How to make a slab foundation

  How to make a slab foundation

Formwork scheme for a monolithic slab

10. After installing the reinforcement layer, the platform is filled with concrete. It must have a sufficient degree of mobility, so that the rubble does not get stuck between the reinforcement bars.

11. The solution is prepared according to the recommendations of a specific cement manufacturer. 10 kg of cement is usually taken 30 kg of clean sand without admixture of clay and 50 kg of gravel.

12. The flooded solution is carefully leveled and left to dry.

The proportions of the preparation of the solution for the foundation of cement M400

Watch the video: the foundation of a monolithic slab do it yourself
Part 1

Part 2

The foundation “plate” with your own hands – step by step instructions

The slab foundation is sometimes called floating because it is located almost on the surface, the depth of such a base is insignificant, not more than 1 m. The slab foundation, due to the width around the perimeter, does not warp, and does not heel, it preserves the geometry of the building for many years. The monolithic plate can repeat the movements of unstable soil, rise during the soil freezing and descend with a thaw, therefore there are no fractures and cracks in buildings built on this basis.

In this article I will consider step-by-step instructions for creating a foundation like “slab”.

Features of the slab base

The undoubted advantages of the slab foundation are:

  • Resistance to heavy loads.
  • Reliability and durability.
  • The integrity of the structure.
  • No shrinkage.

Monolithic slab foundation laid for the budget, but sometimes it is the only way to build a building on the site:

  • Weak and problematic soil.
  • Great weight of the building.
  • Bulk grounds.
  • Strong heaving and uneven compression of the soil.
  • High groundwater level.

The schematic diagram of the device slab foundation involves: sand pad, waterproofing and reinforced concrete slab.

The thickness of the monolithic slab basement is determined by the weight of the future construction:

  • 100 mm – for light buildings: garages, frame buildings, or buildings of light blocks. In the outbuildings, the upper part of the slab serves as a floor.
  • Up to 250 mm – for large full brick, concrete slab, stone, houses up to 3 floors, with heavy ceilings.


Waterproofing slab foundation should be given special attention. At the bottom of the foundation waterproofing is arranged during the construction phase of the formwork. It is preferable to use bitumen-polymer materials that are laid on the pillow, overlapped and then the joints are sealed by fusing using a gas torch. From the sides, a reserve of waterproofing material is left, which is then wrapped on a slab. The top is isolated from moisture by roll, coating or sprayed compounds.

In most cases, slab foundation is insulated under the base. For residential buildings it is recommended to put insulation on the finished slab under the floor screed. It is mandatory to insulate the ends of the foundation and the perimeter across the entire width of the blind area, laying the insulation under the main material of the blind area.

It is possible to warm with any material, but the most effective today is extruded polystyrene and foam, the optimal layer is 50-100 mm.

Private developers for the organization of the plate can use road concrete slabs, which are held together with a solution. But this method requires the use of technology and additional leveling of the surface, so it is not entirely profitable for the budget.

Monolithic slab foundation

The device of a shallow-depth monolithic slab assumes that it will serve as an overlap of the basement, designed for a low basement and no basement.

  • the minimum depth of the pit is to remove the vegetative layer of soil;
  • maximum – optimal depth – 500-700 mm;
  • It is recommended to remove the soil to a relatively dense soil.

Sand pillow

The height of the sand cushion depends on the stability and heaving of the soil. The usual recommended layer is 15-30 cm., Which must be carefully tamped so that no traces of the sole remain on the surface. In order not to damage the pillow, sometimes it is poured with a 10 cm layer of cement screed, a solution of m-100 will do.

Then, on a sandy pillow, a layer of rubble is arranged in 10-15 cm.

In cold regions, insulation is placed on the rubble in 1-2 layers.

Do not forget to bring all engineering communications under the slab foundation.

Insulation covered with a waterproofing layer, which should be carefully sealed.

After all the preliminary work, formwork is arranged, the boards for it should not be thinner than 25 mm. The formwork is fastened with pegs and struts, so that the liquid concrete does not crush the mold.


Based on the nature of the soil, you should make a reinforcement cage. For light buildings, and, consequently, low slabs, fit the grid of reinforcement with a diameter of 8 mm. For more massive structures, it is recommended to build a two-layer frame of ribbed reinforcement 10-16 mm, with a cage of 200 * 200 mm, the size of the cage up to 500 mm is allowed. The cage cells must be the same throughout the entire slab area.

IMPORTANT. The reinforcement structure in the slab foundation must be covered with a layer of concrete 50 mm each from all sides.

Concreting is carried out simultaneously, all at once the plate, it is necessary to achieve strength and solidity of the structure, without the formation of temperature joints.

The slab foundation with stiffeners is a monolithic slab with a height of 200-250 mm, with additional ribs deepened down to give the base tenacity with the ground. The ribs are arranged around the perimeter of the foundation, sometimes also in the middle for the immobility of the slab during the swelling of the soil.

Slab foundation – the most durable type of foundation, which has found wide application in private construction. The cost of such a design is more than compensated for by the ease and simplicity of the foundation, as well as by the reliability and safety of the buildings built on it.

A small video demonstrating the appearance of the slab foundation visually:

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How to make a base plate on the site?

  • Slab foundation. varieties and benefits
    • How does the base plate work?
    • Slab foundation technology
  • How to perform waterproofing base plate?
    • Methods of waterproofing slab foundation
    • How is the waterproofing base plate: technology

One of the most common types of base is a base plate. In most cases, this type of foundation is used on inhomogeneous and floating soils. The foundation is a monolithic structure that is not afraid of any changes in the ground.

The foundation of the slab type is laid completely under the entire area of ​​the building, and not just under the walls.

A slab of this type will move along with a private house, thereby protecting it from destructive actions. Experts consider the foundation of this type the most reliable and sustainable.

Slab foundation: variations and benefits

There are the following types of base monolithic slabs:

Diagram of the slab foundation device.

  • with grillage;
  • without grillage;
  • basement plate;
  • the warmed Swedish plate;
  • with stiffeners.

The base plate has the following advantages:

  1. Versatility. Suitable for the house, which is made of any materials (brick, aerated concrete, wood, etc.).
  2. The possibility of building on almost any soil.
  3. Reliability. With proper operation of the monolithic foundation is the most reliable.
  4. You can not do geological testing.
  5. Does not undergo heaving of soils (when performing the blind area and warming the slab).

You should know in what cases it is recommended to fill the slab foundation.

It is not always advisable to use a strip foundation. Most often this is due to the available properties of the soil on which it is planned to produce construction.

It is optimal to lay a slab foundation with your own hands when the ground:

  • subject to interseasonal excessive swelling;
  • has high humidity;
  • groundwater was found in the upper layers of the soil.

Diagram of the slab foundation device with stiffeners.

This type of foundation not only proved itself well in such conditions, but in some cases it may be the only opportunity to perform the construction of buildings that are large in size.

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How does the base plate work?

The main difference between the foundation slab and the pile or strip foundation lies in its placement. It will be necessary to lay it not under the walls of the building, but under the entire area of ​​a private house. The building must be installed on a reinforced concrete pillow. That is why all ground movements will not harm the foundation or a private house.

The mass of the structure and slab is so high that it can withstand almost any temporary ground movement. If the pressure exceeds the calculated norms, the house will rise along with the stove, and there will be no negative consequences.

Laying the foundation slab is much easier than erecting a strip foundation or installing screw piles. It is worth noting that the price of this type of foundation is not the lowest. The structure consists of solid concrete, which is reinforced with reinforcement. The entire foundation is installed in the place that you need to pre-mark on the site.

If you don’t want to cast a solid slab, while the ground is relatively dry and rather dense, you can use FL foundation slabs that need to be laid in a pit. Their installation will provide a solid foundation.

Marking the pit under the slab foundation.

Before laying the foundation will need to perform some calculations. This is done during the preparation of the project, but you can do this action by using special computer programs.

It makes no sense to give an example of the calculation of the base plate. therefore, the values ​​that are regulated by SNiP 2.03.0184 “Structures made of reinforced concrete” and DBN B.2.1-10-2009 “Foundations and foundations of structures” should be taken into account. It is worth noting that in most cases for a light one-story private house you will need to pour a concrete base with a thickness of more than 30 cm, which should be necessarily reinforced with a grid with cells of 20×20 cm. This grid is laid out from metal rods with a section of 12-16 mm.

Before installing the reinforcement, you will need to properly perform waterproofing, which is able to protect the concrete from the negative effects of moisture during temperature changes in the winter time period.

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Slab foundation technology

The formation of a sand pillow.

First of all, topsoil is removed with a thickness of more than 40-50 cm. The layer will depend on the size of the building. The boundaries of the pit on each side must necessarily be 1 m larger than the future foundation. This will need to be done for the installation of formwork panels that prevent the poured concrete from cracking.

When the foundation pit has been prepared and all communication pipes have been laid, it will be possible to proceed to backfilling the compensation pad. The height of this cushion is in the range from 25 to 30 cm. Everything will depend on the type of soil. The pillow should be carefully tamped.

If the soil is marshy or has a high humidity, to improve the waterproofing properties in the sand bedding you will need to add crushed stone.

Next will be the opportunity to proceed with the installation of formwork. Such a process will not differ from activities when working with concrete. It will be necessary to install restrictive shields around the perimeter of the foundation being manufactured.

In most cases, shields can be made from waterproof plywood or wood. They will need to be securely fastened in their places so as to prevent their displacement in the process of pouring concrete.

For the formwork of a thick base plate, construction boards that are firmly fixed in the soil are best suited. Wooden timber must be laid so that in the future it served as a measure of the height at which fresh concrete could be poured evenly.

Further, the dimensions of the working volume of the pit are measured.

The scheme of the device formwork.

As soon as the formwork is ready, you will need to expand the film for waterproofing. The bottom of the pit should not be covered. If a thick slab foundation is made, it is necessary to build panels 15 cm up the inside of the formwork. The film is fixed with nails. Next, a static calculation is performed and steel reinforcement is mounted. Soils with a high bearing capacity for communication with the foundation often only need constructive reinforcement. To do this, set the steel grate at the top of the plate. In this case, you need to pay attention to the correct lateral overlap. Most often 30 cm will suffice. If the grille bends, it must be leveled with a strapping wire.

On the lower struts will need to place the grating of steel. Further along the edge, a reinforcement cage is installed. It is quite difficult to bend the reinforcing bars with our own forces, therefore it is better to entrust the task to the reinforcement supplier.

The upper steel gratings are placed on the following struts. These designs should be made in various heights. With their help, it is necessary to fix the gap between the lower and upper layers of the steel grating. To ensure a stable position of the steel gratings, you will need to install spacers in the form of continuous tracks. The distance between such tracks should be equal to 1 m. At the end, the upper reinforcement is firmly tied with wire from the bottom. It is important to note that after the concrete work the metal should not be visible on the entire surface.

Concrete mortar preparation scheme.

Before pouring concrete, you need to think about grounding the base. To do this, you need to make a closed ring of galvanized steel tape. This ring is embedded in steel reinforcement or the base of the outer side of the foundation. Connecting tires should be bent high at the corners, where metal pipes and lightning conductor connections are provided.

Concrete must be used exclusively brand M300 or higher. It is recommended to fill the entire volume in 1 day, so no need to resort to self-mixing. Concrete must be ordered in a mixer of the appropriate volume. This will significantly reduce the time to carry out all the necessary work and save their own strength. The concrete purchased from the factory is guaranteed to be manufactured in compliance with all existing technological standards.

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How to perform waterproofing base plate?

Excessive moisture is the main enemy of the builder. Because the high-quality waterproofing of a base plate is not arranged. quite often you have to remodel private houses and carry out repairs in them. Inexperienced builders often encounter similar problems, but they can easily be avoided if one studies this issue in detail in advance.

You should know what the absence of a reliable hydro-barrier leads to. Water is aggressive to most building materials. Concrete from which the foundation is made is no exception. Concrete has a porous structure that can easily absorb water. The penetrating moisture of the soil contains admixtures of mineral salts: chlorides, sulphates and hydrocarbonates. They crystallize in the pores of the concrete, greatly increasing in volume. As a result, the array will collapse.

The scheme of reinforcement slab foundation.

The reverse situation may occur. Water enters the pores of the concrete, begins to wash salt out of it, as a result of which the destruction of this building material will occur. Also, as a result of poor-quality waterproofing, the wall material will “pull” moisture from it. As a result, there may be dampness in the room, mold on the walls, damage to the finishing materials and the need for a new repair.

In any building premises that have a basement, it is imperative to perform waterproofing of the foundation slab. It must be performed even in the absence of groundwater in the basement area of ​​the premises.

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Methods of waterproofing slab foundation

This problem can be solved in several ways. Each of them has its advantages and disadvantages. The most common types today are the following:

  1. Coating This waterproofing is durable, gives a good result, quite simple to use.
  2. Penetrating. More modern way to cut off moisture. The difference of the method lies in the fact that when applying waterproofing of this type there will be a reaction of the composition with concrete, therefore during subsequent contact with moisture the construction material crystallizes and seals all its pores.
  3. Roll. A method that has been used for a long time. The durability of this waterproofing is not too big.

The scheme of waterproofing slab foundation.

The main problem in the foundation slab device is the waterproofing of the structure at the bottom, because it has a large area. In most cases, such work can be done in 2 ways. There is an opportunity to use obmazochny and rolled materials.

It should be noted that it is not recommended to use roofing material for waterproofing. This roll material used to be quite often used in construction. For this, bitumen was applied on a cardboard base. Its durability is not too large, because the paper base quickly comes into disrepair, the material has a low bending strength, is not the best resistance to the effects of low and high temperatures, ultraviolet radiation, etc. Bitumen, which is used in the production of roofing material, does not have good elasticity and viscosity. As a result, the material will quickly crack, and the waterproofing barrier will lose its tightness.

Modern materials for the device roll waterproofing are rubemast, glass insulation, etc. They are made on the basis of fiberglass and fiberglass. This gives them high strength. The composition of bitumen, which is impregnated with the base, includes various modifying additives. That is why the material has become elastic, has good bending strength, resistance to low and high temperatures.

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How is the waterproofing base plate: technology

Rolled waterproofing under the slab foundation is convenient to use, because it is simply laid on a pillow of sand and gravel, without the need to perform an additional screed. Between strips of material, the joints will need to be carefully glued with bitumen mastic. Laying is carried out simply and quickly, from the devices you need to purchase only a burner to heat the mastic. Along the perimeter of the base, the strip of material for waterproofing is bent upward by about 12-15 cm.

Scheme of double-sided waterproofing.

Obmazochnoy waterproofing using bitumen mastic is a modern way to drain water from the base plate. For it you will need to apply the modified bitumen on the base of concrete with a roller, brush, spray. The difficulty lies in the fact that to perform the waterproofing of the base sole, it is necessary to lay a layer of cement screed on a cushion of sand and rubble, on which a layer of bitumen mastic is subsequently applied. Over the slab, waterproofing is applied to the top and sides of the foundation.

In the same way, penetrating waterproofing of the foundation slab is performed. On the basis of sand and gravel is laid cement screed, which will need to cover the roll waterproofing material. After pouring the slab, it is necessary to apply penetrating insulation on the top and side surfaces. The principle of its operation is the following: chemical reaction between lime (calcium hydroxide), which is contained in concrete, capillary moisture, which is in the thickness of concrete, as well as active substances, which are part of the material for waterproofing.

Diagram of the construction of the slab basement in stages.

As a result, the pores of the concrete are sealed with crystalline compounds that will prevent the penetration of water. In this case, this reaction will continue for a long time, continuing to seal small cracks in the thickness of the building material. This method of waterproofing the foundation slab is the most efficient, modern and high-tech.

You should also know how to waterproof the joints of the foundation slab. If the slab foundation is built from separate reinforced concrete structures, it will be necessary to pay attention to the waterproofing of the joints between all the existing components. Seams when laying are filled with concrete, which is able to absorb moisture. To prevent this, the joints will need to be sealed with special polyurethane cords, coating waterproofing and sealants.

The slab foundation is not only a universal solution for almost any possible conditions, but also a reasonably reliable basis for a private house being manufactured.

In some cases, the calculated mass of a private house being manufactured exceeds the carrying capacity of the foundation, which leads to cracking of such a slab. If there is no possibility to use a different type of base, a ribbed slab foundation may be the best way out.

It differs from ordinary slab reinforcing ribs, which are directed from the base into the ground. The ribs will need to be further reinforced with metal rods with a cross section of 14-16 mm. Such a design will significantly increase the strength and bearing characteristics of the base.

Ivan, in this case, you need to build on a 10-liter bucket. Fill a full bucket with sand and add 1/3 of cement, mix everything 10 liters. or.

October 16, 2015

How is the calculation of finished concrete per 1 sq. M screed 5cm thick? How much sand and cement is required for this? So as not to buy too much. Want.

October 12, 2015

In different grades of concrete, if measured by volume, only the ratio of sand and rubble to cement changes, and water is always taken exactly half of the volume of cement.

October 20, 2015

Ivan, in this case, you need to build on a 10-liter bucket. Fill a full bucket with sand and add 1/3 of cement, mix everything 10 liters. or.

October 16, 2015

How is the calculation of finished concrete per 1 sq. M screed 5cm thick? How much sand and cement is required for this? So as not to buy too much. Want.

October 12, 2015

In different grades of concrete, if measured by volume, only the ratio of sand and rubble to cement changes, and water is always taken exactly half of the volume of cement.

A few additions: 1. If you need to perform high-quality waterproofing liquid rubber, it is desirable to apply geotextiles over the entire surface. Consumption.

September 23, 2015

How and what to make the top border of the foundation lining (natural stone. Plitnyak)?

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