We make a slab foundation with our own hands. Recommendations for pouring and reinforcing a monolithic slab. How to make a slab foundation: step by step instructions Correct monolithic slab

Usually, the foundation for the future house is chosen very carefully. At the moment, the most reliable is considered to be a monolithic slab in the form of a foundation. It is suitable for any kind of building, but is mainly suitable for heavy buildings. It is worth considering that its cost is quite high, so it is not always correct to install the stove. In this article, we will consider the characteristics that the foundation slab has, as well as the cases when it will be appropriate during construction.

Advantages of using reinforced concrete slabs for the foundation

A monolithic foundation slab is a shallow or floating foundation. It is called so because after it is poured, a large slab is formed under the entire area of ​​\u200b\u200bthe house.

Be sure to organize a sand and gravel cushion before pouring the slab, which will become a transitional element between the foundation and the ground, allowing you to properly distribute the load from the building. Such a foundation is indispensable for construction on soils with a large freezing depth, as well as on unstable soils. In addition, this is the best option for an aerated concrete house due to its quality characteristics.

Important! You can save time and money by not ordering heavy equipment for the delivery of slabs, but pouring it on the spot yourself.

A monolithic slab can be easily equipped with your own hands, without involving professionals in the work. Pouring of concrete can be carried out directly from the concrete mixer. If you do all the work on the technology, then you can do everything yourself.

In addition to ease of installation, there are also several other advantages of the foundation slab:

• Since the foundation is equipped with a height between 15 and 40 cm, the work of digging a pit is reduced.
• The fill volume is also reduced by 1/3.
• The arrangement of the foundation will take noticeably less time due to the ease of installation.

The above characteristics apply to a shallow or non-buried slab foundation, but a monolithic slab for arranging a basement or basement will be more costly than known foundation technologies. If you plan to build a house with a basement on shaky ground, then you can’t do without a slab foundation, it will become the floor for the lower floor. However, the cost, which can be even 50% of the entire budget, quickly pays off with high reliability and durability, as well as long-term operation, subject to proper installation.

A frost-resistant monolithic foundation, which is very common in Scandinavian countries, is used as a foundation on soils that have a very low freezing point. The thermal insulation effect is achieved by insulating the foundation slab.

Types of foundation slabs

All slab foundations can be divided into three types:

Requirements for materials for a monolithic foundation

To create any type of foundation, you need to use only the highest quality materials. The main thing in this list is concrete, which, according to the standard, must meet the following indicators:

• The water resistance coefficient must not be lower than W8
• According to the strength class, the concrete grade must be at least M300
• According to the mobility coefficient, a material with an index of P-3 will suffice
• In terms of frost resistance from F-200.

Important! For areas with high water tables, sulfate-resistant concrete is best.

Also, be sure to pay attention to the choice of reinforcement for the slab foundation. If it is planned to traditionally reinforce the foundation slab by tying reinforcement, then any type of reinforcement can be used. If it will be welded with other parts, then it is more expedient to choose the class of reinforcing steel A500C with a diameter of at least 12 mm. Such steel is used just for welding.

For waterproofing, polymer-type bituminous materials in rolls are most often used. You can also choose some other material, since now the construction market is ready to offer customers a lot of various waterproofing materials with characteristics that are suitable in each case. They are distinguished by a more favorable composition, which allows the material not to freeze in winter and not to melt during the summer heat.

It is also worth mentioning the insulating materials, which can also be used when installing the foundation slab. Previously, it was just ordinary polystyrene, but now a material called polystyrene foam has been developed, which is of high quality, strength, durability and is completely resistant to decay.

It is used for the manufacture of a heat-insulating pad under the foundation and for the insulation of the outer walls of the basement and basement during the installation of an insulated Swedish plate using underfloor heating technology.

Do-it-yourself foundation slab device

Before work, you need to prepare all the materials and tools that will be required during work, so that in the future you will not be distracted by their search. This list includes concrete mix, rebar, concrete leveling slats, formwork boards, hammer, level, line for marking, shovels and bayonet-type shovels, an ax, hacksaws, consumables, wire and a crochet hook for rebar.

Be sure to take care of renting heavy equipment for digging a pit if a deep foundation is being installed.

Slab foundation installation technology

The first and decisive step during installation is the exact calculation of the foundation slab and the bearing capacity of the soil, as well as the loads on the foundation. At this stage, the risk of deformation, roll and shrinkage of the foundation is necessarily calculated. Already, according to all these indicators, it is determined how the foundation will be laid. This stage is best entrusted to professionals, because independent study and calculations can give the wrong result.

The next step is earthworks to dig a pit and lay geotextile materials on its bottom to prevent mixing of the sand cushion with the underlying soil.

After you need to fill up the gravel-sand pillow in layers. Sand is best for a tighter fit to lay immediately wet. Each layer of material of 10 cm must be treated with a vibrating plate. If a Swedish insulated plate is installed, then engineering communications are introduced at the same stage.

After all the actions taken, the concrete solution is poured. With a conventional monolithic foundation, before this step, a reinforced mesh is laid on a sand cushion in the formwork.

Important! Concrete must be poured at one time and treated with a deep vibrator to ensure that there are no layers and voids inside.

To install the Swedish slab, you need to make a preparatory layer of concrete on top of the foundation pad 10 cm thick. After hardening, a waterproofing material is laid on the base, which is 30 - 50 cm larger than the future foundation and soldered with a burner at the edges. Extruded polystyrene foam is laid on top, a polyethylene film is laid on top of it. The resulting base is laid with a reinforcing mesh and a formwork is arranged around the perimeter, into which high-grade concrete is poured. Thus, the technology of a warm floor is obtained.

The finished foundation dries out in about a month. The time for building a fortress depends on the air temperature at which the foundation will dry. This relationship is shown in the table below.

While this process is going on, you need to wet its surface with water several times a day, especially on hot days. You also need to cover it with polyethylene so that precipitation and various kinds of debris do not fall on the surface.

Conclusion

Foundation slabs in some cases are the most successful foundation option. There are several types of monolithic foundations, which differ from each other in terms of quality and cost. Among them, you can find exactly the one that is suitable for certain conditions. But the choice, as well as the construction of the foundation, is not an easy task, therefore, for those who do not have any experience in this matter, it is better to rely on the opinion of specialists.

In our time, when the field of building materials is rapidly developing, there are many types of foundations that differ in characteristics, type and purpose. But recently, among professional developers, the slab foundation has become more and more in demand. This type is especially convenient for owners of plots with land in poor condition. And also, this option is considered one of the available. Even an inexperienced person in repair matters can pour the foundation slab on their own, without putting much effort.

Areas suitable for slab foundation applications

The most important feature of the slab foundation is a shallow base, which is made of a concrete cushion. This property allows you to fulfill its purpose even on moving soils. Any other type of foundation will be covered with cracks during the movement of soils, therefore, in such areas it is necessary to use exclusively slab foundations.

This base is perfect for building houses where hard materials are used. It prevents deformation of the structure.

Buildings that have low, in comparison with the ground, floors, must be erected using exclusively slab foundations. When using it, there is no need to build a basement and grillage.

Slab foundation advantages and disadvantages

Before you start choosing a particular product, you need to weigh all its pros and cons. Let's start with the positive qualities of the slab foundation:

• It is reliable and durable. And it's hard to argue with that. Interview specialists who are versed in building materials, and all of them will say that tiled is the most reliable type of foundation.
• It has a large area of ​​\u200b\u200bsupport on the ground, and if it is laid correctly, the soil will not adversely affect the foundation in the cold season.
• The slab foundation is universal. The fact is that the technical characteristics that it possesses allow it to be laid on almost any soil. Therefore, this type is most often used in areas where no other foundation could cope with the task.
• The ability to establish a foundation above the depth of freezing of the earth. This plus was made possible thanks to the massive sand and gravel cushion, which prevents the impact of the soil in the cold winter.
• A high level of rigidity, which prevents the house from sagging, and if this happens, then the room will not be significantly damaged.
• No need to install a subfloor.
• The ease of device technology, which allows you to do the work on your own and save on the services of a master.
• Suitable for any type of low-rise building. The only thing to consider is the thickness of the slab (the lighter the room, the thinner the slab).
• Can withstand ground movement. It is possible to build a house on floating lands, since the tiled foundation will not burst and tear, but will simply begin to move along with them. This property is to keep the building intact.

It should be borne in mind that all the previously listed advantages will be valid only if the installation rules are strictly observed. If there are violations of technology during the laying process, then the pros can turn into cons.

As with any foundation, there are some negative qualities:

• One of the biggest downsides that buyers point out is the price. The high cost is justified by the large amount of concrete, reinforcement, sand, and crushed stone, unlike analogues. But on the other hand, the money spent quickly pays off. The tiled foundation will not need frequent repairs, expensive maintenance, moreover, it will function as the floors of the first floor, which will also reduce costs.
• It is not recommended to lay a tiled foundation under the house, which is located on a site with a large slope. In this case, the output will be leveling the ground level, or installing a basement, but this is quite an expensive pleasure.
• There are difficulties with the construction of the basement. In the case of building a basement, you will have to fill in a monolithic slab under it, which will cause significant losses to the owner.
• The occurrence of difficulties during the installation of the foundation in winter days. To pour concrete in sub-zero temperatures, you will need to spend money on heating it and maintaining the warmth around it.
• Difficulties in wiring communications. Consideration should be given to the location of plumbing, electricity, etc. before the start of pouring concrete because after that it will be impossible to do this.

As you can see, the slab foundation has a large number of advantages, and the disadvantages can be circumvented, however, this will cost additional costs.

Material calculation

Before starting work, it is necessary to calculate the slab foundation: the dimensions of the formwork, the number and diameter of the reinforcement, the volume of concrete. All these values ​​can be found using a special calculator. To do this, you will need to enter the brand of concrete, the width and length of the slab (in meters) and its height (in cm). Further, the program itself will calculate the amount of materials necessary for arranging the foundation.

Types of slab base

Also, before starting work, it is worth deciding on the type of tiled base. There are several options. The main ones are:

• ordinary concrete pad;
• tape-slab.

This type is used during the construction of buildings with a basement. A hole is dug, a concrete pad is placed, on which the base is subsequently installed. The entire load is placed on the strip foundation.

• base with stiffeners;

It is the best option among all, because it has high strength. Its construction requires more materials and effort, so its technical characteristics are superior to other types of foundations.

Preparation of materials and tools

Preparatory work also includes the assembly of a set of materials:

• concrete;
• steel bars;
• gravel;
• sand;
• material for waterproofing (geotextiles are most often used).

You will also need some tools for the slab foundation:

• saw;
• a hammer;
• shovels;
• transport wheelbarrow;
• apparatus for welding;
• Bulgarian;
• roulette.

Construction of a slab foundation

Instructions for the construction of a slab foundation includes several steps:

1. First of all, we carry out a geological study of the earth, determine places with strong elevation changes.

2. We mark the future base.

3. We remove the soil layer and level the area where the construction will be carried out.

The choice of the depth of the pit directly depends on the type of structure (shallow or swollen). If we consider a shallow foundation, then it will be enough to remove 50-70 cm of earth. The dimensions of the pit are selected taking into account that they should be 1-2 meters more than the length / width of the foundation. After digging, be sure to compact the soil.

4. We design and install formwork (strong wooden boards are suitable for its construction).

5. We dig several trenches in the pit and lay waterproofing in them.

6. We lay plastic pipes on top of the waterproofing.

7. We fill the bottom with a mixture of sand and gravel, evenly distribute it and tamp.

8. We assemble a double reinforcement cage and tie it with a special wire.

For reinforcement, only rods with ribs are suitable. They will provide high-quality adhesion of the frame and concrete mix, as well as prevent stretching of the foundation slab. Using smooth rods in the work, the base will crack at the first subsidence of the soil. The reinforcement is laid in increments of less than 30 cm. If you increase the distance, then the strength of the base will decrease significantly.

9. We put plastic pipes in places where various communications will be located.

Before installing them, it is necessary to fill them with sand and carefully compact the backfill. Pipes must be laid before pouring, since it is forbidden to make holes in concrete.

10. Fill the monolithic slab with concrete mortar.

The slab foundation is poured immediately. The concrete solution must be kneaded once and a large amount, so that it is enough for the entire pour. The work is quite laborious, so ideally it should be done by four people. We lay the concrete in uniform, horizontal layers. It is necessary to fill in such a way that the plate does not have deviations from the horizon. To prevent such slopes, we create stiffeners in the lower part. These are strips of concrete, made in the shape of a trapezoid. The last layer must be poured very quickly. Use a mixer or concrete pump for this.

11. Carefully smooth and level the surface.

12. We cover the resulting foundation with a film and leave it for a couple of weeks. Do not forget to moisten the construction during the first five days.

How to mix concrete for the foundation?

To reduce the cost of work, you can knead concrete at the site of the foundation with your own efforts. But in this case, you will need a special concrete mixer. It perfectly mixes all the components without forming lumps. This unit operates at a power of 250 watts or more. At one time, you can get from 50 to 250 liters of solution. But the quantity greatly affects the time of work. If we take a small device as an example, then it will take about 5 hours to create 1 pour cube.

An important point is the location of the concrete mixer, it should be located near the base. This will reduce the amount of force you apply.

Of course, there is an option to independently knead concrete for a slab foundation using a shovel, but this will greatly affect the quality of the future foundation.

Warming

Of course, the best option would be to insulate the foundation to achieve a warm indoor temperature all year round. To do this, use various heaters. The most popular among them is foam. Only 10 cm layer will be enough.

Also, there are different types of insulation. We recommend using the subfundamental. Insulating material is placed directly under the stove.

Use the tips below to make your job easier:

1. To create a quality foundation, you need to use only durable reinforcement and concrete mix.

2. The use of a shallow base will reduce the cost of building materials by approximately 35-45% of the cost of an underground room.

3. It is very important to consider the thickness of the slab. For example, choosing a base thickness of 20 cm, you will need to "reinforce" in some places where there is too much load. At 25 cm, it becomes possible to knit a frame of reinforcement uniformly, without resorting to additional reinforcements. A 30-centimeter thickness will help increase the strength and durability of the foundation, but at the same time it will make you spend a lot on concrete.

4. During the manufacture of a cushion of sand and gravel, the material must be laid in layers. One layer should not exceed 12 cm. After each masonry, carefully tamp. If your pillow will consist entirely of sand, be sure to moisten the layers.

5. Before laying the insulation material, the pillow must be covered with a dense polyethylene film to prevent water leakage from the concrete solution. It is advisable to glue or solder the polyethylene at the joints, or overlap the sheets.

After reading this article, everyone will be able to make sure that the construction of a slab foundation is a fairly simple process and is possible when creating it yourself. The main thing is to follow all the rules of pouring and construction technology. If this is done, then your foundation will serve faithfully for many years.

Also, we suggest watching a step-by-step instruction on how to properly build a slab foundation. The video is located after the article.

Among all the types of foundations chosen by private developers for the construction of their country houses and outbuildings, the bases are the undisputed leader in terms of frequency of use. However, quite often the specifics of soils at the construction site, the climate in the region, the location and dynamics of changes in underground aquifers require an excessively deep laying of the sole of the strip foundation, which makes it an unprofitable solution, especially when it comes to building a relatively small in size and total mass building. We have to look for other, more economically justified, but at the same time options that are not inferior in terms of bearing capabilities.

One such solution can be a monolithic slab, poured under the entire future building. The uniform distribution of the load falling on such a foundation over the entire considerable area makes it possible to use such a scheme on soils with a low bearing capacity. And the comparative simplicity of the construction of such a foundation makes it quite feasible on our own. So, the topic of this publication is the foundation slab with your own hands, a step-by-step instruction, from calculations to practical implementation.

General information about the foundation - a monolithic slab

Typical scheme of a monolithic slab foundation

A slab foundation does not require a deep occurrence, rather, on the contrary, its bearing capacity and “floating” features will appear precisely when it is close enough to the ground surface. In this case, even frosty swelling of the soil will not have a destructive effect on the stability of the building - the slab itself, with its high-quality construction, together with the building erected on it, seems to “float” on the surface of the soil.

The schematic diagram of the device of a monolithic foundation slab is shown in the illustration below:

1 - Compacted soil - the bottom of a pit dug under the foundation.

2 - A carefully compacted "pillow" of sand, sand and gravel, gravel, which contributes to an even distribution of loads, becomes a kind of damper that softens the impact of ground vibrations. Layer-by-layer backfilling and tamping of such a “cushion” is practiced, with one or another alternation of materials, or homogeneous, using ASG.

3 - A layer of geotextile (dornite), which will give the sandy "cushion" a kind of "reinforcement", prevent it from silting or blurring on waterlogged soils. This illustration shows only one of the options for placing a geotextile layer, however, their number and position may vary, depending on specific conditions. So, often such a layer is placed between the surface of the compacted bottom of the pit and the first layer of sandy "cushion" - to prevent the penetration of soil particles into it. A layer of geotextile also separates the sand and gravel layers of the backfill - again for reasons of reinforcement and exclusion of interpenetration. At the same time, the location of the gravel or crushed stone layer above the sandy one seems to be more optimal - because the capillary "suction" of ground moisture from below is almost completely excluded.

4 - A layer of so-called concrete preparation. This element of the general "pie" of the slab foundation is often neglected for reasons of saving material and reducing the overall duration of the work. Meanwhile, such concrete preparation plays a significant role - it allows you to reach the “clear geometry” of the base for further pouring the foundation or laying insulation materials, it makes it possible to mount the hermetic waterproofing, which is mandatory for the slab, with high quality.

5 - The already mentioned layer of a waterproofing layer that is mandatory for such a foundation slab, protecting the base of the building from moisture from below. The optimal solution is at least two layers of polymer-bitumen-based roll waterproofing materials.

6 - The monolithic slab itself with the calculated thickness.

7 - reinforcing belt of a concrete slab. Its classic design is two levels of reinforcing bars interconnected to give volume to the structure with special clamps. The location of the reinforcement is planned in such a way that a concrete layer of about 50 mm is created between the bars and the edges of the slab from above, below and from the ends - in order to exclude the start of metal corrosion processes.

This is a general scheme, but there are several varieties of monolithic foundation slabs used depending on certain specific construction features.

The simplest and probably the most common option is a solid slab, the uniform thickness of which is observed over its entire area.

Prices for PGS

It is this scheme that is most often chosen when erecting houses and outbuildings on fairly stable soil. However, it has an obvious drawback - the thickness of the slab is usually small, and it is partially located below the ground level, that is, the upper edge is located close to the surface of the earth, which is not very good for wall structures. It is not economically feasible to increase the thickness of the slab because of this, which means that another option can be considered - pouring the foundation with reinforcing stiffeners, which have some similarities with the strip foundation. Moreover, these ribs can be located both above the plate and below it.

So, a kind of socle-grillage can be obtained if, simultaneously with the slab, stiffening ribs protruding above the surface of the slab, which is obtained as a “bowl”, are also poured. Such grillages are placed along the lines of the construction of the load-bearing walls of the house structure - after waterproofing their horizontal surfaces, it is from here that the masonry begins.

A similar scheme is often practiced in cases where the useful use of the basement or basement floor is planned - the slab simultaneously becomes the floor of these premises. And from the grillages, at the same time, they begin to lay the basement.

If there is no desire to deepen the slab too deep into the ground, and at the same time achieve its maximum bearing capacity without thickening, you can apply a scheme in which the stiffeners are located facing down.

When preparing the surface, installing the formwork and reinforcing frame, recessed “channels” are immediately provided, which, after pouring the slab, will turn into stiffeners facing the ground.

This also turns out to be a kind of "symbiosis" of slab and strip foundations. Stiffeners are planned under the outer walls and capital internal partitions. Well, if there are no internal partitions, then the ribs should be parallel to each other and to the shorter side of the perimeter of the house, with a step not exceeding 3000 mm.

Such a scheme makes it possible to achieve serious savings in concrete, since with properly planned stiffening ribs, the thickness of the slab can be significantly reduced, by 100 ÷ 150 mm, without losing its bearing potential, and this is, after all, 1.0 ÷ 1.5 cubic meters of mortar for every 10 square meters area.

In addition, there are ample opportunities for warming the foundation slab - the same height difference on the main surface and on the stiffeners is often performed by laying a durable thermal insulation material, for example, extruded. By the way, it is this approach that is the key condition for the construction of one of the improved varieties of slab foundations - the so-called "insulated Swedish slab".

Insulated Swedish stove (USHP) - the basis for houses with minimal energy consumption

The tendency to build houses with minimal, zero or even negative external energy consumption, widely used in modern world construction, leads to the emergence and development of innovative technologies, which include UWB. The main nuances are discussed in detail in the corresponding publication of our portal.

It makes sense to make one more remark. Slab foundations can be not only completely poured, monolithic, but also prefabricated, consisting of ready-made reinforced concrete structures laid close to each other. It would seem that this is much simpler, however, the lack of a rigid connection between adjacent plates makes such a base unstable to possible ground vibrations. For this reason, such a scheme is not widely used, and in residential private construction it is practically not used. An exception can only be small-sized outbuildings, the area of ​​\u200b\u200bwhich is limited by the size of one standard slab, but this, you know, is extremely rare.

Application of slab foundation. Its main advantages and disadvantages

The use of a slab foundation will be fully justified in construction sites that are characterized by soils with reduced bearing capacity. It is usually resorted to where simpler schemes, such as a shallow belt or columnar, are simply impossible due to the peculiarities of "geology": the tendency of soils to frost heaving, horizontal "shifts", close location of aquifers, etc.

In addition, such a foundation, with careful calculations and design, can become a very reliable basis for multi-storey construction. Uniform distribution of loads over a large area of ​​​​the base gives very small indicators of pressure on the ground, even during the construction of massive buildings and engineering structures. True, this applies to a greater extent to construction work carried out on an industrial scale.

About the advantages and disadvantages of the slab foundation, by the way, both real and, frankly, far-fetched, there is a lot of controversy. Let's try to list them and understand a little about this issue.

What they say about virtues ?

• There is a widespread opinion that a monolithic slab foundation is an absolute "panacea" for all cases, that is, it can be built on any soil at all. Allegedly, such a slab of a house, even in a swampy area, will be a reliable basis for a heavy building, since due to its “buoyancy” it will begin to oscillate along with the movements of the soil without being deformed.

It is certainly impossible to agree with such a statement. Most likely, it would be more correct to say only that the slab foundation opens up expanded possibilities for construction in areas with difficult soils, with insufficient bearing capacity for the tape base, with average heaving rates.

But on clearly swampy, waterlogged soils, with the likelihood of subsidence, especially in regions with a harsh winter climate, only a pile foundation will probably become a reliable foundation, for years the piles are driven (screwed) into dense, bearing rocks located significantly below the freezing level.

And the slab foundation, located practically on the surface, can indeed move within certain limits along with ground vibrations, that is, “float”. But the trouble is that in areas with pronounced soil instability, these vibrations can have a very high amplitude, and are applied unevenly to the surface of the slab from below. Even if the soil is absolutely homogeneous over the entire area, this unevenness is explained by banal reasons - on the south side, freezing almost always goes to a shallower depth, and thawing in spring occurs much faster. And this means that the plate willy-nilly will experience enormous internal bending stresses.

Prices for extruded polystyrene foam

extruded polystyrene foam

As a rule, slab foundations have a very significant margin of safety, and, perhaps, the slab itself will withstand such loads, it will not crack, but small linear deformations are quite likely. They will certainly be transferred to the walls, and in addition, the roll of the entire building from the vertical axis is not excluded. For wooden buildings, it may not be so critical, due to a certain mobility of the structure. But the stresses on rigid stone (block) walls increase with height, that is, with the lever of force application. And it is possible that somewhere in the upper region of the wall a crack will suddenly appear and begin to expand.

So, if you think objectively, you should not overestimate the versatility of the slab foundation - it would be reckless. In any case, if there is no certainty of unconditional success, it would be more expedient to invite specialists to conduct a geological analysis of the site. In addition, it is always useful to get acquainted with the “history” of the use of slab foundations in the surrounding area - what and how long the houses were built on them, what is the depth of the foundation and the thickness of the slab, are there any complaints about the operation, how did the buildings survive seasonal ground fluctuations - these and other questions help you make the right choice.

• Slab monolithic foundations make it possible to build large, even multi-level houses built from heavy materials.

This is true, and many high-rise buildings in large cities are on a similar basis. In terms of its ability to evenly distribute the load over a large area, such a foundation has no equal. Of course, all this is true with professionally carried out calculations, taking into account the characteristics of the building site, and high-quality performance.

So the conventional wisdom that the slab foundation is suitable only for small compact houses, and that "its age is short" is limited to 35-50 years - this is nothing more than fiction. We repeat - everything depends on competent professional calculations and on the quality of execution in accordance with the project.

• The construction of a slab foundation minimizes the work of digging a pit - no deep penetration into the ground is required.

If we talk about a slab located on the surface of the soil or with a slight depth, then this is true - only the top fertile soil layer is removed, and the depth of the pit is largely determined by the estimated height of the sand and gravel cushion. True, if this depth is also multiplied by the entire area (and the slab must be laid wider than the future building, and even plus insulated blind areas), then the volume of the selected soil can still turn out to be considerable. So this advantage is very non-obvious - with a shallow strip foundation, sometimes it is simpler in this regard.

Well, if you plan to use a deep monolithic slab, that is, to create a house with a full-fledged basement on its basis, then you will have to dig the appropriate pit, that is, it is very difficult to do without the involvement of special equipment.

• The use of a slab foundation automatically solves the problem of a reliable foundation for the floors of the first (or basement) floor.

This is a really important advantage. And if, simultaneously with the preparation of the slab for pouring, a high-quality thermal insulation belt is provided, then the floors will also be pre-insulated. In the "insulated Swedish stove", in addition, the contours of water heating of the floors are immediately mounted.

• Work on the slab foundation can in no way be attributed to tasks of an increased category of complexity.

An ambiguous statement, with which, nevertheless, one can agree to a certain extent. Indeed, the work on the stove itself does not involve operations that require the highest qualifications of workers. Digging a pit and tamping a sand and gravel pad, knitting a reinforcing cage, installing formwork, pouring and distributing concrete, caring for a slab that is gaining strength and other steps - all this is either initially clear, or a novice master can “fill his hand” in a very short time.

Another thing is that a number of operations require the involvement of special tools and equipment. So, for high-quality ramming, one cannot do without a vibrating plate, for quick and uniform manufacture of reinforcing clamps, it will be necessary to build an appropriate device, waterproofing with rolled materials involves the use of a gas burner with a cylinder. And considering that the volume of poured concrete can turn out to be considerable, and it is desirable to pour the slab in one day, it is hardly worth relying on - you will have to order it with delivery.

It can be said that, provided that forces and means are attracted from outside for some operations, the owner, with the help of friends or relatives, can easily cope with the main amount of work. True, one must be prepared for the fact that the work ahead is quite lengthy, physically difficult, and sometimes also tiring and monotonous. But for a small combined team of several strong men - doable. Of course, with strict adherence to all technological recommendations.

Interestingly, in some publications on foundation slabs, this is presented not as an advantage, but as a disadvantage - they say, working on such a slab is an extremely difficult task. It is possible that it is simply a matter of different evaluation criteria - from what point of view this problem should be considered.

Now let's turn our attention to limitations slab foundation:

• It is quite obvious that this type of house foundation is suitable for building on a relatively flat area. If a significant difference in height is observed in the building spot, then such a scheme either becomes extremely complicated, becomes impractical, or is recognized as completely impossible.

• The slab must completely, with its entire area, rest on the ground - this is precisely its increased bearing capacity even on not quite stable soils. And this, in turn, means that there can be no question of any basement or cellar under the stove itself.

The only exception can be the scheme already mentioned above, in which the slab itself becomes the floor of a full-fledged basement, semi-basement or basement. It, as a rule, has stiffening ribs-grillages directed upwards, or well-thought-out reinforcing tabs, from which further construction of the buried part of the walls is already underway, by analogy with a deep-laid strip foundation. But this type of foundation is a very expensive "pleasure" that requires highly qualified calculations and practical implementation.

• The construction of a slab foundation will require advance planning and the laying of the necessary engineering communications, for example, water supply, and sometimes power cable.

It is unlikely that such requirements can be attributed to shortcomings - this is rather assessed only as a specific technological feature, and with well-planned work, it will not particularly complicate the entire construction process.

• There is a lot of talk about the high cost of such a foundation, which can reach almost half of the entire construction estimate.

Such frightening indicators, apparently, will be valid only for the deep-laid slab already mentioned above. If the foundation is practically not deepened, the picture is certainly not so “terrifying”.

Of course, even with a small thickness of the slab, but with its considerable total area, centimeters very quickly grow into cubic meters of concrete mortar. Two-tier reinforcement will require a significant consumption of reinforcement, of course, more than when pouring a strip base. However, we must not forget that, along with the foundation slab, the developer immediately receives a ready-made foundation - in fact, the draft floor of the first floor, with it already completed with high quality, and sometimes with insulation. That is, these stages of work already fall out of the total estimate.

So the excessively high cost is by no means always an obvious drawback, and the ease of construction of the slab also largely compensates for the increased consumption of building materials.

How is a monolithic slab foundation calculated

Any foundation requires calculations, and the slab foundation is no exception in this matter. True, it should be specifically noted that the design of such structures is still the lot of professionals, especially if it is planned to build a full-fledged country mansion.

However, sometimes you can resort to calculations on your own, for example, when building non-residential structures - a garage, a barn, a bathhouse, and utility buildings. And one of the key parameters of the calculation is always the thickness of the monolithic slab. Too small thickness may not be able to cope with bending loads, excessive thickening is an unnecessary expenditure of effort and money.

How is the optimal slab thickness calculated?

Calculations should ideally be preceded by an analysis of the soil on the development site, since it is necessary to have an idea in advance about the bearing capacity of the formation on which the foundation slab will rest. Usually, specialists with a drilling rig are invited for this, who make several pits, for example, in the corners and in the center of the site.

This makes it possible to estimate the composition and thickness of the layers, the presence of a "perch water", the location of aquifers, on the basis of which further calculations can be carried out.

Any of the soils is characterized by its load resistance, that is, in fact, by its bearing capacity. This parameter can be expressed in kilopascals (kPa), but for calculations in the metric system it is more convenient to use the kilogram-force per square centimeter (kgf / cm²).

It is clear that the distributed pressure created by the mass of the planned house (taking into account also external loads on it) and the mass of the slab itself should not go beyond the specified limits. However, such a calculation will still not be objective enough.

When calculating the required thickness of the slab, it is better to operate with the values ​​of the optimal specific pressure on a particular soil - these indicators are determined specifically for slab foundations. The calculated value of the load from the entire structure, including the weight of the slab, should be as close as possible to the optimal ones, with a possible deviation not exceeding 20÷25%.

What is it for? It is important not to go to two extremes. If the optimal load value is exceeded, it is likely that the slab will begin to sink into the ground over time. However, a significant decrease in ground pressure is no less dangerous - a structure that is too light for specific conditions becomes too “floating”, that is, it can warp even with the slightest seasonal ground fluctuations.

Pay attention to the following:

• The second table does not show all types of soils. The fact is that on soils with a high bearing capacity, the construction of a slab foundation itself simply does not make much sense - you can get by with much cheaper options.
• In addition, two rows are highlighted in the table. In both of these cases, it is recommended to conduct an in-depth analysis of the technical and economic feasibility of building a slab foundation.

- In the case of sandy loam, it is possible that the construction of a conventional strip foundation can be much more profitable.

- Hard clays are highlighted because the density of their structure is sometimes deceptive. If there is a possibility of waterlogging of these layers, for example, by closely located aquifers with seasonal fluctuations in their filling, then a sharp loss in the bearing capacity of the soil cannot be ruled out. The slab, together with the building, will gradually “sink”. It is worth considering the issue of greater, perhaps, the appropriateness of using

So, in order to calculate the required thickness of the slab, it will be necessary to determine what distributed load the building itself will exert on the base, then find the difference with the optimal pressure value, and cover the remaining “deficit” with the mass of the reinforced concrete slab. Knowing the specific density of reinforced concrete, it is easy to calculate the volume, and having the area of ​​​​the slab as the initial data, it is possible to determine its optimal thickness. At the same time, do not forget to take into account the fact that the slab should protrude beyond the perimeter of all walls outwards by at least the value of its calculated thickness or even more - this already depends on the specifics of the project.

Below the reader will be offered a calculator in which this calculation algorithm is implemented. Of course, this application cannot compete with professional programs in terms of accuracy of calculations, but it can provide a useful service for “estimating” in the field of hand-made construction.

The calculator assumes that the developer has in his hands the design outlines of the future building, that is, it will not be difficult for him to determine the initial data. You will need to know the material and area of ​​\u200b\u200bthe walls (minus window and door openings), the area and type of ceilings, the area of ​​\u200b\u200bthe roof and the angle of steepness of its slopes (to take into account the snow load). The calculation program has already included the average values ​​of the specific gravity of materials of building structures, taking into account approximate operational loads (mass of decoration, furniture, large household units, dynamic loads from people living in the house, etc.).

How to correctly calculate the area of ​​\u200b\u200bstructures?

Since area values ​​\u200b\u200bare often used in calculations, it is worth giving appropriate recommendations on this matter. They are set out in a special article on our portal dedicated to, which, by the way, also has convenient calculators.

It is best to prepare the data necessary for the calculation in advance, write it out on a separate plate, and then proceed to the calculations.

Price per square meter with material - from 4800 rubles.

The foundation is established during the construction of structures of any area. Ideal for water-saturated and weakly bearing soils(if a high plinth device is not required, and the slab itself is the floor).

1. Reinforcement along the entire bearing plane, reinforcement A3 Ø 12-16mm (GOST 5781-82).
2. Sand cushion - 30cm.
3. Plate - 25cm.
4. Concrete M-300 V22.5 P4 F200 W6
5. The term for the manufacture of the foundation is 5-7 days.

Foundation based on a monolithic slab- this is a solid monolithic reinforced concrete slab, laid under the entire area of ​​​​the future house. The main distinguishing feature of this type of foundation from all others is the largest supporting area, which allows for high stability of the future structure. That is why it is chosen for heavy houses, as well as for construction on soils with low bearing capacity.

This foundation, precisely due to the large area, is able to better withstand the forces of heaving of the soil, under their action the entire slab rises and falls, and not its individual pieces and elements. As a result, a house or other object built on such a foundation is reliably insured against distortions.

Some technical features of a slab monolithic foundation.

A monolithic foundation slab is laid on a previously prepared base - a compacted pillow of sand and gravel. The thickness of the sand cushion is from 20 cm or more. After the base cushion is prepared, it is necessary to proceed with waterproofing.

The next stage is the manufacture of the reinforcing cage of the foundation, which should consist of two grids (upper and lower). It is important to consider that the frame grids must be interconnected. For the manufacture of a reinforcing cage of a monolithic foundation, reinforcement with a cross section (in other words, ribbed) with a diameter of 12-16 mm can be used.

It is important to understand that the requirements for reinforcement for a monolithic foundation are significantly different and an order of magnitude higher than for a strip foundation. If the tape experiences a bending load only along, then in a monolithic, similar loads appear both in the longitudinal and in the transverse direction. This is easy to explain: the width of the strip foundation is less than its height.

Moreover, torsional loads can also occur in a monolithic foundation. Therefore, the reinforcing frame in this type of foundation must be completely made of ribbed reinforcement, which provides better adhesion to concrete, as a result - higher strength indicators.

Reinforcement bars must be installed at a distance of 20-40 cm from each other. If we take the average and lay reinforcement in the foundation in increments of 30 cm, then it is easy to calculate that it will take 1 sq. M: 3 times 1 meter of reinforcement along, the same number across for each stiffening belt (and, as we remember, - two), here it is also worth adding 2 meters of reinforcement to connect the stiffening belts to each other - as a result, 14 meters of reinforcement.

As you can see, the consumption of reinforcement for the manufacture of a monolithic foundation is much higher. Than for other types of foundation arrangement. Similarly, we can say about the consumption of concrete, which allows us to conclude that the cost of building a foundation-slab is an order of magnitude higher than any other type of foundation.

A monolithic foundation can be smooth or with stiffeners, which are most often done on the underside of the slab. This makes it possible to make the slab as a whole more resistant to various kinds of loads and deformations, and also creates a significant barrier to its horizontal displacement. The upper side of the monolithic foundation slab remains smooth and may well serve as the floor for the basement or basement of the future house. In the case of building a house without a basement or basement, the use of a monolithic slab foundation is considered inappropriate, irrational.

Depending on the type of soil on the construction site and its characteristics, a monolithic foundation can be shallow or deep buried. To equip a deepened monolithic foundation, it is necessary to dig a foundation pit, which by itself implies the implementation of a much larger amount of work. The advantage of such a solution is the fact that, as a result, such a foundation is able to provide maximum bearing capacity and is able to withstand even the heaviest buildings.

In individual construction, the use of a buried monolithic slab foundation is a rarity, since there is no need for such high bearing capacity, there is no need to extract a large amount of soil (dig a ditch). If it is necessary to increase the strength indicators of a monolithic foundation, then a shallowly deepened monolithic foundation-slab is chosen.

For its arrangement, it is enough just to remove the fertile layer of soil and lay a pillow of sand and gravel. As a result, the upper surface of the foundation slab is slightly, but still above ground level. To ensure that such a foundation is resistant to heaving of the earth as a result of its freezing in winter, the soil around the foundation is insulated.

As you can see, the construction of a monolithic slab foundation requires a lot of building materials, but in the end it allows you to provide a large supporting area and high strength indicators.

In order to understand whether there is a need for such a large supporting area for construction, it is necessary at the design stage of the house to calculate the load of the house on the foundation and correlate these indicators with the bearing capacity of the soil in this area where construction is underway or planned.

It is advisable to choose a slab monolithic foundation in the case of a high level of groundwater, on weak soils. If the characteristics of the soil make it possible to get by with a smaller area of ​​​​support, it is worth giving preference to the tape type of foundation, which will significantly reduce the cost of laying the foundation for building a house.

The slab base is designed for buildings of various types. Such a foundation requires a considerable investment of materials, but the finished structure is reliable and as strong as possible.

Base-slab - for what objects is it used?

• earthworks on difficult soils;
• construction of structures in which the foundation plays the role of a floor base (in this case, it is mandatory to organize high-quality hydro and thermal insulation under it);
• construction of private houses without a basement high tier or underground.

It is advisable to equip the described type of foundation for buildings with a height of no more than 2-3 floors. Very often, such a foundation is erected in regions with a cold climate, in places where the ground freezes quite strongly during winter. For this reason, slab foundations are so popular in the Scandinavian countries and in the Far North.

Slab structures are classified as reinforced concrete monolithic structures, laid under the entire area of ​​the building or house under construction. This reduces the load on the soil, which in turn guarantees an increase in the resistance of the building to seasonal changes characteristic of different types of soil. In fact, the poured slab functions as one - a reliable and heavy-duty platform, which is not afraid of any local deformations.

In the conditions of heaving soils, the slab structure rises when the soil freezes (moreover, this process takes place evenly), and when a thaw occurs, it falls. Due to this feature of the work, slab bases are often called floating. There is one nuance here. Floating platforms are understood as non-buried platforms. They are installed strictly on the surface of the soil. It is clear that with such an arrangement, it will not work to equip the basement in the building.

If the slab deepens into the ground - below the mark where freezing of the soil is noted, we are already talking about a deepened base. The choice of a particular type of foundation depends on a number of factors. When designing a slab platform, the following is usually taken into account:

• freezing depth and general characteristics of the soil;
• permissible load on the platform (taking into account the characteristics of the terrain and the type of building being built);
• the need for additional strengthening of the foundation and the creation of drainage.

We add that in many cases the plate is reinforced with special stiffeners. They are mounted below or above the base. Important! Below the slab, the ribs are placed in cases where it is planned to build a basement tier in the house, above - if it is required to ensure the most rigid fixation of the structure with a sand cushion.

The device of slab bases - what you need to know?

The foundations we are interested in are built from materials with certain characteristics. Particular importance is attached to the properties of the concrete used. It should have the following stats:

• frost resistance - not less than F200;
• strength index - M-300 and above;
• mobility category - P-3;
• water resistance index - not less than W8.

A monolithic slab as a foundation is characterized by certain parameters. The most important of them is the thickness of the concrete platform. This indicator depends on the type of building. For example, for the construction of most private housing constructions made of brick and stone, the recommended slab thickness is 20–25 cm. But car garages, frame-panel houses and other light buildings can be safely placed on bases of 10–15 cm.

The device of a slab structure assumes the obligatory presence of a sand-gravel cushion under it. Its height, as a rule, is 0.2–0.4 m. Without such a pillow, the plates are not installed. The next condition for the arrangement of a monolithic platform is high-quality waterproofing. It is carried out on the sides of the structure, in its upper and lower parts. That is, we are talking about the comprehensive protection of the foundation from moisture. From below, it is isolated (in most cases) with bitumen-polymer, roll materials, which should be used at the stage of formwork construction.

The specified waterproofing products are mounted on a sand cushion with an overlap. The joints between the pieces of insulation are sealed using surfacing technology. To implement it, you need to use a special gas burner. Part of the protective material is left in reserve. With its help, the ends of the slab are protected (unused pieces are wrapped around the sides of the platform to be poured). The upper part of the foundation can be isolated in different ways. For these purposes, sprayed, coated or conventional roll compositions and products are used.

Slab layers

Foundation insulation is performed to reduce heat loss. It is most reasonable to perform this operation after pouring the base - under the screed (at the stage of arranging the floors). The so-called under-foundation thermal insulation is also allowed. It involves laying a monolithic platform directly on a layer of insulating products. Under-foundation insulation is rational for buildings that are not used constantly, but seasonally (dachas, country cottages for summer living). In other cases, thermal protection should be carried out under the screed.

Formwork for slabs is made according to the standard scheme, using wooden boards 2.5–3 cm thick. The elements of the structure must be assembled into shields, installed along the perimeter of the foundation to be poured, and then secured with pegs and struts as efficiently as possible. Such work is done without problems by hand and requires minimal building skills from home craftsmen.

When pouring the slab, it is allowed to use any fittings according to the class. Here you only need to take into account the method by which the metal bars will be attached to the frame. Private developers usually produce wire knitting. For this method, the reinforcement class is unimportant. Use any item. But when erecting frames using electric welding, it is advisable to use fittings marked A500C. It's designed specifically for welding. This process, we note, is carried out by means of electrodes with a cross section of at least 1.2 cm.

Advantages and disadvantages of monolithic platforms - let's understand

Let's look at the pros and cons of the designs we are interested in. Their main advantage is the possibility of do-it-yourself installation on any type of soil (including the most problematic ones). If the slab base is made correctly, focusing on the advice of specialists, it will not sag and deform during the entire service life. The bottom line is that the spatial reinforcement and the large area of ​​​​such a foundation minimizes its pressure on the soil (up to 0.1 kg per square centimeter), and also guarantees effective load transfer with so-called variable signs. The latter are formed as a result of earth movements and cause significant damage to the reliability of other types of foundations.

Other advantages of monolithic platforms:

• the optimal ratio of the relatively small thickness of the plate and its bearing potential.
• the possibility of self-filling;
• acceptable cost of arrangement and the speed of the required work (provided that the concrete is unloaded from the truck mixers directly to the site where the foundation is being built);
• the possibility of using the plate as a floor covering for basements, subfloors.

The disadvantages of the described foundation are not critical. The main disadvantage of the plates is the need for labor-intensive and cost-increasing moisture protection measures. In addition, you have to very carefully choose the site for laying the slab structure. It cannot be mounted on winding and uneven areas. In some cases, manually leveling the site to the required level of quality can be difficult. It is necessary to order special equipment for excavation work. But, if the platform for the foundation is initially quite flat, the cost of these activities is reduced to a minimum.

In general, the arrangement of a monolithic base is not cheap. But the simplicity of the work and the high reliability of the resulting foundation fully compensate for all costs.

Do-it-yourself foundation - technology, work procedure and important tips

The arrangement of the base slab should begin with calculations. It is impossible to perform this operation without the help of specialists. Many home craftsmen are not serious about this stage of work. They consult with neighbors and acquaintances who previously built a slab platform, perform calculations "by eye". Such an approach is to some extent justified in the construction of a small outbuilding, a barn, a garage, a small summer cottage. If you are building a house for permanent residence, do not spare the money and entrust all the necessary calculations to professional designers.

Monolithic slab before pouring concrete

Having decided on the dimensions and other characteristics of the foundation, we can begin to prepare the site for its arrangement. We remove the top layer of soil to the required depth (it is determined in the calculation). Carefully level the site. No holes or bulges should remain on its surface. At the bottom of the pit made, we pour sand and crushed stone (or gravel). After compacting these materials, the height of the cake should measure:

• 30–40 cm for heaving and clay soils;
• 15–20 cm for sandy and normal soils.

Advice. On wet and swampy soils, we make a cake strictly with sand and gravel. The latter performs the function of additional protection of concrete from water. On other soils, gravel can be safely used instead of crushed stone.

Then we lay the introductory parts of the sewer system, water supply and other networks, after which we construct concrete preparation. It is understood as a screed with a thickness of about 10 cm. It is poured directly onto a pillow of sand and gravel. It is most convenient to make a screed from ready-made dry mixes. They are sold in all building stores. We recommend purchasing compositions based on sand concrete.

After it hardens, we lay roofing material (another type of waterproofing agent) on the concrete preparation. We solder the seams between the individual parts of the protective material. From above we cover a layer of thermal insulation with a heater. You can use expanded polystyrene extruded materials or foam. If the building will not be used in the cold season, the insulation can not be installed.

Now, on a cake made of sand, hydro- and heat-shielding materials, we install a reinforcing mesh cage. We make it from bars of 1.2–1.6 cm. The recommended parameters of the frame cells are from 20x20 to 30x30 cm. The next stage is the assembly of formwork from boards (we indicated their required thickness above). Separate structural elements are fastened with self-tapping screws. They need to be installed at the corners of the resulting shields. If desired, fiber boards can be used instead of boards. With their help, fixed formwork is built. Its parts are fixed with metal ties and corners, as well as props. It is not required to dismantle such a structure after pouring concrete. But the costs of fiberglass structures are significantly higher than those of wood.

Pouring concrete mix. The process is done in one go! It is necessary to pour the entire solution at once, without stretching the operation for hours and days.

Concrete must be rammed and leveled using special vibrators (they are called deep), or manually. Then we smooth the resulting base, cover it with plastic wrap, leave it for 20-30 days. Note. Concrete must be watered every day.

When the solution gains a sufficient level of density, polymer waterproofing should be applied to the ends of the slab, and then the made base should be insulated with polystyrene plates. That's the whole scheme for arranging a slab base. Fill it with all the above recommendations and your house will stand on a solid foundation for decades!