifts the thermal circuit along with the dew point to the outside, the formation of condensate on the inner walls of the basement is completely excluded. Internal insulation leads to the opposite effect - it will not be possible to get rid of fogging of concrete, facings.
If the project includes a shallow MZLF tape, the technology changes slightly:
- after gluing the outer surfaces of the blocks with polystyrene foam, the trench is expanded outward by 0.7-1 m;
- the foundation along the perimeter is lined with horizontally arranged sheets of expanded polystyrene to a width of 1-1.5 meters.
Thus, even with a high level of GWL, heaving soil will not swell in frost. The heat of the bowels, preserved by the insulation around the perimeter of the building, will be enough to maintain a positive temperature under the sole of the cottage.
drainage system
For all concrete structures of the load-bearing frame of a dwelling, a decrease in the resource in aggressive environments is relevant. Therefore, with a high GWL or the possibility of increasing it during the operation period, it is better to divert groundwater from the foundation at the stage of excavation. To do this, it is enough to lay perforated pipes along the perimeter of the tape at the depth of the sole, organize the general slope of the ring in the direction of the underground tank, into which wastewater will flow by gravity.
When making a floor on the ground, the pit inside the tape is partially covered with soil taken out of it with layer-by-layer compaction to the design mark (-60 cm). This distance is necessary for the "pie" of the insulated slab / screed, which will be lined with flooring.
In the operated basement floor, the slab is poured at the level of the base of the foundation, the underground level is covered with a slab or structure along the floor beams. In this case, window openings may additionally be present in the basement. Instead of ventilation products, a full-fledged exhaust ventilation is made. It is impossible to place ventilation ducts inside the reinforced concrete blocks, therefore, a technological opening is left in the outer wall, the channel is passed inside the brickwork or special blocks, panels of GVL, light, heavy concrete, ceramics, silicate foam are used.
The assortment includes various types of products - solid for foundation masonry and hollow concrete blocks used for masonry walls. This material is a modern alternative to brick walls and foundations, while the characteristics of the blocks make it possible to simplify and speed up the construction of any object.
What determines the cost of concrete blocks?
If we compare the cost of concrete blocks presented by us with the price of other materials with similar characteristics, it becomes clear that the use of blocks is much more profitable. The relatively low cost of this material allows you to keep the affordable price of finished products.
Partnerships with leading factories allow us to keep selling prices for materials at an affordable level for most customers.
How much do building blocks cost?
The answer to this question depends on various factors. For example, hollow products are cheaper, since less cement is used to produce them than in the manufacture of monolithic solid foundation materials. From hollow blocks erect:
- walls;
- bearing structures;
- interior partitions;
- fences.
Full-bodied products are used for foundations, basements, basements. They are much stronger and more reliable, but more expensive. Also, the price of concrete blocks is affected by product dimensions, wall thickness, strength parameters, frost resistance, etc. All products offered by us have a high strength class corresponding to heavy concrete and frost resistance at the level of 50 cycles, which makes them reliable building materials.
