Solid (slab) foundations. Foundations of solid structure Foundations in the form of solid slabs

Today, any more or less serious building, erected in accordance with current technological standards, requires a foundation. Depending on the characteristics of the soil, the number of storeys of the building and some external factors, the type of foundation used is selected.

A monolithic solid foundation is poured in the case of building a building on loose soils with low bearing capacity and in places where groundwater is close to the surface. Examples of places where you can not do without the use of such a foundation are old landfills, soils prone to swelling, sandy areas. This type of foundation belongs to shallow ones, in addition, its use allows the building to obtain an acceptable support area on a small plot of land. This type of foundation is quite versatile - it is built both under heavy multi-storey buildings and under prefabricated panel structures of light weight. The main difference will be in the way the reinforcing bars are placed and the layout of the additional stiffeners.

Solid (slab) foundation technology

A solid (slab) foundation is a solid reinforced concrete slab placed over the area of ​​the entire building. It has a high bearing capacity and resists soil displacement well, actually moving along with the soil. It also enhances the resistance of the house to the loads that are likely to occur during land subsidence or temperature fluctuations.

General characteristics

The slab foundation is focused on complex types of soils:

• peated;
• waterlogged;
• water-saturated;
• weak-bearing;
• heaving;
• drawdown.

Stages of work

Work on the formation of a slab (solid) foundation allows both the pouring of concrete at the construction site, and the use of standard reinforced concrete slabs, which are used for laying roads. The main condition is a thickness within 20-30 cm. Depending on this, the construction includes several stages:

• preparation;
• site breakdown;
• formwork formation;
• reinforcement;
• pouring concrete.

Preparation

It consists in the development of documentation, the calculation of estimates, accurate planning and clearing the territory. In order to eventually receive a complete package of documents, it is best to contact specialists working in the profile. This will save time and money, as well as a professional approach to building a house, taking into account the type of recommended foundation. This is especially true when erecting the rear on soils with surface moisture.

In addition, the foundation for the foundation requires a balanced approach and clarification of all the details. Equally important is the ideal evenness of the surface. To do this, the site is first freed from shrubs and other vegetation, stumps and roots are removed, large stones and boulders are collected. Next, level it with a shovel and a level, removing protrusions and recesses.

Plot breakdown

This stage consists in transferring the plan to the area. For this, a geodetic breakdown and setting of key marks of the future building is carried out. Next, the entire top layer of the earth is removed. It has a low bearing capacity and a high compressibility. That is why it is removed to a depth of half a meter. The work is carried out with the help of an excavator.

To fill the pit, a gravel-sand or crushed-stone-sand mixture is used at the rate of 60:40, respectively. It is tightly packed. This pillow:

• makes it possible to reduce the force of frost heaving on the lower zone of the foundation;
• allows ground moisture to pass unhindered under the house;
• evenly distributes the pressure of the building on the soil.

In addition, the sandy base does not retain water, and the low “seated” structure does not allow the soil to freeze during the cold season, providing the structure with increased stability. Then trenches are laid across the foundation (for reservoir drainage) and lined with geotextiles. Gravel is poured over it.

Formwork and reinforcement

Rotary sealed wells are installed at the corners of the resulting “structure”, since the slab bases lie mainly on soils with a high moisture content and the maximum proximity of groundwater. Then proceed to the basic formwork. According to calculations, it should go beyond the perimeter of the foundation by 15 centimeters.

The bottom of the pit is covered with granite gravel of a fraction of 4-6 cm. The maximum thickness of the layer can reach 20 cm. A small 4-cm layer of concrete is formed on top of it, which is the first screed. But before that, the crushed stone is shed with a liquid mixture of sand and concrete so that the outer layer forms an even “crust”.

Next, move on to waterproofing. These can be special rolled materials with adhesions or a conventional bituminous primer that is coated with cement. Any rolled waterproofing agent is glued onto it. On top of the mastic in 2 layers, a gluing built-up waterproofing spreads. If desired, you can make and insulating layers.

Then they begin to form the formwork for a monolithic reinforced concrete slab. To do this, racks are dug in around the entire perimeter of the structure and any plank materials are nailed to them. During this operation, a level is required.

The base of the foundation slab is a special metal frame with reinforcement over the entire area. For these purposes, two iron grids are used - lower and upper. Their bundle is performed with special hooks and annealed steel wire.

Then, between the main mesh rods, additional ones are installed, at a distance of 20 cm from each other. Plastic compensators or clamps are also mounted, ensuring the best location of the steel bars.

Pouring concrete

Pouring concrete is the final stage of work on the slab foundation. In the course of its implementation, both ready-made dry mixes and self-mixing solutions can be used - based on cement, sand and gravel (crushed stone). They fill the formwork strictly to the height of the sides. After drying, the plates proceed to the next stage of construction.

Foundations are the supporting part of the building and are designed to transfer the load from the overlying structures to the foundation.

The foundations of the building must meet the following basic requirements: have sufficient strength and resistance to tipping and slipping in the plane of the sole, resist the influence of atmospheric factors (frost resistance), as well as the influence of ground and aggressive waters, correspond in terms of durability to the service life of the building, be economical and industrial in manufacture .

Having broken a place under the foundation of the building, proceed to excavation. The construction of the foundation is recommended to be carried out immediately after excavation. Drying, the earth in the trench crumbles and it takes a lot of time to remove it.

By design, the foundations are: solid, tape, columnar and pile.

solid foundations

They are a solid non-block or ribbed reinforced concrete slab "under the entire area of ​​​​the building. Solid foundations are suitable in cases where the load transferred to the foundation is significant, and the base soil is weak. This design is especially appropriate when it is necessary to protect the basement from the penetration of groundwater at a high level if the basement floor is subjected to high hydrostatic pressure from below.

Rice. 1 Solid beamless foundation:

1 - reinforced concrete foundation slab

They are arranged under the walls of the building or under a number of individual supports. In the first case, the foundations have the form of continuous underground walls (Fig. 3a), in the second - reinforced concrete cross beams (Fig. 3b).

In its outline in the profile, the strip foundation under the stone wall is in the simplest case a rectangle (Fig. 4e). The rectangular section of the foundation in height is permissible only with small loads on the foundation and a sufficiently high bearing capacity of the soil.

In most cases, in order to transfer pressure to the base that does not exceed the normative pressure on the soil, it is necessary to expand the base of the foundation. The theoretical sectional shape of the foundation with an expanded sole is a trapezoid (Fig. 46). The expansion of the sole should not be too large in order to avoid the appearance of tensile and shear stresses in the protruding parts of the foundation and the appearance of cracks in them.

Rice. 3. Foundation structures:

A - foundation in the form of continuous underground walls: 1 - strip foundation; 2-wall; b-in the form of cross reinforced concrete beams: I - strip foundation for columns; 2 - reinforced concrete column

On the basis of experience, the angles of inclination of the theoretical side face of the foundation to the vertical were established, along which no dangerous tensile and shear stresses arise. The limiting angle, conventionally called the pressure distribution angle in the foundation material, is 45 ° for concrete, masonry with a cement mortar of composition 1: 4 - 33 ° 30 ", for rubble masonry with a complex mortar of composition 1: 1: 9 - 26 ° 30?.

In buildings with basements, the section of the foundation within the basement is arranged in a rectangular shape with an extension below the basement floor, called a pillow (Fig. 5 a). Often, foundations are made with a stepped section (Fig. 5 b).

The depth of the foundation should correspond to the depth of that layer of soil, which, by its qualities, can be taken for a given building as a natural foundation. When determining the laying of the foundation, it is necessary to take into account the depth of soil freezing. It is recommended to lay foundations below the freezing depth. If the base consists of moist fine-grained soil (dusty or fine sand, sandy loam, loam, clay), then the base of the foundation is located no higher than the freezing level of the soil.

The level of soil freezing is taken at a depth where a temperature of 0 ° C is observed in winter, with the exception of clay and loamy soils, for which the level of freezing is taken at a shallower depth, where a temperature of about -1 ° C occurs.

The standard freezing depth of loamy and clayey soils is indicated in SNiP 2.02.01-83 on a schematic map in which lines of the same standard freezing depths are plotted, expressed in centimeters. The standard freezing depth of silty and fine sands, sandy loams, silty clays and loams is also taken from the map, but with a coefficient of 1.2.

Fig 4. :
a - rectangular; b - trapezoidal: 1 - cut

Fig 5. Strip foundations:

A - rectangular with a pillow; b - stepped with a pillow (1)

Studies have established that the soil under the foundations of the outer walls of regularly heated buildings with a room temperature of at least +10 ° C freezes to a lesser depth than in an open area. Therefore, the estimated depth of freezing under the foundations of a heated building is reduced against the standard value by 30% with floors on the ground; if the floors are on the ground on logs - by 20%; floors laid on beams - by 10%.

The depth of laying under the internal walls of heated buildings does not depend on the depth of soil freezing, it is assigned at least 0.5 m from the basement floor or ground level.

The depth of laying the foundations of the walls of buildings with unheated basements is assigned from the basement floor, it is equal to half the calculated freezing depth. The assumption that the deeper the foundation is laid, the greater its stability and reliability of operation, is incorrect.

When the base of the foundation is located below the level of freezing of the soil, the vertical forces of frost heaving cease to act on it from below, but the tangential forces of frost heaving acting on the side surfaces can pull the foundation together with the frozen soil, and tear it off under light buildings when building foundations made of bricks and small blocks.

Therefore, for the successful operation of the foundation, in order to prevent its deformation in heaving places, it is necessary not only to place the sole below the level of soil freezing, which will relieve the direct pressure of the frozen soil from below, but also to neutralize the frost heaving tangential forces acting on the side surfaces of the foundation. Inside the foundation, a reinforcing cage is laid to its entire height, rigidly connecting the upper and lower parts of the foundation, the base is made expanded in the form of a supporting platform-anchor, which does not allow the foundation to be pulled out of the ground during frost heaving of the soil. This constructive solution is possible when using reinforced concrete.

When building a foundation of bricks or small blocks, without internal vertical reinforcement, the walls are made sloping-tapering upwards. The above method of constructing foundation pillars and walls, with careful alignment of their surfaces, significantly weakens the lateral vertical effect of heaving soils on the foundation. The influence of frost heaving forces is reduced by: coating the side surfaces of the foundation with a sliding layer of polyethylene film; used engine oil; insulation of the surface layer of soil / around the foundation with slag, foam plastic, expanded clay, which reduces the local depth of soil freezing. The latter is also applicable to shallow foundations built earlier and in need of protection from frost heaving.

On a large-falling terrain, during the construction of a building, it is necessary to take into account the lateral pressure of the soil and its probable shift. Strip foundations rigidly connected in the longitudinal and transverse directions work more reliably under these conditions. Columnar foundations must be rigidly united on top with a reinforced concrete belt - a grillage, for more efficient joint work of all structural elements. In gravelly, coarse and medium-sized sands, as well as in coarse-grained soils, the depth of the foundation does not depend on the freezing depth, but it must be at least 0.5 m, counting from the natural level of the soil (planning mark when planning by cutting and backfilling).

In modern construction, the most industrial are prefabricated concrete and reinforced concrete foundations from large foundation blocks. The use of prefabricated foundations can significantly reduce construction time and reduce the complexity of work. The prefabricated foundation (Fig. 6) consists of two elements: a pad of reinforced concrete blocks of a rectangular or trapezoidal shape (Fig. 7)t laid on a carefully compacted sand preparation 150 mm thick, and a vertical wall of blocks in the form of concrete rectangular parallelepipeds.

Rice. 6. Prefabricated strip foundation of concrete blocks under the walls of the house with a basement and a technical underground:

I - foundation slab; 2 - concrete wall blocks; 3 - coloring hot
bitumen; 4 - cement-sand mortar; 5 - blind area; b - two layers of roofing paper go
hydronsol on bituminous mastic; 7 - basement

Rice. 7. Foundation block cushion

When building on weak highly compressible soils, in prefabricated foundations, to increase resistance to tensile forces and rigidity, reinforced concrete belts 100-150 mm thick or reinforced seams 30-50 mm thick are arranged, placing them between the pillow and the lower row of foundation blocks, as well as at the level of the upper foundation cut.

Foundation walls, assembled from large blocks, despite their great strength, are sometimes thicker than the above-ground part of the walls. As a result, the strength of the material is used by only 15-20%. Calculations show that the thickness of the walls of prefabricated foundations can be taken equal to the thickness of the above-ground walls, but not less than 300 mm.

Savings on building materials can be achieved by installing discontinuous foundations, consisting of reinforced concrete pillow blocks, not laid close, as provided for in strip foundations, but at a certain distance from one another, approximately from 0.2 to 0.9 m. blocks are covered with soil.

Pillar foundations

They have the appearance of separate supports arranged under walls, pillars or columns. With minor loads on the foundation, when the pressure on the ground is less than the standard, it is advisable to replace the continuous tape walls of low-rise buildings with columnar ones. Foundation pillars made of concrete or reinforced concrete are covered with reinforced concrete foundation beams on which the wall is built. To eliminate the possibility of bulging of the foundation beam due to swelling of the soil located under it, a sand or slag cushion 0.5 m thick is arranged under it.

The distance between the axes of the foundation pillars is assumed to be 2.5-3 m. The pillars must be placed at the corners of the building, at the intersection and junction of the walls and under the walls.

Columnar foundations for walls are also erected in high-rise buildings with a significant depth of foundation - 4-5 m, when the construction of a strip continuous foundation is unprofitable due to its large volume and, consequently, greater consumption of materials. The pillars are covered with prefabricated reinforced concrete beams, on which the walls are erected. Columnar single foundations are also arranged for individual supports of buildings. Figure 8a shows a prefabricated foundation for a brick pillar, made of reinforced concrete pillow blocks. A more economical option is to lay reinforced concrete blocks-slabs under brick pillars (Fig. 8 b). Prefabricated foundations for reinforced concrete columns of frame buildings can consist of one reinforced concrete glass-type shoe (Fig. 8c) or from a reinforced concrete block-glass and a base plate under it (Fig. 8d).

Pile foundations

They consist of separate piles, united from above by a concrete or reinforced concrete slab or beam, called a grillage (Fig. 9). suit in cases where it is necessary to transfer significant loads to weak soil.

Fig 8. Prefabricated foundations for individual supports:
a - under brick pillars from blocks of strip foundations; b - the same, from special reinforced concrete slabs; c - under a reinforced concrete column from a glass-type shoe; g - the same, from a glass block and a base plate

Piles are differentiated according to the material, method of manufacture and immersion in the ground, the nature of work in the ground. According to the pile material, there are wooden, concrete, reinforced concrete, steel and combined. According to the method of manufacturing and immersion in the ground, piles are driven, immersed in the ground in finished form, and stuffed, manufactured directly in the ground. Depending on the nature of the work in the ground, two types of piles are distinguished: piles - racks and hanging. Piles-racks with their ends rest on solid ground, for example, rock and transfer the load to it (Fig. 10). They are used when the depth of solid soil does not exceed the possible length of the pile. Pile foundations on pile-racks practically do not give sediment.

If solid soil is located at a considerable depth, hanging piles are used, the bearing capacity of which is determined by the sum of the resistance of the friction forces along the side surface and the soil under the pile tip (Fig. 11).

Rice. 9. Types of piles in the ground:

A - hanging piles; b - pile-racks: 1 - dense limestone; 2 - silty plastic loam; 3 -.silt; 4 - silty sand; 5 - peat; 6 - plant layer

Wood piles are cheap, but because they rot quickly if they are in soil with varying moisture, the heads of wood piles should be placed below the lowest level. However, in areas with a high level of groundwater, wooden piles last a very long time if they are constantly in the water. In world practice, there are examples of four-hundred-year-old buildings on wooden piles, which are still in good technical condition.

Reinforced concrete piles are durable, more expensive than wooden ones, but they can withstand significant loads. The scope of their application has been significantly expanded due to the fact that the design mark of the heads of reinforced concrete piles does not depend on the level of groundwater. The distance between the axes of the piles is determined by calculation. Within the limits of the most common pile insertion depths - from 5 to 20 m, these distances for ordinary pile diameters range from 3...8d, where d is the pile diameter.

Fig 10. Driven pile-stand of the foundation:
I - waterproofing; 2 - the surface of the earth; 3 - reinforced concrete grillage beam; 4 - driven pile of rectangular section; 5 - dense soil

Rice. 11. Stuffed hanging pile foundation:
1 - waterproofing; 2 - reinforced concrete beam grillage; 3 - stuffed pile; 4 - tip of the casing pipe; 5-weak soils

Pile foundations, in comparison with block foundations, give less settlement, which reduces the likelihood of uneven soil deformations.

When preparing the foundation, sometimes old filled-in wells, pits, random weak layers of soil are found in the ground. In order to avoid uneven settlement of foundations, these places must be cleared and filled with masonry, lean concrete or compacted sand, and when building foundations, reinforced seams should be applied over these places.

Foundations are exposed to moisture seeping through the ground atmospheric moisture or groundwater. Due to capillarity, moisture rises up the foundation and dampness appears in the walls of the first floor. To block the penetration of moisture into the walls, an insulating layer is arranged in their lower part, most often from two layers of bituminous rolled materials (roofing material, etc.), glued together with waterproof bituminous mastic.
During the operation of the foundations, it is necessary to monitor the settlement of the base and possible deformations.

Cellars

One of the important conditions for the safety and integrity of the house is waterproofing the basement. The walls and floors of basements, regardless of the location of groundwater, must be isolated from surface water seeping through the soil, as well as from capillary groundwater rising up. In basements, when the groundwater level is below the basement floor, sufficient waterproofing of the floor is its concrete preparation and a waterproof floor made on it, and waterproofing the walls is covering the surface in contact with the ground with two layers of hot bitumen. If the groundwater level is above the basement floor, in this case the water pressure is created the greater, the greater the difference between the levels of the floor and groundwater. In this regard, for waterproofing the walls and floor of the basement, it is necessary to create a shell that could resist the effects of hydrostatic pressure.

An effective measure to combat the penetration of groundwater into the basement is a drainage device. The essence of the drainage device is as follows. Ditches are arranged around the building at a distance of 2-3 m from the foundation with a slope of 0.002--0.006 towards the prefabricated drainage ditch. Pipes (concrete * ceramic or others) are laid along the bottom of the ditches with a slope. There are holes in the walls of the tubes through which water penetrates.

Ditches with pipes are covered with a layer of coarse gravel, then a layer of coarse sand and top-open ground. Through pipes laid in ditches, water flows down into the lowland (ditch, ravine, river, etc.). As a result of the drainage device, the groundwater level decreases.

When the groundwater level is not higher than 0.2 m from the basement floor, waterproofing of the basement floor and walls is arranged as follows. After coating the walls with bitumen, they arrange a clay castle, that is, before filling the trenches, crumpled greasy clay is hammered close to the outer wall of the basement. Concrete floor preparation is also laid on a layer of crumpled greasy clay.

At a height of the groundwater level from 0.2 to 0.5 m, gluing waterproofing is used from two layers of roofing material on bituminous mastic (Fig. 12). The insulation is laid on the concrete preparation of the floor, the surface of which is leveled with a layer of cement mortar or asphalt.

Since the floor structure must withstand a sufficiently large hydrostatic pressure from below, a concrete load layer is laid on top of the insulation, which balances the water pressure with its weight. On the outer side of the walls, insulation is glued on bituminous mastic and protected with 1/2 brick masonry of iron bricks on cement mortar and a layer of wrinkled greasy clay 250 mm thick.

Gluing insulation of the outer walls of the basement is placed 0.5 m above the groundwater level, taking into account its possible fluctuation.

Fig 12. Waterproofing strip foundation in a building with a basement:

1 - layer of load concrete; 2 - concrete preparation; 3 - roll waterproofing; 4 - crumpled greasy clay 250 mm; 5 - masonry of iron bricks on cement mortar 120 mm; 6 - double layer of bitumen

Rice. 13. Waterproofing strip foundation in a building with a basement:

1 - concrete preparation; 2-reinforced concrete slab; 3-roll waterproofing;
4 - crumpled greasy clay 250 mm; 5 - iron brick masonry on cement
solution 120 mm; b - double layer of bitumen

If the groundwater level is located more than 0.5 m above the basement floor, then a reinforced concrete slab is laid on top of the floor waterproofing, which is made of three layers of roofing material or hydroisol (Fig. 13). The slab is embedded in the basement wall, which, working on bending, perceives the hydrostatic pressure of groundwater.

With a high level of groundwater, the external waterproofing device sometimes causes difficulties. In such cases, it is performed along the inner surface of the basement walls (Fig. 14). The hydrostatic head is perceived by a special reinforced concrete structure - a caisson.

Rice. 14. Basement waterproofing at high groundwater pressure;

1 - roll insulation; 2 - concrete preparation; 3 - cement layer; 4 - cement screed; 5 - reinforced concrete box structure; 6 - clean floor; 7 - cement plaster over bituminous coating; 8 - waterproofing

Necessary features that are taken into account in the construction of foundations and the construction of plinths

When laying foundations of any type, the following rules must be observed:

Most foundation structures use concrete. Concrete has the property of "maturation", 28 - 30 days. After laying the concrete structure, it must be kept for a given time without loads and it is desirable to close it either with roofing felt or other available material from drying out the top layer. During the concrete setting period, periodically water the foundation with water to prevent uneven drying. So building a house on a newly erected foundation is fraught with danger, defects will not keep you waiting.

Foundation waterproofing is essential. It consists in coating with hot bitumen the entire surface in contact with the ground. Walls are also insulated. For this, two layers of roofing material are laid (1st layer - between the basement and the zero level; 2nd layer - between the basement and the main wall of the house). This protects the walls of the house and the basement from moisture.

Protection of the outer side of the plinth from atmospheric influences. This is achieved by plastering or tiling. To grout the foundation, rubber-containing components (ash from burnt tires) are added to the mixture. It turns out a "fur coat" for the base. She is beautiful and reliable.

During the construction of the plinth, ventilation holes are provided. In summer they serve to ventilate the underground, and in winter they are closed so that dampness does not get into the house.

The blind area is necessary to protect the foundation from the effects of surface water. The width of the blind area is from 0.75 to 1 meter with a slope from the basement wall. As materials are used: reinforced concrete, asphalt, concrete or well-compacted clay.

The device for draining rainwater from roofs also affects the strength of the foundation. Rainwater from the roof enters the blind area, breaks it and the basement gradually, unevenly moistens the soil near the foundation. This affects the bearing capacity of the foundation and contributes to subsidence of the foundation.

With all the modern variety of types of foundations and their advantages, many bath builders still prefer monolithic. After all, what is integral is always stronger than prefabricated structures. And the construction process in this case is somewhat simpler. And the most popular foundation is a monolithic slab, which is so reliable that even skyscrapers are built on it.

What is good about this type of foundation?

Monolithic foundations are always strong and can withstand heavy loads. They are not afraid of either uneven ground movements, or constant heavy rainfall, or severe freezing and thawing. The bath will simply rise and fall along with the foundation, without destroying any supports. After all, it is known that concrete works only in compression - and by no means in expansion. That is why the foundation in the form of a monolithic slab is practically indispensable for heaving and sandy soils, where the level of groundwater is high.

Yes, for timber, frame and log baths such a foundation is in some cases a luxury - if the soil is normal, then it is easier to make a tape shallow foundation. But the Russian bath itself has long ceased to be just a hut - its own overall bath complexes with pools and whole billiard rooms are in fashion. And under a massive steam room, a slab monolithic foundation is what you need.

Varieties of monolithic foundation designs

The monolithic foundation has several types. The most popular is slab, which is also subdivided into a simple slab and a slab on a ribbon, similar to an inverted bowl, which is becoming more and more popular abroad day by day.

But in terms of building a bath, it is precisely such a device of a monolithic foundation that has proven itself best so far - a monolithic slab of a simple scheme. Its main advantage is that there is no need to put it below the freezing depth of the soil - and this is a significant reduction in the cost of building materials and reliability in case of sudden changes in air temperature.

A slab monolithic foundation is essentially a solid reinforced concrete slab, which is buried in the ground. Both external and internal walls of the bath are built directly on this slab. And thanks to the uniform distribution of the entire load on the plate area, the pressure on the ground is minimized - the same physical law works here when a person in boots falls into the snow, but not on skis, because the pressure area is already larger. The design of the plate is so versatile that it is suitable even for frank peat bogs and even swamps. And most importantly, any mistakes are practically excluded in the construction of such a foundation, and therefore it is the best suited for private construction. Including - for the bath, because the amount of earthwork in this regard is minimal, and the basement of the steam room is not particularly needed.

Another type of monolithic foundation is a columnar monolithic one, which is being built for light baths. In fact, this is a single structure of the grillage and the pillars communicated by it.

But the tape monolithic foundation with a basement is able to withstand fairly large loads and feels good in the most adverse climatic conditions due to the fact that it copes well with subsidence, thawing and ground vibrations. In fact, this is a reinforced concrete strip that runs along the entire perimeter of the building. It can be shallow and deep. The first option is suitable for a log cabin and a bar, but the second one is for brick two-story steam rooms with considerable weight.

Stages of construction of a reinforced concrete slab

The process of building a monolithic foundation is much simpler than building prefabricated ones. But there is an important point: all materials used must be of the highest quality, because more serious requirements are imposed on a monolithic foundation. But at the same time, the involvement of construction equipment is not necessary!

Stage I. Site preparation

First of all, you need to clear the site well: remove the top layer of soil with vegetation, for which you can hire a bulldozer.

The thickness of such a foundation, or rather, a monolithic slab, can vary from 15 to 40 cm. It depends on the characteristics of the soil, the weight of the future bath and what it will be filled with.

Stage II. Digging a pit

Usually a foundation pit for such a foundation is dug to a depth of 1.5 meters, clay is pulled out from there and replaced with gravel or sand. The surface should be leveled according to the building level - there can be no talk of any slopes, otherwise deformation and complete destruction of the future foundation cannot be avoided.

Stage III. Formwork installation

Sometimes such foundations are built from ready-made monolithic reinforced concrete slabs, which can be seen during construction in a panel house. They already have a clearly calculated quality, but for their installation you will have to call a crane and still make a concrete screed over everything. And such a design will no longer be as rigid as an absolutely monolithic slab.

And for a do-it-yourself building, formwork is initially needed. For it, you will need boards with a thickness of at least 25 mm plus mowing. The formwork itself must be installed with supports - and it is advisable to initially check the rigidity of the entire structure. This can be done with an elementary kick - if the formwork breaks, it is better at this stage, and not during concreting.

Stage IV. Warming and waterproofing

Here it is worth mentioning the Swedish technology for the construction of such a foundation - it involves the use of modern heat and waterproofing materials. Such a base is called an insulated slab, which has amazing energy-saving properties with short construction times and low costs. For a Russian bath - that's it!

Stage V. Reinforcement

The next step is to mount the armature. Sometimes a floor heating system is additionally attached to a special grid.
Reinforcement is best taken 16 mm - in extreme cases, you can, of course, 14 mm. But it is not so easy to calculate it - it is better to do it in advance.

It is necessary to lay the reinforcement cross-by-cross, in two rows. This will result in two grids - one from below, 5 cm from the surface of the sand cushion, and the second from above, 5 cm from the surface of the foundation slab. Between the bars in the grid should be exactly 20 cm. You need to knit the reinforcement with ordinary steel wire.

Stage VI. Foundation pouring

You need to fill it in in one go, and it should only be of a high strength class - from M300 by brand, with a water resistance coefficient greater than W8 and frost resistance from F200 and a mobility index of P3. There is an important point here - all materials used must be of the highest quality, because more serious requirements are imposed on a monolithic foundation. In total, it will take somewhere at least 20 cubes of concrete.

As soon as the slab dries, the concrete floors in the bath will be completely ready for finishing. What is the biggest plus of a monolithic foundation - a minimum of hassle, a maximum of result!

At the moment, even a small building requires a solid foundation. It acts as a guarantee of structural strength and durability. But when building a house or other similar structure, the same question arises: what is the best foundation to use and what technology should be used to fill it? The answer lies in a number of factors: the number of floors in the building, its area, weight, soil features, and much more. But in the vast majority of cases, the best option is a solid foundation. We will talk about how to do all the work on filling it yourself, below.

The most demanded is a solid monolithic foundation in unstable soils - they have a weak bearing capacity. It is also great for places where water is close to the surface. It is also indispensable for construction in old landfills, in sandy areas and where the soil is prone to significant swelling due to temperature changes. It is simply necessary when a building is erected on subsiding, weakly bearing, swampy, peaty soils. The main advantage of such a foundation is obtaining an acceptable footprint on a relatively small piece of land. It is used in the construction of both massive heavy houses and small private buildings. The foundation is really universal and can be used in almost any conditions, which is a big plus. How is the tiled foundation? Peculiarities The standard solid foundation device is a solid reinforced concrete slab, which is placed over the area of ​​the building under construction. In fact, such a structure can partially move with the soil without losing its shape and strength. Such a monolithic structure significantly increases the resistance of the building to any loads that may appear due to subsidence of the earth or changes in weather conditions, which is very important for our climate zone with cold winters and hot summers. The tiled foundation consists of three main elements: armature D12 A3; geotextile; sand cushion. How to lay a solid foundation with your own hands? Stages of work The main thing to remember is that at all stages of construction, in order to avoid unpleasant consequences, you cannot do anything at random. An accurate calculation and application of knowledge in practice according to a prepared plan will allow you to do what every man is obliged to do - to build a house. Start with calculations of key parameters The first thing you need to do is to calculate the solid foundation with maximum accuracy. You must determine how thick the slab will be, as well as the area and depth at which it will be laid. Keep in mind that the area of ​​\u200b\u200bthe plate is slightly larger than the area of ​​\u200b\u200bthe house being built. It is best when it is wider by one or two meters in each direction. This will not be a strong blow to your budget, but it will significantly add strength to the building. The area of ​​​​the foundation is calculated relative to the total weight of not only the building, but also the foundation itself. Do not forget that he puts pressure on himself. It is also necessary to take into account the bearing capacity of the soil where construction will take place. For ordinary dry soil, it is approximately 2 kg per 1 cm 2. Important! Be sure to also take into account the weight of the floors between the rooms in the house, the roof and even ordinary snow, which for several months of the year will put pressure on the building from above. Please note that there will still be furniture, appliances and the residents themselves. Thus, another 150 kg / m 2 must be added to the resulting weight. When you get the total weight of the future building, divide it by the area. Now you can calculate the parameters of the foundation, also taking into account the type of soil. If your house is planned to have two floors, the calculation remains the same. If the weight is 300 tons, and the area is 100 m 2, then the load per 1 cm 2 will be 300 g. In this case, if you use M500 concrete, the foundation can be quite thin - about half a meter. The strength of concrete is 150 kg per 1 cm 2. Preparatory work The construction of the foundation takes place in several stages: First you need to completely clear the site chosen for construction from all foreign objects. The surface should be as even as you can ensure this. To achieve the optimal result, you will definitely have to use a level. Although not the fastest, but the free way is to level the surface with a shovel. We recommend purchasing all materials for work in advance so that the process is not interrupted for additional purchases. When the surface becomes even and you completely clean it all of third-party objects, you can start marking. In key places it is necessary to fix marks. You also need to remove the top layer of soil. It's about half a meter. The top soil has a weak bearing capacity, so it should be disposed of immediately. The process is time-consuming, so we advise you to use an excavator or involve other people in the work. It will take a lot of time and effort on your own. When you prepare the pit, lay a pillow of sand and gravel on its bottom. You can use crushed stone instead of gravel. The ratio of quantity becomes 2:3. This pillow needs to be tamped tightly. Thanks to it, the pressure on the soil is distributed evenly, moisture from the soil will freely go under the house, and the force of frost heaving of the foundation will decrease. Lay trenches for reservoir drainage along the future foundation. Geotextiles must be laid on their bottom, and crushed stone should be poured on top. We also recommend placing plastic pipes in the trenches. They also need to be sprinkled with crushed stone, and so that they do not become clogged, protect them with the same geotextile. But before pouring a solid slab foundation, you will need to do one more set of works. Reinforced frame and formwork Install excavation swivel wells in the corners. The fact is that the foundation, most likely, will stand on soil with high humidity. Water will accumulate next to it. To avoid collecting water under the entire foundation, formwork is also installed. It must be installed in such a way that it extends beyond the intended foundation by at least 15 cm. Now it is necessary to fill up another layer of rubble (20 cm) at the bottom of the pit. Pour about 4 cm of concrete on top of it - it will act as the first screed. Before pouring concrete on crushed stone, we recommend also pouring a mixture of concrete and sand - this will level the surface. Form the formwork for pouring concrete. To do this, along the entire perimeter of the foundation, you need to dig in racks, and nail any boards to them. Be sure to do this according to the level. To form a reinforced frame, you will need two iron meshes: lower and upper. They must be connected with vertical rods, which are placed 20 cm apart. To connect them, use a special knitting wire. We do not recommend welding. In this case, bridges are formed that are highly susceptible to corrosion. Only now can the foundation be poured, the solid slab of which, thanks to the previous steps, will be a really reliable support. Slab pouring This is the final and one of the most time-consuming stages of creating a solid foundation. It will take you a lot of time and effort to do it. If possible, take a couple of assistants who will help you prepare the mortar and pour it into the formwork. To prepare the mixture, use ready-made dry mixes, concrete ordered from manufacturers or prepared on your own. Make a choice depending on your budget, time and effort. You will need cement, gravel and sand for concrete. Gravel can be used instead of gravel. Pour the finished concrete into the formwork up to the very sides. Important! Keep in mind that already after 3-4 hours the concrete begins to set and harden, so everything must be done as quickly as possible, and the mortar should be prepared right before you pour it. The foundation is ready! Features of columnar foundations It is also necessary to say a few words about the use of columnar foundations, because columnar and solid foundations are quite similar to each other, and the technology for creating both is quite simple, for which it has earned great popularity. Consider the key differences and features of the fill. Also start work with clearing the territory and initial marking. Determine the number of posts to be installed and dig holes of at least 0.6 m in the right places. The depth depends on the properties of the soil. Difficulties arise only in swampy areas. Here you need to make a base about a meter deep and at the same time a little wider. Cut the reinforcement according to the height of the foundation pillars and the roofing material, which must be rolled into a tube with a diameter of about 10 cm (it is better to make two layers) and wrap the reinforcement. Place a sheet of roofing material at the bottom of the pit so that the soil does not absorb moisture from the concrete. Now the first layer of concrete (10-20 cm) can be poured into the pit. Immediately push the reinforcement into the pit with a roofing film put on it. When you fill in the first ten centimeters, start pouring earth around the column. It will prevent the concrete from flowing out from under the tube. Thus, fill the column to the top and move on to the next one. And so to the last. The main advantage of such a foundation is its low cost and significant time savings. You also need to pay attention to the absence of the need to use removable formwork, which significantly saves time. Due to the fact that the column is wrapped with roofing material, the soil does not freeze to it in the cold season and does not push it out - the roofing material simply slides. At the same time, a bag of cement will be enough for you for 5-8 columns. But in terms of strength, it is still inferior to a solid concrete slab, so it is not suitable for large and heavy buildings. Now nothing will stop you from starting the construction of a new house on your own and finishing it as soon as possible. And it's no longer necessary to hire an expensive team of builders for a job that you can actually do yourself.

The article describes the features of solid slab foundations. The scope of their application, operational and design differences are considered in great detail. Applied issues related to the construction technology of foundation slabs are brought to the fore.

This is a continuation of a series of articles about foundations, and we have already managed to publish a lot of interesting material. Therefore, we recommend:

A slab foundation, also known as “solid”, or “floating”, or “Swedish, Scandinavian slab”, is a solid slab located under the entire area of ​​\u200b\u200bthe building, buried in the ground, or laid on it. There are several design options for slabs - box-shaped, flat, ribbed, prefabricated from road reinforced concrete products, monolithic, with extensions at the corners, with or without reinforcement, insulated and cold ... All of them have their own distinctive features and a specific scope. For private suburban construction, in terms of economic and functional characteristics, flat monolithic reinforced concrete slabs with a thickness of 20 to 40 cm with insulation have proven themselves in the best way. We will talk about them further.

Why choose a slab foundation

In low-rise construction, which is what we are actually interested in, this type of foundation for many reasons will be preferable to its competitors (both tape and pile structures). This is explained by the advantages, both of a purely technical and near-construction nature.

Strengths of solid foundations

Universality in the geology of foundations. The floating structure can be correctly applied on all types of soils, including weakly bearing, heaving, horizontally mobile, with a high level of groundwater, permafrost…

There are some restrictions on the relief - it is difficult to build such a foundation on a slope, most likely, piles will be preferable. However, there are technologies proven by the Americans for erecting slabs on hillocks, which in their design (at the bottom of the site) have elements of high monolithic belts. Another “centaur” suitable for such places is a pile foundation with a low grillage in the form of a monolithic slab.

Good bearing capacity. This quality is due to the specific mechanics of the "house / slab / soil" interaction. In the next chapter, we will take a closer look at this point. Briefly - the plate has a large area of ​​​​support, so the pressure on the base soil is very low (from 0.1 kgf / cm 2). Therefore, a two-story stone house on a slab can be safely erected. They say that the elevator shaft of the Ostankino Tower stands on a monolithic slab.

High spatial rigidity. It is due to the absence of seams and joints, the use of rigid reinforcement, the massiveness of the structure and the high material consumption. The slab foundation is great for houses with "inelastic" walls, which are very afraid of even the smallest (1-3 mm) movements of the supporting structure - brick, aerated concrete, cinder block, shell rock and other mineral materials.

In the presence of excessively heaving soils and significant sensitivity of buildings to uneven deformations, it is recommended to build them on shallow and non-buried monolithic reinforced concrete slabs, under which pillows of non-heaving materials are arranged.

SP 50-101-2004 "Design and installation of bases and foundations of buildings and structures."

Good insulating characteristics. With proper execution, it does not let water through, prevents heat loss through the floor.

Simple construction technology, built quickly. Easy to mark, minimum excavation, simplified formwork design, easy to reinforce and concrete. Can be made by builders with low qualifications.

Conditional disadvantages of the slab foundation

It is technically very difficult to combine a solid slab and a basement in a structure.

It is possible to pour the slab only in favorable weather (it loses a little to prefabricated and pile driven foundations).

High price. Increased material consumption (concrete, reinforcement), of course, leaves its mark. But if you look at the problem as a whole, then the picture changes dramatically - we save a lot on other materials, construction stages, production operations:

• the slab becomes the rough floor of the first floor - no need to make an overlap;
• in the mass of the slab, you can lay a water heated floor, and not pour a separate screed for it;
• for the manufacture and fastening of formwork panels, less boards or sheet materials are needed (at least twice as compared to strip structures);
• no need to pay for the removal / planning of a large volume of selected soil;
• the height of the outer walls is reduced, since a lower plinth can be obtained (and these are expensive facade finishing materials, labor costs ...);
• lifting equipment, concrete pumps, excavators, driving headframes, drilling machines are not needed, everything is limited to mixer cars;
• you can build on your own and not hire highly paid professional builders, there is less risk of financially suffering from the "human factor" (simpler technology).

It turns out that the main drawback of slab foundations is the low awareness of the domestic developer about their advantages. But in the northern part of the United States and Scandinavian countries, monolithic slabs have become the foundation No. 1.

The principle of operation of the slab foundation

Situation

Building density is growing, people increasingly have to build on “bad” soils (weak, constantly wet, heaving, frozen ...).

Modern projects of country houses have become much more complex in terms of architectural and planning solutions: different parts of the building are built at different heights (one and a half floors, attached garages, special solutions for flights of stairs and landings ...), uneven distribution of load-bearing walls over the building area. Houses are now bigger, taller, heavier.

Problem

On top of the foundation and on the natural foundation, there are uneven effects from the house. From below, complex soils either tend to form local dips under the building, or push the building out with the forces of frost heaving, and then, thawing, sink. There is a danger of deformation and destruction of load-bearing structures.

Solution

Increase the footprint of the foundation, reducing the load from the house on a natural foundation.

To maximize the spatial rigidity of the foundation, to evenly redistribute the pressure “from top to bottom”.

With a heat insulator, separate the heated premises from the ground under the house - thus, eliminate the uneven freezing under the building (in winter, the ground under the stove does not thaw).

All these methods of dealing with “irregularities” are based on the principle of operation of an insulated monolithic slab. This is a kind of single platform under the house, which is not subject to local bends (with proper design), and without deformation is able to actually move along with the ground - “float”.

Design features of the slab foundation

The design of slabs differs significantly from the methods of developing other types of foundations. Here, engineers also take into account all the main soil parameters and all loads (mass of structures, operating weight, snow pressure). SP 20.13330.2011 has not been canceled.

However, the slab foundation must be considered as a single, jointly working “slab-above-foundation” structure. Therefore, in this case, special attention is paid to a detailed study of specific components of the building and the supporting structure as a whole, drawings of the house are created and calculated, indicating diagrams of the distribution of loads, their direction.

The whole problem lies in the complexity of competently modeling bending loads, possible rolls that the slab experiences, and, accordingly, calculate its thickness, configuration, and the need for reinforcement, including local reinforcement. The most efficient design of foundation slabs is carried out using special computer systems that produce very detailed working drawings. That is why we recommend ordering the calculation of the foundation slab in a specialized organization, the cost of such work will be from 5 to 10 thousand rubles.

The most widespread are slabs with a thickness of 20 to 40 cm, while one detail is very interesting: most calculations show that different slab thicknesses can be used for the same house, if the percentage of reinforcement is correctly manipulated.

For example, a solid foundation for some abstract building. At 20 centimeters - it is necessary to make local “additional reinforcement” of especially loaded zones and not make mistakes in the calculations, at 25 centimeters - the frame can be knitted evenly, without much risk. But a 30-centimeter slab, when compared with a 25-cm structure, will not allow saving on reinforcement, but much more concrete will go to it.

An exceptionally competent calculation allows casting plates even with a thickness of 15–18 cm.

Note that it is possible to significantly increase the resistance of the slab to punching, while reducing its total thickness (read material consumption) by making local thickenings of the foundation in the area of ​​\u200b\u200bthe corners, the junction of the bearing walls, along the entire perimeter, under the columns. Such reinforced slabs are often called "American", in cross section they look like a prism.

The slab foundation cannot be smaller than the house in area; all cantilever sections must be taken into account. For example, if the building will be faced with brick or other heavy materials, then the slab must be laid in large sizes to provide a supporting area for the cladding.

Slab foundation construction technology

Since slab foundations are often used in very difficult geological conditions, the most stringent requirements are imposed on the planning and construction of floating structures, which are stipulated by many regulatory documents, for example, SNiP 3.03.01-87 "Bearing and enclosing structures" or SP 50-101- 2004 "Design and installation of bases and foundations of buildings and structures." Naturally, only high-quality materials should be used for the construction of foundation slabs.

The construction of all solid foundations is carried out approximately according to the same scheme:

• Design.
• Marking (only the contours of the building are taken out in kind).
• Sod removal, soil sampling (if cushion / drainage is needed).
• Laying of buried communications (water, sewerage).
• Pillow, drainage device.
• Installation of hydro and thermal insulation.
• Assembly of "warm floor".
• Knitting and laying of the reinforcing cage.
• Assembling and fixing the formwork.
• Concreting.
• Stripping.

Let's look at these operations in more detail.

We have more or less figured out the design. Build something serious - it is better to order the development of a foundation project to engineers, definitely save your nerves and money.

We have already discussed the issues of preparatory work, the removal of markings in nature in the article “Strip Foundation. Part 2: preparation, marking, excavation, formwork, reinforcement.

As for earthworks. If replacement of the soil (massive pillows) and insulation is not required, then it is enough to remove only the upper fertile layer, otherwise, the natural base soil is removed in the required volume. Sometimes, before excavation, it makes sense to level the building area - to make backfill. Then the additional material is very carefully compacted with a vibrating plate.

The most important condition is that the bulk soil under the slab foundation should not be inferior to the mainland (natural) in any way.

Do not worry about the fact that it will be difficult to maintain communications under the stove. Everything is done as usual: where there will be a technical room, a pit is always made in the slab for the input of communications (foam plastic is laid near the pipes, or a contour is made from the formwork), the smaller it is, the better for the rigidity of the foundation. In any case, the pipes cannot be monolithic tightly. Under the slab, communications pass in a trench, covered with drainage materials. Read about the drainage of communication lines in the article "How to make drainage on the site."

The pillow is an artificial base, it is designed to replace "bad" soils. The most common material for the pillow is a mixture of sand and gravel, which have good drainage properties, shrink a little, and do not swell. The sand and gravel cushion is laid in layers of 100 mm, and each cake is carefully rammed with a vibrating platform. If clean sand is used, then it must be spilled with water.

It is necessary to periodically check the horizontality of each layer of pillows.

In areas with an unfavorable water balance, it is recommended to lay several drains under the slab (cushion) to drain water.

Most of the technological maps for the manufacture of solid foundations suggest laying geotextiles under the pillow, which does not allow sand and gravel to silt (read, lose important properties for us).

In order for the hydro- and thermal insulation to lie well and not be deformed by the mass of concrete, the upper part of the pillow must have the most even plane. Some manufacturers of floating foundations even prefer to make a sand concrete screed preparation.

The pillow is covered with a dense polyethylene film, or other waterproofing materials that, during concreting, will prevent leakage of cement laitance. The sheets are overlapped and glued/soldered.

A layer of insulation up to 100 mm thick is laid on the waterproofing. Previously, foam was used, now everyone has switched to extruded polystyrene foam. Some builders believe that insulation is not an obligatory layer, but it reduces heat loss through the slab, does not allow the soil under the slab to uncontrollably, unevenly thaw even under heated rooms. If you want to use a warm floor, then you will not heat the ground, but let all the heat into the house. In the technological maps of foreign companies, insulation (and a pillow) is recommended to be laid outside the slab.

Underfloor heating pipes are laid out directly on XPS sheets using a special mesh, of course, they are not insulated with any materials in order to better give off heat. Some heating routes can also pass in this layer - here they are in sleeves and heat insulators. All ends are taken out of the pit for communications, the system is ringed, pressed. Under pressure, the air pumped into the pipes prevents them from deforming when pouring concrete.

Reinforcement is perhaps the most difficult operation in the construction of floating foundations. This is where most errors, both technological and design, are made.

Let's start with the main one. According to SP 52–103–2007, the minimum percentage of reinforcement of a reinforced concrete slab is 0.3%. It is calculated as follows: they take a cross section of the slab and calculate its area, calculate the total area of ​​the cut of all reinforcing bars, compare these indicators. If the metal content of concrete is insufficient, then increase the diameter of the reinforcement or the number of rods (reduce the pitch). For thick slabs, a third tier of metal is used, located in the thickness of the slab. Practice shows that most often it is enough to lay two layers of reinforcement with a diameter of 12–14 mm and a step of 150–250 mm.

Do not forget that in loaded areas (columns, a load-bearing wall inside the building ...) additional reinforcement may be required, carried out by laying auxiliary longitudinal rods within the punching prisms.

Depending on the design of the building under load-bearing walls and columns, it sometimes makes sense to make vertical releases of reinforcement (SP 52–103–2007), which will provide additional rigidity to the “slab-above-foundation part” system.

The presence of a protective layer of concrete is a prerequisite for high-quality reinforcement. Reinforcing cage meshes are placed on special polymer mushroom stands. The fungi of the lower tier are small, about 4–5 cm. The intermediate fungi (between two grids) have a height depending on the thickness of the slab, so that about 5 cm of concrete remains above the upper reinforcement (protective layer). The fungi are placed one above the other, their total number (step) must ensure sufficient resistance of the frame to the loads arising during concreting.

It is forbidden to use all kinds of linings made of wood, stone, metal.

The ends of the frame, the upper and lower tiers, are recommended (SP 63.13330.2012) to be connected to each other with U-shaped reinforcement elements. Reinforcing bars should not come into contact with the formwork, as a protective layer of concrete with a thickness of at least 40 mm should be provided.

The frame is made with viscous reinforcing bars with wire. It is allowed to use electric arc welding, but then it is necessary to use fittings of class a500s, or similar, with index "C".

Due to the large amount of reinforcement work, it is advisable to use unified prefabricated welded meshes. The joints obtained after laying are necessarily bred in a “chessboard” order - the joints of the finished meshes of the lower tier of reinforcement must be overlapped by a whole mesh of the upper tier.

The formwork of the floating foundation is very easy to assemble, it is only necessary to align each side of the perimeter. Please note that a lot of concrete is used, and the pressure on the shields will be quite serious - so spread them very well from the ground.

The formwork should be wrapped with polyethylene from the inside to prevent leakage of cement laitance through the cracks. Alternatively, it is possible to lay XPS sheets near the formwork, then they will reliably “stick” to the concrete and provide vertical insulation of the slab.

Expanded polystyrene is also separated by buildings associated with the house, which require their own foundation (garage, porch, terrace ...).

A separate small formwork circuit is made for a pit for communications.

You can read about formwork and reinforcement in the article “Strip foundation. Part 2: preparation, marking, excavation, formwork, reinforcement.

The nuances of manufacturing a monolith can be found in our publication “Strip Foundation. Part 3: concreting, final operations.

Concreting must be done in one work shift. It would be most rational to order the delivery of concrete with a mixer and pour the foundation directly from the tray. For concreting remote areas, you can use a homemade chute.

Concrete must be compacted without fail with a deep vibrator.

For the manufacture of slab foundations, concrete is used with characteristics that are regulated by SP 52-103-2007. Most construction companies producing floating foundations offer to order concrete with the following performance properties:

• strength class from B22.5 (grade not lower than M300);
• water resistance coefficient from W8;
• frost resistance from F200;
• mobility P-3;
• possibly sulfate-resistant if the water table is high.

Taking into account domestic realities, it is better for a private developer to order concrete, at least a grade higher than the standard one - there will be more chances to get the design strength class.

The next step is to take care of the concrete. When the slab gains 50% strength, the formwork can be removed. We examined these works in detail in the article “Strip Foundation. Part 3: concreting, final operations”, we add that the next day after pouring the floating foundation, the upper plane of the slab should be rubbed - this will be a good base before installing any floor coverings.

In Northern Europe and the USA, floating foundations have been actively used for more than half a century; they have proven their reliability, functionality and economic attractiveness over time. In our country, the plates also found their developer. From year to year, solid foundations are becoming more popular, since in many cases there is simply no alternative to them.

Turishchev Anton, rmnt.ru

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