Monolith how to do it right. Do-it-yourself foundation slab step-by-step instructions: how a monolithic foundation slab is constructed and stages of construction. Marking and excavation work

In houses made of brick, concrete or concrete blocks, the floors are usually made of reinforced concrete. They provide exceptional strength and earthquake resistance to the structure, and are also very durable and do not burn, which is important. There are several ways to construct reinforced concrete floors. The most common and universal is laying factory-made floor slabs. Such slabs are ordered from concrete factories and then installed using a crane and a team of workers. In cases where using a crane on a construction site is difficult, or when the house has a non-standard layout and it is difficult to lay out finished slabs, a monolithic floor slab is installed. In fact, you can fill a monolithic slab not only when there is evidence for it, but also simply because you consider it more appropriate. In this article we will tell you how to lay floor slabs and how to pour a monolithic slab. Not all work can be done independently, but it is still worth familiarizing yourself with the technology, if only to control the process on the construction site.

DIY monolithic floor slab

Monolithic flooring has a number of advantages compared to flooring made from ready-made reinforced concrete slabs. Firstly, the structure is strong and monolithic without a single seam, which ensures an even load on the walls and foundation. Secondly, monolithic filling allows you to make the layout of the house more free, since it can rest on columns. Also, the layout can involve any number of corners and crannies for which it would be difficult to select floor slabs of standard sizes. Thirdly, it is possible to safely equip a balcony without an additional support plate, since the structure is monolithic.

You can install a monolithic floor slab yourself; you don’t need a crane or a large team of workers. The main thing is to follow the technology and not skimp on materials.

Like everything related to construction, monolithic flooring begins with a project. It is advisable to order the calculation of a monolithic floor slab from a design office and not save on it. It usually involves calculating the cross-section of the slab for the bending moment at maximum load. As a result, you will receive the optimal dimensions for the floor slab specifically in your home, instructions on what reinforcement to use and what class of concrete. If you want to try to perform the calculations yourself, an example of calculating a monolithic floor slab can be found on the Internet. We will not focus on this. Let's consider the option of building an ordinary country house with a span of no more than 7 m, so we will make a monolithic floor slab of the most popular recommended size: from 180 to 200 mm thick.

Materials for the manufacture of monolithic floor slabs:

• Formwork.
• Supports for supporting the formwork at the rate of 1 support per 1 m2.
• Steel reinforcement with a diameter of 10 mm or 12 mm.
• Concrete grade M 350 or separately cement, sand and crushed stone.
• Bending device for reinforcement.
• Plastic supports for fittings (clamps).

Technology for pouring a monolithic floor slab includes the following steps:

1. Calculation of the floor slab if the span is more than 7 m, or the project involves supporting the slab on a column/columns.
2. Installation of deck type formwork.
3. Reinforcement of the slab with steel rods.
4. Pouring concrete.
5. Compacting concrete.

So, after the walls have been driven to the required height, and their level is almost perfectly leveled, you can begin to install a monolithic floor slab.

The construction of a monolithic floor slab assumes that concrete will be poured into horizontal formwork. Sometimes horizontal formwork is also called “deck”. There are several options for its arrangement. First - rental of ready-made removable formwork made of metal or plastic. Second - making formwork on site using wooden boards or sheets of moisture-resistant plywood. Of course, the first option is simpler and preferable. Firstly, the formwork is collapsible. Secondly, it offers telescopic supports, which are needed to support the formwork at the same level.

If you prefer to make the formwork yourself, then keep in mind that the thickness of the plywood sheets should be 20 mm, and the thickness of the edged boards 25 - 35 mm. If you knock down panels from edged boards, then they need to be tightly adjusted to each other. If gaps are visible between the boards, then the surface of the formwork should be covered with waterproofing film.

Installation of formwork is carried out in this way:

• Vertical support posts are installed. These can be telescopic metal stands, the height of which can be adjusted. But you can also use wooden logs with a diameter of 8 - 15 cm. The step between the racks should be 1 m. The racks closest to the wall should be located at least 20 cm from the wall.
• Crossbars are placed on top of the racks (a longitudinal beam that will hold the formwork, an I-beam, a channel).
• Horizontal formwork is laid on the crossbars. If not ready-made formwork is used, but home-made one, then transverse beams are laid on top of the longitudinal beams, on which sheets of moisture-resistant plywood are placed on top. The dimensions of the horizontal formwork must be adjusted perfectly so that its edges rest against the wall without leaving gaps.
• The height of the pillar supports is adjusted so that the upper edge of the horizontal formwork coincides with the upper edge of the wall masonry.
• Vertical formwork elements are installed. Taking into account the fact that the dimensions of a monolithic floor slab must be such that its edges extend 150 mm onto the walls, it is necessary to construct a vertical fence exactly at this distance from the inner edge of the wall.
• The last time the horizontal and even position of the formwork is checked using a level.

Sometimes, for the convenience of further work, the surface of the formwork is covered with a waterproofing film or, if it is made of metal, lubricated with machine oil. In this case, the formwork can be easily removed, and the surface of the concrete slab will be perfectly flat. The use of telescopic racks for formwork is preferable to wooden supports, since they are reliable, each of them can withstand a weight of up to 2 tons, and microcracks do not form on their surface, as can happen with a wooden log or timber. Renting such racks will cost approximately 2.5 - 3 USD. per 1 m2 of area.

After arranging the formwork, a reinforcement frame made of two meshes is installed in it. For the manufacture of the reinforcement frame, steel reinforcement A-500C with a diameter of 10 - 12 mm is used. These rods are used to knit a mesh with a mesh size of 200 mm. To connect longitudinal and transverse rods, 1.2 - 1.5 mm knitting wire is used. Most often, the length of one reinforcing rod is not enough to cover the entire span, so the rods will have to be connected to each other lengthwise. To make the structure strong, the rods must be connected with an overlap of 40 cm.

The reinforcing mesh should extend onto the walls by at least 150 mm if the walls are made of brick, and by 250 mm if the walls are made of aerated concrete. The ends of the rods should not reach the vertical formwork along the perimeter by 25 mm.

Reinforcement of a monolithic floor slab is carried out using two reinforcing meshes. One of them - the bottom one - should be located at a height of 20 - 25 mm from the bottom edge of the slab. The second - the top - should be located 20 - 25 mm below the top edge of the slab.

In order for the lower mesh to be located at the required distance, special plastic clips. They are installed in increments of 1 - 1.2 m at the intersection of the rods.

The thickness of the monolithic floor slab is taken at the rate of 1:30, where 1 is the thickness of the slab, and 30 is the span length. For example, if the span is 6 m, then the slab thickness will be 200 mm. Considering that the grids should be located at a distance from the edges of the slab, the distance between the grids should be 120 - 125 mm (from a slab thickness of 200 mm we subtract two gaps of 20 mm and subtract 4 thicknesses of reinforcing rods).

To space the meshes at a certain distance from each other, they are made from 10 mm reinforcing rod using a special bending tool. special clamps - stands as in the photo. The upper and lower flanges of the clamp are 350 mm. The vertical size of the clamp is 120 mm. The installation step of the vertical clamps is 1 m, the rows should be staggered.

Next step - end clamp. It is installed in increments of 400 mm at the ends of the reinforcement cage. Serves to strengthen the support of the slab on the wall.

Another important element is connector of upper and lower mesh. You can see what it looks like in the photo. It is necessary so that the spaced grids perceive the load as one whole. The installation step of this connector is 400 mm, and in the area of ​​support on the wall, within 700 mm from it, in steps of 200 mm.

Pouring concrete

It is better to order concrete directly from the factory. This makes the task much easier. In addition, pouring the mortar from a mixer in an even layer will ensure exceptional strength of the slab. The same cannot be said about the slab, which was poured manually with breaks to prepare a new portion of the solution. So it is better to pour concrete immediately in a layer of 200 mm, without interruptions. Before pouring concrete into the formwork, it is necessary to install a frame or box for technological openings, for example, a chimney or ventilation duct. After pouring, it must be vibrated with a deep vibrator. Then leave to dry and gain strength for 28 days. During the first week, the surface must be moistened with water, only moistened, and not filled with water. After a month, the formwork can be removed. The monolithic floor slab is ready. For installation of floor slabs, the price includes the cost of reinforcement, concrete, rental of formwork and ordering a mixer machine, as well as a concrete pump. In fact, it comes out to about 50 - 55 USD. per m2 of flooring. You can see how the floor slab is poured with concrete in the video demonstrating the installation of floor slabs.

How to lay floor slabs correctly

The use of factory-made monolithic reinforced concrete floor slabs is considered more traditional. The most popular are PC slabs - slabs with round voids. The weight of such slabs starts from 1.5 tons, so laying floor slabs with your own hands is impossible. A crane is required. Despite the apparent simplicity of the task, there are a number of nuances and rules that must be followed when working with floor slabs.

Rules for laying floor slabs

The prefabricated floor slab is already reinforced at the factory and does not require additional reinforcement or formwork. They are simply laid in a span supported on the walls, following some rules:

• The span should not be more than 9 m. This is the length of the slabs that are the largest.
• Unloading and lifting of slabs is carried out using special equipment provided by the project. For this purpose, the slabs have mounting loops to which the mounting slings are hooked.
• Before laying floor slabs, the surface of the walls on which they will be laid must be leveled. Large height differences and distortions are not allowed.
• The slabs should rest on the walls by 90 - 150 mm.
• The slabs must not be laid dry; all cracks and technological seams must be sealed with mortar.
• The location of the slabs must be constantly monitored in relation to the walls and supporting surfaces.
• The slabs are laid only on load-bearing walls, all partitions are installed only after the installation of the floors.
• If you need to cut a hatch in the ceiling, then it must be cut at the junction of two slabs, and not in one slab.
• The plates should be located as close to each other as possible, but with a gap of 2 - 3 cm. This will ensure earthquake resistance.

If there are not enough floor slabs to cover the entire span, and there remains, for example, 500 mm, then there are different ways to lay floor slabs in this case. The first is to lay the slabs end to end, leaving gaps along the edges of the room, then seal the gaps with concrete or cinder blocks. The second is laying slabs with uniform gaps, which are then sealed with concrete mortar. To prevent the solution from falling down, formwork is installed under the gap (a board is tied up).

Floor slab laying technology

In the process of laying floor slabs, there must be clear coordination of actions between the crane operator and the team receiving the slab. To avoid injuries at the construction site, as well as to comply with the entire technological process and rules described in SNiPs, the construction foreman must have a technological map for installing floor slabs. It indicates the sequence of work, the quantity and location of equipment, special equipment and tools.

It is necessary to start laying floor slabs from the flight of stairs. After laying the slabs, their position is checked. The slabs are laid well if:

• The difference between the lower surfaces of the plates does not exceed 2 mm.
• The height difference between the upper surfaces of the slabs does not exceed 4 mm.
• The height difference within the site should not exceed 10 mm.

As the installation diagram for floor slabs demonstrates, after laying the slabs, they must be connected to each other and to the walls using metal connecting parts. Work on connecting embedded parts and connecting parts is carried out by welding.

Don't forget to follow safety precautions. It is not allowed to carry out work using a crane in an open area with a wind of 15 m/s, as well as during ice, thunderstorms and fog. When moving the slab using a crane, the installation team should be away from the path along which the slab will move, on the opposite side of the feed. Despite the fact that using the services of a professional foreman and a team of installers significantly increases the cost of installing floor slabs, this is still not the case when you can save money. The foreman must provide the project.

Before ordering slabs from the factory, it is necessary to carry out preparatory work. It is better to coordinate the delivery time of the machine with slabs and the crane at the same time, so as not to overpay for downtime of special equipment. In this case, the installation of the slabs can be carried out without unloading, directly from the vehicle.

Preparatory work before laying floor slabs

First - flat supporting surface. The horizon should be almost ideal; a height difference of 4 - 5 cm is unacceptable. First of all, we check the surface of the walls, then, if necessary, level it with concrete mortar. Subsequent work can be carried out only after the concrete has acquired maximum strength.

Second - ensure the strength of the support area. If the walls are built from brick, concrete or concrete blocks, then no additional measures need to be taken. If the walls are built from foam blocks or gas blocks, then before laying the slabs it is necessary to fill in the reinforced belt. Correct laying of floor slabs requires that the supporting surface must be strong enough to support the weight of the slab and not deform along the abutment line. Neither aerated concrete nor foam concrete have the necessary strength. Therefore, formwork is installed along the entire perimeter of the building, a reinforcement frame made of 8 - 12 mm rod is installed in it, and then everything is filled with concrete with a layer of 15 - 20 mm. Further work can be continued only after the concrete has dried.

Third - install mounting towers. Telescopic supports, as described in the section on installing a monolithic floor slab, are installed in increments of 1.5 m. They are designed to take on the weight of the slab if it suddenly slips out of its place. After installation, these towers are removed.

Installation of hollow core slabs using a crane

After the freshly poured concrete has acquired sufficient strength and has dried, the installation of the floor slabs can begin. For this, a crane is used, the lifting capacity of which depends on the size and weight of the slab; cranes of 3 - 7 tons are most often useful.

Stages of work:

• Concrete mortar is applied to the supporting surface in a layer of 2 - 3 cm. The depth of application of the mortar is equal to the depth of support of the slab, i.e. 150 mm. If the slab rests on two opposite walls, then the solution is applied only to two walls. If the slab rests on three walls, then on the surface of three walls. The actual laying of the slabs can begin when the mortar reaches 50% of its strength.

• While the solution dries, the crane operator can hook the slings to the slab fasteners.
• When the crane operator is given a signal that the slab can be moved, the team of workers must move away from the place where the slab is moving. When the slab is very close, the workers hook it with hooks and turn it around, thereby dampening the oscillatory movements.

• The stove is directed to the right place, one person should stand on one wall, and the other on the opposite. The slab is laid so that its edges rest on the wall at least 120 mm, preferably 150 mm. After installation, the slab will squeeze out excess mortar and evenly distribute the load.

• If there is a need to move the slab, you can use a crowbar. Its position can only be aligned along the laying area; the slab cannot be moved across the walls, otherwise the walls may collapse. The slings are then removed and a signal is given to the crane operator to pick them up.
• The procedure is repeated for all slabs without exception. The rules for installing floor slabs suggest that the alignment of the slabs should be done along the bottom edge, since it is the bottom surface that will be the ceiling in the room. Therefore, the slab is laid with the wider side down and the narrower side up.

You may come across a recommendation that reinforcement must be placed in the area where the slab is supported. Proponents of this method say that it is more convenient and easier to move the stove. In fact, placing anything other than concrete mortar under the slab is prohibited by the technical map. Otherwise, the slab can easily move out of the support area, as it will slide along the reinforcement. In addition, the load will be distributed unevenly.

Laying floor slabs on the foundation is practically no different from laying interfloor slabs. The technology is exactly the same. Only the surface of the foundation must be thoroughly waterproofed before laying the slabs. If the project provides for non-standard support of floor slabs, then special steel elements are used for this. Such work should not be carried out without a specialist.

Anchoring - tying the slabs together - can be done in two ways, depending on the project.

First - tying slabs with reinforcement. Reinforcing rods with a diameter of 12 mm are welded to the fastening embedded elements on the slab. For slabs from different manufacturers, the location of these elements may be different: in the longitudinal end of the slab or on its surface. The strongest connection is considered to be a diagonal connection, when the plates are connected to each other with an offset.

The slab must also be connected to the wall. Why is reinforcement built into the wall?

Second way - ring anchor. In fact, it looks like an armored belt. Formwork is installed around the perimeter of the slab, reinforcement is installed into it and concrete is poured. This method slightly increases the cost of laying floor slabs. But it's worth it - the slabs end up clamped on all sides.

After anchoring, you can begin to seal the cracks. The gaps between the floor slabs are called rustications. They are filled with concrete grade M150. If the gaps are large, then a board is tied from below, which serves as formwork. If the gaps are small, then the floor slab will be able to withstand the maximum load the very next day. Otherwise you need to wait a week.

All modern slabs with round voids are produced with the ends already filled. If you purchased slabs with open holes, then they need to be filled with something 25 - 30 cm deep. Otherwise the slab will freeze. You can fill the voids with mineral wool, concrete plugs, or simply fill them with concrete mortar. A similar procedure must be performed not only on those ends that face the street, but also on those that rest on the internal walls.

The price for laying floor slabs depends on the amount of work, the area of ​​the house and the cost of materials. For example, the cost of PC floor slabs alone is approximately 27 - 30 USD. per m2. The rest is related materials, crane rental and workers, as well as the cost of delivering the slabs. Professional teams have very different prices for installation of floor slabs, from 10 to 25 USD. per m2, maybe more depending on the region. As a result, the cost will be the same as for pouring a monolithic floor slab.

Laying floor slabs: video example

Among all types of foundations chosen by private developers for the construction of their country houses and outbuildings, the undisputed leader in frequency of use are foundations. However, quite often the specifics of the soil 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 base of the strip foundation, which makes it an unprofitable solution, especially if we are talking about the construction of a relatively small in size and total mass building. We have to look for other options that are more economically justified, but at the same time not inferior in terms of load-bearing capabilities.

One such solution could 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 low bearing capacity. And the comparative simplicity of constructing such a foundation makes it completely doable on one’s own. So, the topic of this publication is a do-it-yourself foundation slab, step-by-step instructions, from calculations to practical implementation.

Typical diagram of a monolithic slab foundation

A slab foundation does not require a deep location; rather, on the contrary, its load-bearing capacity and “floating” features will appear precisely when it is sufficiently close to the surface of the earth. In this case, even frost heaving 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.

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

1 – Compacted soil – the bottom of a pit dug for the foundation.

2 – A carefully compacted “cushion” of sand, sand-gravel mixture, or crushed stone, which promotes uniform distribution of loads, becomes a kind of damper that softens the effects of ground vibrations. Layer-by-layer filling and compaction of such a “pillow” is practiced, with one or another alternation of materials, or homogeneous, using ASG.

3 – A layer of geotextile (dornite), which will give the sand “cushion” a kind of “reinforcement”, will prevent it from silting or washing away 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. Thus, such a layer is often placed between the surface of the compacted bottom of the pit and the first layer of sand “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 avoiding interpenetration. In this case, the location of the gravel or crushed stone layer above the sand seems to be more optimal - because capillary “suction” of ground moisture from below is almost completely eliminated.

4 – A layer of so-called concrete preparation. This element of the overall slab foundation “pie” is often neglected for reasons of saving material and reducing the overall duration of work. Meanwhile, such concrete preparation plays a significant role - it allows you to achieve a “clear geometry” of the base for further pouring the foundation or laying insulation materials, and makes it possible to very efficiently install the hermetically sealed waterproofing required for the slab.

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

6 – The monolithic slab itself with the calculated thickness.

7 – reinforcing belt of a concrete slab. Its classic design consists of two levels of reinforcement grids connected to each other to give the structure volume with special clamps. The arrangement of the reinforcement is planned in such a way that a layer of concrete of about 50 mm is created between the rods and the edges of the slab at the top, bottom and ends - in order to prevent the start of metal corrosion processes.

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

The easiest to implement and probably the most common option is a solid slab, the uniform thickness of which is maintained over its entire area.

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

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

A similar scheme is often practiced in cases where the useful use of a semi-basement or ground floor is planned - the slab simultaneously becomes the floor of these rooms. And from the grillages they begin laying the plinth.

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

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

This also turns out to be a kind of “symbiosis” of slab and strip foundations. Stiffening ribs are planned under external walls and capital internal partitions. Well, if internal partitions are not provided, then the ribs should be located parallel to each other and the shorter side of the perimeter of the house, with a pitch not exceeding 3000 mm.

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

In addition, wide possibilities for insulating the foundation slab open up - the same height difference on the main surface and on the stiffeners is often accomplished by laying durable thermal insulation material, for example, extruded. By the way, this approach 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 (USP) - the basis for houses with minimal energy consumption

The trend of building 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 USP. The main nuances are discussed in detail in the corresponding publication on 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 absence of a rigid connection between adjacent slabs makes such a foundation unstable to possible ground vibrations. For this reason, such a scheme is not widely used, and is practically not used in private residential construction. The only exception may be small-sized outbuildings, the area of ​​which is limited by the size of one standard slab, but this, as you understand, is extremely rare.

Application of slab foundation. Its main advantages and disadvantages

The use of a slab foundation will be fully justified on construction sites characterized by soils with reduced bearing capacity. It is usually resorted to where simpler schemes, such as shallow strip laying or columnar laying, are simply impossible due to the peculiarities of “geology”: the tendency of soils to frost heaving, horizontal “movements”, close proximity of aquifers, etc.

In addition, such a foundation, with careful calculations and design, can become a very reliable basis for multi-story construction. Uniform distribution of loads over a large area of ​​the base gives very low 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.

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

What they say about merits ?

• There is a widespread belief that a monolithic slab foundation is an absolute “panacea” for all cases, that is, it can be built on any type of soil. Allegedly, such a slab of a house, even in a marshy area, will be a reliable basis for a heavy building, since due to its “buoyancy” it will vibrate along with the movements of the soil, without being subject to deformation.

It is certainly impossible to agree with this statement. Most likely, it would be more correct to say only that a slab foundation opens up expanded possibilities for construction in areas with complex soils, with insufficient load-bearing capacity for a strip foundation, and with average heaving rates.

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

And a slab foundation, located almost 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 from below to the surface of the slab. 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 occurs to a shallower depth, and thawing in the spring occurs much faster. This means that the slab willy-nilly will experience colossal internal bending stresses.

As a rule, slab foundations have a very significant margin of safety, and perhaps the slab itself will withstand such loads without cracking, but small linear deformations are quite likely. They will certainly be transferred to the walls, and in addition, the tilt of the entire building from the vertical axis cannot be ruled out. 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, the lever of application of force. And it is possible that somewhere in the upper area of ​​the wall a crack will suddenly appear and begin to expand.

So, speaking objectively, you shouldn’t overestimate the versatility of a slab foundation – that would be reckless. In any case, if there is no confidence in unconditional success, it would be more advisable to invite specialists to conduct a geological analysis of the site. In addition, it is always useful to familiarize yourself with the “history” of the use of slab foundations in the nearby area - what kind of houses were built on them and how long ago, what is the depth of the foundation and the thickness of the slab, are there any complaints about the operation, how the buildings survived seasonal ground fluctuations - these and other questions will help you make the right choice.

• Slab monolithic foundations allow the construction of large, even multi-level houses built from heavy materials.

This is true, and many multi-storey buildings in large cities are built 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 development site, and high-quality execution.

So the common opinion that a slab foundation is suitable only for small compact houses, and that “its life is short-lived” 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 ground surface or with a slight recess, then this is indeed the case - only the top fertile layer of soil is removed, and the depth of the pit is largely determined by the calculated 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, plus insulated blind areas), then the volume of selected soil can still be considerable. So this advantage is not very 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 a corresponding pit, that is, it is very difficult to do without the use 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 preparing the slab for pouring, you provide a high-quality thermal insulation belt, then the floors will also be pre-insulated. In addition, in the “insulated Swedish stove”, water heating circuits for the floors are also immediately installed.

• Work on a slab foundation cannot in any way be classified as a task of an increased category of complexity.

An ambiguous statement, with which, nevertheless, one can agree to a certain extent. Indeed, the work itself on the stove does not involve operations that require the highest qualifications of workers. Digging a pit and compacting a sand and gravel cushion, knitting a reinforcement frame, installing formwork, pouring and distributing concrete, caring for a slab that is gaining strength and other stages - all this is either understandable from the beginning, or a novice craftsman can get the hang of it in a very short time.

Another thing is that a number of operations require the use of special tools and equipment. Thus, for high-quality compaction you cannot do without a vibrating plate; for the quick and uniform production 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 concrete to be poured can be considerable, and it is advisable to pour the slab in one day, it is hardly worth relying on - you will have to order it for delivery.

We can say that, provided that some operations involve outside forces and resources, the owner, who has enlisted the help of friends or relatives, can easily handle the bulk of the work. True, you need to be prepared for the fact that the work ahead will be quite long, physically difficult, and sometimes even tiresome and monotonous. But for a small team of several strong men, it is doable. Of course, with strict adherence to all technological recommendations.

It is interesting that in some publications devoted to slab foundations, this is presented not as an advantage, but as a disadvantage - they say that 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 is viewed.

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

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

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

The only exception may 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 upward-directed stiffening ribs - grillages, or well-thought-out reinforcement backfills, from which further construction of the buried part of the walls is already underway, by analogy with a deep strip foundation. But this type of foundation is a very expensive “pleasure” that requires highly qualified calculations and practical execution.

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

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 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 a considerable total area, centimeters very quickly grow into cubic meters of concrete solution. Two-tier reinforcement will require a significant consumption of reinforcement, certainly more than when pouring a strip base. However, we must not forget that, along with the foundation slab, the developer immediately receives a finished foundation - essentially, the subfloor of the first floor, with it already well-made, and sometimes with insulation. That is, these stages of work are already falling out of the overall estimate.

So the excessively high cost is not always an obvious drawback, and the simplicity of constructing the slab largely compensates for the increased consumption of building materials.

How to calculate a monolithic slab foundation

Any foundation requires calculations, and slab foundations are no exception in this regard. True, it should be especially noted that designing 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 yourself, for example, when constructing non-residential structures - a garage, barn, bathhouse, and utility buildings. And one of the key calculation parameters is always the thickness of the monolithic slab. Too small a thickness may not cope with bending loads; excessive thickening is a waste of effort and money.

How is the optimal slab thickness calculated?

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

This makes it possible to evaluate the composition and thickness of the layers, the presence of “overwater”, and the location of aquifers, on the basis of which further calculations can be made.

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 value 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 the 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 sufficiently objective.

When calculating the required slab thickness, it is better to use 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 value, with a possible deviation not exceeding 20÷25%.

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

Please note the following:

• The second table does not show all types of soils. The fact is that on soils with high load-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 color in the table. In both of these cases, it is recommended to conduct an in-depth analysis of the technical and economic feasibility of constructing a slab foundation.

— In the case of sandy loams, it is possible that the construction of a conventional strip foundation may be much more profitable.

— Hard clays are singled out for the reason that the density of their structure can sometimes be deceptive. If there is a possibility of waterlogging of these layers, for example, by nearby aquifers with seasonal fluctuations in their filling, then a sharp loss of the bearing capacity of the soil cannot be ruled out. The slab, along with the building, will gradually begin to “sink.” It is worth considering the question of the possibly greater feasibility of using

So, in order to calculate the required slab thickness, you will have 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” using 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 initial data, determine its optimal thickness. At the same time, do not forget to take into account that the slab must protrude beyond the perimeter of all walls outward by at least the amount of its calculated thickness or even more - this already depends on the features 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 calculation accuracy, but for “estimates” in the field of DIY construction it can provide a useful service.

The calculator assumes that the developer has design outlines for the future building, that is, it will not be difficult for him to decide on the initial data. You will need to know the material and area of ​​the walls (minus window and door openings), the area and type of floors, the area of ​​the roof and the steepness of its slopes (to take into account the snow load). The calculation program already includes average values ​​of the specific gravity of building structure materials, and takes into account approximate operational loads (weight of finishing, furniture, large household units, dynamic loads from people living in the house, etc.).

How to correctly calculate the area of ​​structures?

Since area values ​​often appear in calculations, it is worth giving appropriate recommendations in this regard. They are presented in a special article on our portal dedicated to it, which, by the way, also contains convenient calculators.

It is best to prepare the data necessary for the calculation in advance, write it down in a separate table, and then proceed with the calculations.

In practice, several foundation designs are used in construction. One of the most common is monolithic. In essence, it is a reinforced concrete monolithic slab laid to some depth in the ground.

Its difference from other types of foundations is that when groundwater rises or soil layers deform, the monolith located under the building will respond to changes as a whole, that is, with its entire mass. Such a reaction will not lead to deformation of the house.

A monolithic slab can be given any shape that will completely match the shape of the house. And the most important thing is that this design of the building’s base ensures complete tightness, since there are no structural joints, and the concrete itself is made using water-repellent additives.

In addition to the obvious advantages, the monolithic design also has some disadvantages. These include the large amount of time required for its construction. Pouring the slab itself will require a significant amount of concrete and the use of special equipment.

As already noted, a monolithic foundation is a slab laid in a previously prepared place. But, nevertheless, there are several ways to make such a base. They differ from each other in their hydro- and thermal insulation options. As you already understand, a monolithic strip foundation is a little different. There, the earth is dug up only for the foundation, if there is no basement, and the earth remains under the space of the rooms. Here the entire volume of earth is excavated, under the entire area of ​​the house.

The simplest of these types of foundations is performed according to the following scheme:

A reinforcement structure is installed at the bottom of the pit, on a pre-compacted sand cushion, and then filled with concrete. More complex ones include structures that use sheets of waterproofing material, geotextiles, and, depending on the type of soil, it is possible to make an additional cushion from crushed stone.

The most complex monolithic foundation looks like a multi-layer sandwich in cross-section:

• sand cushion;
• layer of geotextile;
• layer of crushed stone;
• the so-called preparatory layer of concrete;
• waterproofing layer;
• monolithic slab.

Sometimes, to increase the reliability of foundation protection, polystyrene sheets are laid before pouring concrete, thus improving the thermal insulation of the foundation.

Such complex structures are used on difficult soils, for example, with a high groundwater level. Builders with extensive experience say that a monolithic foundation can be used even in peat bogs.

To calculate a monolithic foundation slab you need to know:

• Groundwater level;
• Parameters of the soil on which the foundation will be placed;
• The amount of soil freezing;
• The total weight of the building, it includes the weight of the box, roof, furniture installed in it, household appliances and residents;
• Size of snow and wind load;
• The weight of the plate itself.

As a result of calculating the specified parameters, it is possible to determine what pressure the entire structure will exert on the ground. Then you need to refer to SNiP 2.02.01–83 and determine the maximum pressure on the ground at the building site. Let's look at an example:

• The weight of the building is 19 tons;
• Roof weight 3 tons;
• The weight of the foundation slab is 20 tons.

Possible snow and wind loads will add 7.5 tons on top, for a total load of 49.5 tons.

With a building size of 6x6 meters, the surface area of ​​the foundation will be 36 square meters or 360,000 square centimeters. The load on the ground will be the difference between the weight of the structure and the area of ​​the foundation, resulting in 0.13 kg per square meter. centimeter. This load is acceptable for any soil.

When calculating the thickness of the monolith, it is imperative to take into account the following parameters:

• Distance between layers of reinforcing mesh;
• The height of the concrete layer on and under the outer layers of the reinforcing mesh;
• Reinforcement dimensions.

Practice shows that the traditional slab thickness is 200–300 millimeters. If we take into account that under it there should be a compacted sand cushion with a total height of up to 300 mm, then the thickness of the composition is 600 mm. It is necessary to understand that this parameter changes depending on the type of soil and the weight of the building.

In addition to the power calculation of the structure, it is necessary to calculate the amount of consumables and reinforcement.

The volume of concrete is equal to the product of the perimeter of the foundation and its height, and the required volume of sand or crushed stone is calculated in the same way. Based on the calculations carried out, the required amount of waterproofing, reinforcement, etc. will be known.

Direct construction of a monolithic foundation

Stage I. Site preparation

Preparatory work for the construction of a monolithic foundation begins with cleaning the surface of the construction site. Everything unnecessary is removed from it, including the turf on which the grass cover is located. After this, you can mark the future pit. It is advisable to start marking from the wall that will be parallel to the fence.

For marking, you will need a cord that does not stretch, several pegs. If you don’t have special geodetic tools at hand to use for marking, you can do it yourself. It is necessary to prepare several pieces of cord in advance; their length should be equal to the length of the wall and the allowance for securing it to the peg.

After you have marked the first wall using a cord and pegs driven into the ground, you need to tie the piece of cord that will mark the second wall to one of the ends. To form between them, the developer must solve the Pythagorean Theorem, this will allow us to find out the length of the diagonal between the walls.

By moving the cords you need to build a right triangle. Once it is built, you can begin marking the remaining walls. The result will be a rectangle that indicates the location of the future foundation. You can check the quality of the markup quite simply. It is necessary to measure the diagonals; if everything is marked correctly, then their sizes will coincide.

After marking is completed, excavation work begins. The main requirement for the quality of their implementation is the following - the bottom of the pit must be located strictly horizontally, look at the photo.

This determines the quality of the foundation being built. If we take into account that the depth of the pit lies within 1 meter, then the developer has a choice: to dig it manually or invite special equipment. In any case, after the main volume of soil has been removed from the pit, it is necessary to level the bottom and, as soon as it is found, remove all excess from it.

After the foundation pit is ready, it is necessary to arrange a cushion, as noted above, it can be made of sand or small crushed stone. The height of the cushion is up to 300 mm after compaction.

By the way, before you start pouring sand, it is advisable to lay geotextiles at the bottom of the pit; it will prevent sand from penetrating into the soil surface. For this operation, it is advisable to use a special vibrating rammer.

As the sand compacts, it is necessary to constantly add fresh sand and continue to compact it until the desired height of the cushion is reached. The surface of the pillow should be located in a horizontal plane.

Stage III. Installation of formwork

Any work related to the manufacture of reinforced concrete structures is, in one way or another, related to the arrangement of formwork. The simplest formwork is wooden panels knocked down from boards. The boards are attached to vertical bars.

These boards must be installed vertically and secured with wooden braces resting on a peg driven into the ground. The step between them is about 1 meter. But practice shows that the more often they are driven into the ground, the stronger the formwork will be.

It is advisable to protect a full-fledged monolithic foundation from moisture and ensure its thermal insulation. To achieve waterproofing, ordinary roofing felt is used, which is laid in two layers or on the surface of the cushion if a simple monolith is being constructed, or laid before pouring on a layer of intermediate concrete.

Thermal insulation of the foundation, if necessary, is constructed from polystyrene foam. A layer of insulation is laid in front of the concrete layer and a polyethylene film is placed on top of it.

The reinforcement structure is made on a sand bed. It consists of two belts. For reinforcement, reinforcing mesh may be used, but this only applies to foundations for small structures, for example, a bathhouse.

To build a full-fledged foundation, it is advisable to use corrugated reinforcement with a diameter of 10 mm or more.

For vertical rods, it is permissible to use smooth reinforcement with a diameter of 8 mm or more. We must remember that the heavier the building, the larger the diameter of the reinforcing bars.

Vertical reinforcement is driven in in increments of 200–300 mm over the entire area to be poured with concrete. The bottom layer of reinforcement should be located at a distance of about 50 mm from the surface of the pillow, and the top layer at a distance of 50 mm from the surface of the foundation. The reinforcement is connected to each other with knitting wire or plastic clamps.

Pouring the foundation is essentially a finishing operation, and experience suggests that to carry it out, it is advisable to order concrete from the nearest plant and deliver it using a mixer. Thus, it will be possible to carry out pouring from several points, and leveling it will be much easier. By the way, you must always remember that the concrete being poured must be compacted. To do this, you can use special submersible or surface vibrators.

Video

Watch a video about building a monolithic slab foundation for a house with your own hands.

It is difficult to imagine the construction of buildings without the installation of concrete floors. Reinforced concrete panels manufactured at enterprises are often used. To install them, it is necessary to use special lifting equipment. Modern technology allows you to build a monolithic floor with your own hands without the use of lifting devices. Let us consider in detail the design features and manufacturing technology of a solid floor, which is superior in terms of a set of indicators to a structure made from standard slabs.

When building any individual two-story residential building, the question arises of how to make the interfloor ceiling

Why is a monolithic base superior to the installation of hollow core slabs?

The pouring of a monolithic floor and the technology of laying floor slabs manufactured at reinforced concrete enterprises are aimed at forming a strong reinforced concrete base that serves as the floor of the upper floor and the ceiling of the lower. However, a solid interfloor slab is superior to a prefabricated structure in a number of respects.

The main advantages of a monolithic base:

• increased safety margin associated with the absence of joining seams in a solid reinforced concrete structure;
• uniform transfer of existing loads to load-bearing walls and foundations;
• the ability to implement non-standard layouts and original solutions for which it is difficult to use standard slabs;
• ease of implementation of design solutions related to the construction of remote balconies on a cantilever slab;
• impossibility of displacement when installing a solid interfloor base in the longitudinal and transverse directions.

One of the main advantages is the absence of the need to use special lifting equipment to lift massive reinforced concrete slabs, as well as the ability to carry out installation activities on your own.

How to make a floor slab with your own hands - rules for laying prefabricated slabs

Standard reinforced concrete panels are reinforced with a reinforcement cage and do not require the installation of formwork. At the same time, despite the apparent ease of installation work, before starting construction activities, you should carefully familiarize yourself with the rules for installing solid slabs.

Observe the following requirements when laying panels on solid walls:

• pay attention to the distance between the end planes of the load-bearing walls, which does not exceed the maximum length of the finished slab (up to 9 meters);
• use lifting equipment to remove and transport slabs to the work site;
• securely fasten the rigging equipment to the loops or special sling eyes built into the concrete mass;
• carry out installation on the planned end plane of the walls, and you must ensure that they are evenly laid;

• support the reinforced concrete panels on the walls, ensuring an equal amount of overlap. The slabs should be located 90-150 mm away from the edge of the wall;
• carefully seal technological gaps and butt seams with cement mortar, do not allow installation without cementing;
• control the horizontalness of the surface during installation using a building level and plumb line;
• carry out installation only on the surface of main walls, construct internal lintels and partitions after installing the slabs;
• cut openings and interfloor hatches only in the area where adjacent concrete panels are joined;
• provide a guaranteed three-millimeter gap between the side planes of reinforced concrete slabs.

If the overall width of the precast panels does not match the distance between the walls, lay them with an even gap or leave gaps on the sides and then seal them with concrete blocks or mortar.

When concreting the gaps, attach a shield to the underside of the slabs to allow the mortar to be poured.

The quality of installation work depends on the correct implementation of preparatory measures.

Observe the following requirements:

• ensure the flatness of the ends of the main walls, eliminate unevenness using cement mortar;
• make sure that the load-bearing walls have a safety margin, strengthen them, if necessary, with a reinforced belt;
• fasten the support rods in 1.5 m increments to secure the slabs during installation.

Perform installation using lifting equipment according to the following algorithm:

1. Place a layer of mortar on the end of the walls.
2. Sling the slab by the eyes.
3. Give the command to the crane operator to move the panel.
4. Lower the slab, maintaining a distance of at least 120 mm on each side.
5. Check the correct position and disconnect the straps.

Remember that horizontal installation is ensured only by a layer of concrete without using steel reinforcement and various elements as a backing. At the final stage of the work, anchor the slabs with steel reinforcement or a ring anchor. Then the joining seams should be sealed with cement mortar, and the internal cavities of the slabs on the end sides should be filled with mineral wool or cement mortar 30 cm on each side.

Calculation of the load on a monolithic floor

During operation, a monolithic floor is exposed to various loads:

• permanent. They are transmitted by the mass of the building walls, internal partitions, as well as the weight of the building’s roof structure, which absorbs the additional influence of snow loads and wind;
• temporary. Their size is related to the mass of utilities, suspended ceilings, floor finishing, furniture, as well as the number of people in the room.

The magnitude of the perceived load is determined by the thickness of the reinforced concrete floor. Thus, with a thickness of a monolithic slab of 20 cm, each square meter of surface can accommodate up to 0.5 tons of payload.

Correct calculations will allow you to evaluate the load capacity of a reinforced concrete slab, taking into account actual operating conditions, and also avoid the formation of cracks.

The accuracy of calculations is influenced by a complex of factors:

• overall dimensions of the ceiling;
• thickness of the reinforced concrete slab;
• brand of concrete used;
• the value of the calculated load per square meter of flooring.

Calculations make it possible to determine the diameter of reinforcing bars that absorb bending and tensile loads. To perform calculations yourself, you must master the calculation methodology. When planning to build a monolithic floor with your own hands, it is advisable to entrust the calculations to professionals or use an online calculator.

How to pour a monolithic floor slab - technology for performing the work

After performing calculations and determining the parameters of the reinforced concrete slab, you should prepare building materials, as well as the necessary tools.

The technology for forming a solid reinforced concrete slab involves performing the following work:

1. Production and installation of panel formwork.
2. Assembly of the reinforcement frame.
3. Preparation of concrete solution.
4. Filling the formwork with concrete mixture.

Let us dwell on the features of each stage.

How to install formwork for a monolithic floor

To make a formwork structure, prepare:

• moisture-resistant plywood up to 25 mm thick, covered with laminate. The smooth surface of the plywood will make it easier to remove the panels after the concrete has hardened;
• planed boards made of durable types of wood. Make the lower shield from a board 50 mm thick and up to 200 mm wide;
• wooden logs with a diameter of 120-150 mm or standard telescopic supports. They are designed to fix the formwork structure;
• boards or beams used as transverse beams of formwork. The cross members support the prefabricated panel frame.
• hardware and a standard set of tools, including a saw for cutting wood, a hammer and a building level.

The technology involves the formation of a reinforced concrete mass using the formwork method. To cover the ceiling, the formwork is installed with your own hands according to a simple algorithm.

Procedure:

1. Mark the level of the formwork on the surface of the walls.
2. Install vertical beams, logs or supports in 1-1.2 m increments.
3. Secure cross bars or metal profiles into the support forks.
4. Lay sheets of plywood or planed boards without gaps and secure them.
5. Secure the vertical walls around the perimeter of the wooden formwork.
6. Check the levelness of the surface and the tightness of the corner areas.

Dismantling of the formwork is carried out a month after pouring concrete.

Reinforcing reinforced concrete floors - we reinforce reinforced concrete floors with our own hands

To strengthen the overlap you should prepare:

• linings for reinforcing bars. Clamps are installed to ensure a constant distance between the frame and the concrete surface;
• rods with a cross section of 12-18 mm and annealed wire for tying reinforcement. A crochet hook will speed up the connection of elements.

You will need a device for bending rods, as well as a grinder with a circle for metal.

When assembling the reinforcement cage, follow the given sequence of operations:

1. Cut the reinforcing bars into pieces of the required sizes.
2. Tie the rods with wire, forming a mesh with cells 15x15 or 20x20 cm.
3. Place the bottom mesh on the supporting elements.
4. Install vertical bars in 1 m increments.
5. Assemble the top tier of the frame and attach it to the vertical rods.

When assembling the reinforcement cage, pay attention to the amount of overlap, which is 35-40 times greater than the cross-section of the rods.

Preparing concrete for a monolithic floor

When thinking about how to pour a monolithic floor with your own hands, determine the composition of the concrete solution to be poured.

Concrete for monolithic flooring is prepared based on the following components:

• cement grade M400;
• crushed stones up to 20-30 mm in size;
• sifted sand;
• water.

The standard recipe involves mixing sand, crushed stone and cement in a ratio of 2:1:1. The amount of water added depends on the moisture content of the ingredients. Water is added until the solution reaches a creamy consistency.

It is convenient to mix in a concrete mixer. First, mix the dry ingredients and then gradually add water.

Concreting a monolith - pouring a monolithic floor on your own

To ensure the strength and uniformity of the reinforced concrete surface, it is necessary to pour a monolithic floor slab in one step. Given the increased need for concrete, it is advisable to purchase a ready-made solution delivered in a construction mixer.

Filling the floors with your own hands is carried out according to the following algorithm:

1. The concrete solution is fed into the formwork and distributed evenly over the entire area.
2. Compaction is carried out using a deep or surface vibrator.

After compaction, the surface of the massif is leveled, hardening for four weeks.

Hardening of a monolithic floor slab - taking care of concrete

The normal course of the hydration process requires periodic wetting of the concrete. When concrete hardens, a significant amount of heat is released, which promotes the evaporation of water. Lack of fluid causes cracks to appear.

It is necessary to maintain the humidity of the array as follows:

• lay polyethylene on the surface;
• Moisten the concrete periodically.

It is important to prevent the concrete from drying out and cracking.

Having mastered the technology of performing the work, it is not difficult to make a monolithic ceiling with your own hands. Using a proven method, it is easy to produce solid, as well as interfloor ceilings of a foam block house. When deciding, use ready-made panels or pour a monolithic reinforced concrete slab. If done correctly, it will serve as a reliable foundation for the walls of the building. Use high-quality concrete for pouring, made according to a proven recipe.

It is economically justified to install a slab foundation if the bearing capacity of the soil in the building area is unsatisfactory, the groundwater level is high, and the content of clay that swells when frozen is high. Constructing a slab with your own hands is possible on a flat area with a guaranteed absence of third-party communications.

When pointing out the main disadvantage of a slab foundation - its high cost, opponents of this technology do not take into account that the slab is also a ceiling, a floor on the ground, and allows the integration of a heating system into it. This, ultimately, is cheaper than a deep strip base; the amount is quite comparable to MZLF with a safety margin of 300%.

The diagram of a slab protected from frost heaving in a private house looks like this:

• sand – 15 – 20 cm, replaces heaving soil;
• crushed stone – 15 – 20 cm, is the drainage layer;
• communications – necessary for life support systems;
• drainage - laid around the perimeter, collects water from the ground, removes it from concrete structures;
• concrete preparation - thickness 5 - 10 cm, used as a rigid base for rolled waterproofing, which in its absence will be torn by the sharp corners of crushed stone;
• waterproofing - two - three layers, roll materials on a polyester, fiberglass base are recommended (Tekhnoelast, Linokrom, Bikrost), the layer protects the concrete structure from moisture;
• thermal insulation - 15 - 30 cm, retains the geothermal heat of the subsoil under the base of the house, heaving soil does not freeze, there are no heaving forces;
• stiffening ribs - increase the strength of the slab, are made across the long wall of the house and along the perimeter, directed downwards from the sole;
• reinforced belt - two reinforcing mesh with a cell of 20 x 20 cm made of rods 12 - 16 mm;
• heated floor - water circuits laid on top of the fittings or between the grids;
• concrete – thickness 20-50 cm, ensures rigidity and strength of the slab;
• flanging - made of polystyrene foam, protects the slab at the ends;
• insulation of the blind area - sheets of expanded polystyrene increase the perimeter of thermal insulation, cutting off lateral freezing.

The main advantages of a slab foundation are:

• lack of special equipment - all work can be done with your own hands;
• minimal soil excavation - it is enough to remove the fertile layer.

The main costs are for reinforcement, insulation, waterproofing and ready-mixed concrete, which is best ordered to ensure that the formwork is filled in one go.

Step-by-step instructions for installing a slab foundation

Step-by-step diagram of the slab base installation

Surveys and calculations

Taking soil samples

When designing a monolithic slab, it is necessary to take into account the experience of similar structures in the region, the results of surveys (ground level, nature of the soil, bearing capacity of the layer), conditions of the technical specifications (number of storeys, wall, roofing materials). The survey includes a minimum of five geological pits (corners + middle of the slab).

The result of the research is the characteristics of strength, deformation of different layers of soil in the building area, prediction of changes in the chemical composition during the operation of the home, and the degree of aggressiveness of groundwater.

It is necessary to compare several solution options to identify the best combination of construction budget and technical characteristics. Step-by-step calculation instructions:

• concrete grade – M200 and higher for slabs, M50 for preparation, according to the foundations of structures, buildings;
• groundwater depth – anti-corrosion measures in the presence of high water;
• when calculating prefabricated loads, the weight of the slab on sandy soil is not taken into account;
• The load-bearing capacity and deformations that can destroy the structure are calculated.

For this purpose, special programs are used that have proven the performance of foundations manufactured based on their results in real operating conditions. The main documents at this stage are:

• soil classification - ;
• enclosing, load-bearing structures –;
• anticorrosive structure of the building's load-bearing frame -;
• design, manufacturing of MZF – .

Unlike strip foundations, the slab has an increased support area, prefabricated loads from the building are distributed evenly, and the strength margin is very large.

Marking and excavation work

Removing the fertile soil layer

It is forbidden to pour the slab over the fertile layer. The house layout diagram looks like this:

• axes - are carried out in the building area with a cord attached to pegs installed beyond the perimeter of the drainage system;
• the pit is 0.5 meters larger than the slab on each side (for drainage), the slab protrudes beyond the dimensions of the building by at least 10 cm (depending on the project).

Due to the small amount of work required to remove the fertile layer (20–40 cm) for a residential building, the work is carried out with one’s own hands without the use of special equipment. At this stage, it is necessary to ensure protection of the monolithic structure from soil moisture (overwater). To do this, drains are laid around the perimeter:

• geotextiles extending to the edges of the ditch;
• layer of compacted crushed stone;
• perforated pipe (corrugated or smooth in a dornite filter) with a slope towards the underground tank;
• backfilling with a natural filter (crushed stone fraction 10/20);
• covering with the remaining geotextile.

Drains must not be installed under a concrete preparation or foundation slab. The height of the backfill should be level with the crushed stone base cushion.

In addition, after pouring the slab into the building, it is impossible to enter communications, so cold water and sewage pipelines are laid at the same stage. They do not have to be buried below the freezing mark, since the thermal insulation of the base of the slab will retain geothermal heat and the ground under the cottage will not freeze. A depth of 1 - 1.2 m is sufficient.

Substrate

We arrange a sand cushion. Sealing is required.

Another measure to reduce heaving forces is the substrate. It is made by hand using the following technology:

• layer-by-layer compaction of sand - 10 cm backfill, abundant moisture, compaction with a vibrating plate, a second layer of similar thickness;
• layer-by-layer compaction of crushed stone - fraction 10/20, similar.

Lay a layer of crushed stone.

Instead of crushed stone or sand, a mixture of ASG can be used to a depth of 40 cm with compaction using the specified method. Only in this case will the monolithic foundation of the house receive reliable support on the lower layer.

Concrete preparation and waterproofing

We do concrete preparation.

A monolithic slab requires a lower waterproofing cutoff to prevent corrosion of the concrete and reinforcement inside it. Laying a waterproofing carpet made from roll materials over a layer of crushed stone does not satisfy the operating conditions:

• sharp edges of stones cut through the material;
• the seams cannot be properly sealed.

Therefore, when building the foundation of a house with your own hands, concrete preparation is often used. This is a regular screed that solves two problems:

• providing a flat surface on which it is easy to stick the bitumen base of Bicrost, Linokrom, Technoelast, and reliably seal the seams;
• creating a level base for the slab, strengthening its strength, and stabilizing its geometry.

We install waterproofing.

The method of pouring into the formwork is standard, the thickness of the screed is 5 cm, no reinforcement is required. Roll materials provide a minimum construction budget, impregnation, primers are not used here. The recommended overlap of the strips is 15 - 20 cm, the seams are treated with hot or cold bitumen-based mastics. The edges of the waterproofing carpet extend beyond the perimeter of the concrete preparation so that after pouring the slab, they can be launched onto the sides and top surface.

We lay insulation under the entire area of ​​the building.

Extruded polystyrene XPS is used as a heat insulator. It is laid in two layers (10 + 10 cm) close together for smooth slabs. If the project provides for stiffening ribs, the first layer is laid end-to-end with your own hands, in the second layer gaps are created along the width of the ribs:

• along the perimeter;
• perpendicular to the long wall after 3 m.

In this case, the monolithic slab has a large margin of safety, and the house is free from distortions during operation.

Reinforcement

We create a reinforcement frame in accordance with the project.

Reinforcement of the slab with reinforced belts is carried out in accordance with the regulatory documentation for reinforced concrete and concrete structures. The reinforcement scheme looks like:

• production of clamps - a smooth 6 mm rod, bent in the form of a square or triangle;
• creation of reinforcing mesh - longitudinal, transverse bars of a periodic profile with a diameter of 12 - 16 mm, connected with knitting wire or connected by welding (cell 15 x 15 cm);
• reinforcement of stiffeners - four longitudinal rods connected with clamps;
• laying the lower chord - installed on concrete pads (thickness 15 - 25 mm, section 10 x 10 cm) to provide a protective layer (the reinforcement must be recessed in the concrete);
• installation of the upper belt - clamps are placed on the lower mesh, and the upper card is attached to them.

The slab is reinforced at the ends with U-shaped clamps.

It is not advisable to use separate rods inside the armored belt. They need to be bent in curved sections, in places where communications enter nodes with common grid maps. To save reinforcement, the cell in some cases is enlarged to 20 x 20 cm.

Formwork

We install and strengthen the formwork.

To fill a monolithic structure with your own hands, you need to install formwork around the perimeter. It is constructed from OSB, chipboard, plywood or edged boards in the form of panels. The inner surface is sheathed with roofing felt or film to prevent concrete from spalling during formwork removal. The main document for the construction of formwork are standards; .

The panels are mounted around the perimeter; to protect the structure from freezing, 10 cm of polystyrene foam can be placed vertically inside them. This insulation is also laid under the blind area of ​​the house to prevent lateral freezing. It is laid at the level of the base of the slab, flush with the bottom or top layer of heat insulation inside the formwork.

Pouring and maintaining concrete

Pour concrete into the formwork and level the surface. Sealing is required.

Requirements for the design and manufacture of MZF are specified in the standards according to which the work is carried out. When filling, the following conditions must be met:

• filling the formwork with concrete in one step;
• the maximum interval between feeding the mixture with a mixer after vibration compaction of the previous section is 2 hours in warm weather;
• It is forbidden to move concrete with shovels along the entire perimeter from one place - it is necessary to rearrange the mixer or use a concrete pump;
• vibration compaction is carried out until cement laitance appears, crushed stone is hidden and there are no bubbles;
• the step of lowering the nozzle of the deep vibrator cannot exceed its radius of action;
• in winter, the mixture is heated with a cable laid inside the formwork, covered with film materials, and heated with steam;
• vibrator attachments are prohibited from leaning against the mesh of armored belts;
• stripping is possible on the fifth – seventh day under normal conditions;
• The surface of the concrete must be protected from precipitation, covered with burlap, and wetted from a watering can in hot weather.

If technologies, recommendations for the selection of materials, and reinforcement sections are followed, the slab foundation will not require restoration and will serve at least three generations of property owners. All of the above technologies comply with the requirements of the specified regulatory documents and have operating experience in the regions of the Russian Federation.

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