Concrete preparation for the foundation - SNiP requirements and installation of concrete footings. Why is concrete preparation necessary for the future foundation? Footing or sand cushion for the foundation

The stability of foundations depends on the quality of foundation preparation. Its choice and design are largely determined by the material of the underground structures and the soil conditions of the development site. Concrete preparation for the foundation is considered the most reliable and expensive compared to sand and crushed stone pads. Most often, it is performed under monolithic strips and slabs, taking into account the requirements of the relevant SNiP and SP.

Why do you need a footing?

First of all, preparing the site for the foundation is aimed at strengthening and leveling the foundation. But the concrete layer is also a barrier that protects the future underground monolith from the loss of cement laitance, which, when concreting the structure, can simply seep into the ground or underlying layers of crushed stone and sand. The footing helps retain moisture in the mortar mass, which is required for the correct completion of the concrete curing process. If there is not enough water, the cement will not be able to fully reveal its properties, and this will lead to:

to the appearance of cracks in the concrete structure;
to a lack of design strength;
to further destruction of the foundation during operation.

The installation of a concrete platform at the base of the underground part of the house in accordance with SNiP promotes the most uniform distribution of loads acting from the soil and the ground part of the structure. Preparation for a concrete foundation allows you to level the bottom of the excavation and stably position the reinforcement cage for a monolithic strip or slab in the formwork. In addition, the underlying layer practically eliminates the occurrence of soil shrinkage due to the influence of large or point loads.

Another reason that determines why a footing is needed is that, based on a hard and even preparation layer, the construction of the foundation in winter period it happens easier.

Regulatory documents - SNiP and Code of Rules (SP)

The construction of any structures during the construction of civil and industrial facilities is subject to certain requirements specified in the relevant SNiP and other standards of state and industry significance. Concrete preparation for the foundation is carried out based on:

SNiP 2.02.01-83;
SP 63.13330.2012;
SP 50-101-2004.

These documents define measures for the design and installation of foundations, taking into account:

soil type;
surrounding buildings;
effective loads;
seismicity;
environmental requirements.

The thickness and width of concrete preparation for the foundation is calculated, according to SNiP, according to bearing capacity and possible deformations. In the first case, calculation is required if:

significant compressive loads are expected;
the structure is supposed to be located near slopes, on a slope or embankment;
There are weak soils under the base of the foundation.

It should be noted that SNiP allows not to carry out calculations of bearing capacity if the project provides for measures that exclude soil displacement for the previously mentioned reasons.

All long-term and short-term forces transmitted from the structure, including the weight of the underground part of the structure, are taken as loads on the concrete preparation of the foundation. Possible combinations are indicated in SNiP.

Construction of the footing

Regardless of the type of soil, at the first stage of preparation of lean concrete for the foundation, the bottom of the excavation should be leveled. For your information, for a monolithic tape it will be enough to dig a trench, but for a slab you will need a foundation pit. When determining the excavation depth, the thickness of the concrete base and the thickness of the sand and gravel layer laid directly on the ground are taken into account.

Loose soil must be compacted, and sand and crushed stone must be added to the bottom of the excavation. The layers are also compacted. Crushed stone, in this case, will perform a drainage function. Next, roofing felt sheets or films are laid on the surface as waterproofing.

Concrete preparation for a monolithic strip or foundation slab should protrude along the perimeter beyond the underground structure by 10-15 cm. Taking this into account, a crushed stone-sand base is made and formwork is installed for pouring the base. The height of the box is taken based on the thickness of the preparation for the foundation.

At the next stage, a lean concrete solution is mixed, which contains a small volume of cement. Gravel and sand are used as filler. After the concrete is poured into the formwork, it will need to be compacted to get rid of air bubbles and leveled. In the first few days, the surface of the concrete preparation is covered with plastic film, preventing excessive drying of the surface.

It is important to know that the foundation base, which is not reinforced with reinforcement, has size limitations.

Reinforcement significantly strengthens the footing and increases the reliability of the underground part of the structure. The nets are knitted using wire from rods with a diameter of eight millimeters, and laid before the solution is poured. To ensure reliable coupling of the concrete preparation with the foundation, metal rods are installed vertically into the thickness of the base so that they protrude 20-30 cm above the concrete surface.

The optimal thickness of the concrete base without reinforcement is considered to be 15-20 cm. When installing a reinforced concrete base for the foundation, the size of the preparation can be reduced to 6-10 cm. SNiP specifies the maximum deviation of the horizontal surface - no more than 5 mm per meter when installing a monolithic strip and no more than 50 mm for a slab more than 25 meters wide.

The difference in the quality of the foundation of houses depends not only on the materials used for construction, but also on how the site was prepared before construction began. When building a house, you need to decide whether it is suitable concrete preparation under the foundation, as the highest quality and most stable, or is it better to choose another soil for this soil. Sand or crushed stone preparation is less reliable, more difficult to create, but cheaper in building materials and installation time.

What is preparation used for?

Most often, concrete preparation is used for a poured foundation or to increase the strength and stability of the foundation of a house.

Reasons to make a concrete footing:

Additional waterproofing, which slows down the rise of moisture from the soil into the foundation.
A level construction site, removes any unevenness left when digging a pit by equipment or builders, allows you to level out differences of up to 10 cm.
Prevents the absorption of “concrete milk” into the soil, due to the fact that the concrete pouring is not done on open ground, and on a solid base, the base, when hardened, has the same density, which increases its performance.
Facilitates the installation of reinforcement, makes it possible to use clamps, protecting the base reinforcement from corrosion.
Eliminates bending of reinforcement due to pressing into the ground under the weight of uncured concrete.

What types of preparations are there?

When preparing a site for a monolithic or strip foundation, you can choose different materials depending on required characteristics, budget and difficulties in installing on your own. The main reasons to choose one option or another are the endurance of the soil, its moisture content, and whether a basement or a basement is planned. It is also important what type of support will be used, not recessed, shallowly recessed or recessed. From what materials and in what way will it be built, poured or from ready-made blocks, strip or slab.

Unfortunately, SNiP 52-01-2003 and SP 50-101-2004 do not give clear recommendations in which case and what kind of preparation to carry out, so the reason for the choice is the type of foundation and the materials used for it.

Sand preparation

The simplest and cheap way level the ground for construction, this is sand preparation for the base, for light wooden houses used quite often, but not suitable for houses with a design life of more than 10 years. It is unreliable; gradual mixing with the soil and germination of plant roots causes subsidence under the weight of the building, and distortions and cracks of floors and walls are possible. Low moisture resistance requires additional waterproofing to prevent dampness in the premises.

Concrete preparation

“Lean” concrete is used with a maximum of 6% cement content, the main filler of which is sand, sometimes crushed stone or gravel. Pour a thin layer over the entire area of the future foundation, the thickness of the concrete preparation depends on the type of soil, the weight of the house and the level of burial groundwater. Depending on these three factors thickness can be from 4 to 10 cm.

Preparation with profile membranes

A new way to prepare a foundation, easy to install and less expensive than concrete or crushed stone. Despite manufacturers' assurances of strength and similar durability, it is in less demand.

If possible, proven concrete footings are often chosen. Because of additional expenses for thermal insulation, the cost can reach the price of standard preparation.

Crushed stone preparation

Crushed stone preparation for the foundation is used if reinforcement or uneven weight distribution is not provided. Crushed stone is poured with a thickness of 15 to 20 cm, filling it with bitumen until a film forms or the layer is completely saturated. For heavy houses it is unreliable due to the heterogeneity of the crushed stone and can lead to warping and cracks in the foundation and walls.

In the cold season, crushed stone preparation is almost not used due to the difficulty of creating the required temperature for bitumen pouring.

Preliminary work before pouring the concrete base

The construction of the foundation and preparation for it begin with geotechnical work to find out how deep the groundwater lies and what pressure the earth can withstand at the site of the future house. A construction plan is drawn up and the type of foundation is selected, monolithic or strip, poured or prefabricated.

Before creating a concrete pad, you need to mark the area in order to dig a pit. It should make it possible to make formwork for pouring, so an indent of at least 30 cm is made on each side of the future support.

The fertile layer of soil is removed and transferred to another place where it can be used. The depth of the foundation pit should be at least 20 cm greater than the planned height of the support.

If thermal insulation is installed, the depth of the pit is increased by the width of the additional layers.

Method for preparing lean concrete

Skinny concrete is called because it is very little content cement, which, due to its fragility, makes it useless for full-scale construction, but ideal for concrete preparations for the foundation. Depending on durability, the choice is provided by 2 classes of concrete mixtures, these are B7.5 and B15, the latter is more difficult to use due to the high content of expanded clay.

To obtain a cubic meter ready solution from B7.5 you need:

160 kg of cement is 6.4 bags of cement weighing 25 kg each;
2.2 tons of sand;
75 liters of water.

All ingredients must be mixed well and poured onto the prepared area.

When making B15, special equipment is needed to obtain a uniform consistency of the finished mixture.

Footing for a monolithic slab

10 cm of crushed stone or sand is poured onto the cleaned space and compacted using a vibrating plate. This is done to remove excess moisture from the base, making it last longer.

Formwork is mounted on the crushed stone cushion, into which a concrete mass of B7.5 cement will be poured. The formwork is made at such a height that the poured concrete forms a level top on which the foundation of the house will be laid. It must be a minimum of 10 cm and a maximum of 30 cm in height.

Often, when installing formwork, it is recommended to install concrete preparation for the foundation with an area reserve of 10–30 cm relative to the foundation. This is done in order to reduce pressure on the ground and leave space for thermal insulation and finishing work, which prevent the destruction of the foundation from the walls.

Concrete is poured flush with the top of the formwork, leveled and sometimes compacted using a vibrating plate. For better adhesion to the poured foundation slab, rods 0.8 cm in diameter are installed in the footing, protruding 10 cm from the preparation; if the base is planned to be large, then the footing will have to be poured in parts in order to insert the connecting reinforcement.

If a ready-made concrete slab is purchased and not poured, then the rods are not installed.

The layer of thin concrete is then left to dry for 7–21 days depending on the weather. Sometimes for heavy buildings the substrate is reinforced with a mesh with reinforcement 0.8 cm in cross section. In addition, the size of such a substrate must be at least 15 cm.

If the connecting rods were not installed in the substrate, then it is recommended to lay layers of waterproofing, thermal insulation made of EPS, and then waterproofing again on the finished flooring. After this, you can install the formwork for pouring monolithic slab basics.

How concrete preparation is poured and insulated can be seen in the video:

Footing for strip base

Concrete preparation for a strip foundation differs from preparation for a slab. They dig a trench that is 40 cm wider on each side of the foundation strip. Level the bottom of the trench and lay waterproofing. Formwork with a height of 20–30 cm is installed and the concrete mixture is poured.

The width of the concrete strip should be 15 cm greater than the base on each side. If you plan to use a poured strip foundation, the concrete footing is reinforced with rods for better adhesion.

When a buried strip base is built from ready-made blocks, it is advisable to use a preparation made of crushed stone impregnated with bitumen, compacted with a vibration plate. Sometimes waterproofing is placed on top and a second layer of concrete is poured for better resistance to damage.

With a shallow or shallow foundation on stable soils, leveling with sand or compacted crushed stone without bitumen is possible. Due to the lightness of the building, such a foundation does not require serious strengthening.

Preparation for a columnar foundation

For pile foundations, sand preparation is more often used due to the functions of the foundation itself. It is installed for light houses and on stable soils. Most often, it does not require additional amplification. If the house under construction is heavy enough, then crushed stone filled with bitumen is used. Concrete substrate is used extremely rarely, due to the opportunity to buy small concrete slabs, which are more reliable than poured ones.

Whatever the foundation and the house, in most cases concrete preparation will extend the service life and, spending money during the construction phase, will prevent spending on more expensive foundation repairs.

Laying the foundation is one of the most important components construction work. Not least important in this process is the construction of a special concrete footing, which should be located under a solid foundation. The quality of its execution determines the stability and durability of the structure. Before carrying out work, it is necessary to determine what density of concrete or crushed stone layer is needed for the construction of a particular building.

Definition

The footing is a layer of concrete mortar that must be prepared for the economical, convenient laying of the main foundation. This thin layer poured to the bulk (for example, during installation of the base using concrete slabs).

Purpose and thickness

A preparatory concrete or crushed stone base is made using different methods, funds and building materials. But with any device, its purpose will remain the same - it consists in preparing and leveling the surface. Due to this, the main concrete pour is consumed more economically due to uniform placement, which does not require additional consumption of the mixture for unevenness and depressions in the ground. Concrete and crushed stone footing, which is required for construction work, is used in the following cases:

Surface preparation for easy installation of structural parts. On a leveled site it is much easier to do markings, reinforcement cages, etc. Obviously, this work is more difficult to carry out on loose soil.
Waterproofing. Thin concrete bases are also necessary in order to retain moisture from the poured solution. Cracks appear on the frozen slab. They often appear due to the fact that the liquid is unevenly distributed in the cement structure.
Protection of the foundation from groundwater. If the layer is laid under a slab base, groundwater may enter the pit. In these cases, the footing absorbs part of the liquid, thereby preserving the load-bearing layer on which the building rests.

In addition, the presence of shock absorption increases the strength of the structure due to the fact that the base is better preserved. As for the thickness of the foundation monolith, it will depend directly on the dimensions and weight of the structure. On average, this figure is in the range of 0.15-1 meter.

Preparation can be made of concrete, bulk or film materials.

Types of training

Before starting the main work, it is necessary to carry out preparations. The work package includes the following three stages:

performing calculations;
leveling the site;
preparing the surface before laying the foundation.

First preparatory stage involves careful calculations and work with documentation. Then you need to clear the site. You will need to remove debris from the area, cut down and uproot trees, dig up bushes and other plants. The next step involves creating a “cushion” on the surface, which will be located under the foundation of the future building. The following building materials are used for this:

Preparation device (work stages)

First you need to clear the soil surface and make a pit. Proper preparation deepening involves carrying out a series of works that are aimed at bringing the soil to the desired state. In other words, the soil must withstand the heavy loads specified in the project. It is necessary that after the foundation is laid, the soil tightly grips the foundation from below. First, you should form a pit, clean its bottom with a bulldozer, and then thoroughly compact the base. In addition, during compaction of the pit, the soil should be moistened or dried. Most often, trenches are dug by hand. In addition, builders visualize the surface of the base itself and set the corners of the walls using pegs. After the pit is dug, specialists begin the following stages of construction:

marking the construction site for the foundation;
leveling the area;
Preparation required quantity crushed stones (layer - ten centimeters);
compacting the pillow using a vibration device;
installation of formwork (its height depends on the layer of concrete mixture layer;
pouring mortar to the top of the formwork;
reinforcement of the pillow (cross-section of the rods - at least eight millimeters);
compaction cement mixture vibrating plate;
installation of a reinforcement cage that allows you to fasten the crushed stone cushion to the base (they should protrude above the poured concrete by about twenty to thirty centimeters).

You can install a reinforced frame in concrete, but you can do without this material. In practice, the two options have almost no differences. The only difference is that a pillow created without reinforcement is limited in size. will strengthen the bottom of the cushion, which absorbs the pressure arising from the load of the structure and transmitted through the base.

Laying the foundation is one of the most important components of construction work. Not least important in this process is the construction of a special concrete footing, which should be located under a solid foundation. The quality of its execution determines the stability and durability of the structure. Before carrying out work, it is necessary to determine what density of concrete or crushed stone layer is needed for the construction of a particular building.

The footing is a layer of concrete mortar that must be prepared for the economical, convenient laying of the main foundation. This thin layer is poured to the main mass (for example, during the construction of the base using concrete slabs).

Purpose and thickness

The preparatory concrete or crushed stone foundation is made using different methods, means and building materials. But with any device, its purpose will remain the same - it consists in preparing and leveling the surface. Due to this, the main concrete pour is consumed more economically due to uniform placement, which does not require additional consumption of the mixture for unevenness and depressions in the ground. Concrete and crushed stone footing, which is required for construction work, is used in the following cases:

Surface preparation for easy installation of structural parts. On a leveled site it is much easier to do markings, reinforcement cages, etc. Obviously, this work is more difficult to carry out on loose soil.
Waterproofing. Thin concrete bases are also necessary in order to retain moisture from the poured mortar. Cracks appear on the frozen slab. They often appear due to the fact that the liquid is unevenly distributed in the cement structure.
Protection of the foundation from groundwater. If the layer is laid under a slab base, groundwater may enter the pit. In these cases, the footing absorbs part of the liquid, thereby preserving the load-bearing layer on which the building rests.

Preparation can be made of concrete, bulk or film materials.

Types of training

Before starting the main work, it is necessary to carry out preparations. The work package includes the following three stages:

performing calculations;
leveling the site;
preparing the surface before laying the foundation.

The first preparatory stage involves careful calculations and work with documentation. Then you need to clear the site. You will need to remove debris from the area, cut down and uproot trees, dig up bushes and other plants. The next step involves creating a “cushion” on the surface, which will be located under the foundation of the future building. The following building materials are used for this:

Preparation device (work stages)

First you need to clear the soil surface and make a pit. Proper preparation of the depression involves a number of works aimed at bringing the soil to the desired state. In other words, the soil must withstand the heavy loads specified in the project. It is necessary that after the foundation is laid, the soil tightly grips the foundation from below. First, you should form a pit, clean its bottom with a bulldozer, and then thoroughly compact the base. In addition, during compaction of the pit, the soil should be moistened or dried. Most often, trenches are dug by hand. In addition, builders visualize the surface of the base itself and set the corners of the walls using pegs. After the pit is dug, specialists begin the following stages of construction:

marking the construction site for the foundation;
leveling the area;
preparing the required amount of crushed stone (layer - ten centimeters);
compacting the pillow using a vibration device;
installation of formwork (its height depends on the layer of concrete mixture layer;
pouring mortar to the top of the formwork;
reinforcement of the pillow (cross-section of the rods - at least eight millimeters);
compacting the cement mixture with a vibrating plate;
installation of a reinforcement cage that allows you to fasten the crushed stone cushion to the base (they should protrude above the poured concrete by about twenty to thirty centimeters).

Many novice builders ask the question “concrete, what is it and why is it needed?” It is not difficult to understand what this structure is, since from the name it is clear that this is a thin layer of material with which the foundation pit is covered before laying the foundation (often such a layer is also called a pillow). However, it is worth deciding why you need to do this, and whether it is necessary to install concrete when building a house or bathhouse.

Why do you need to install a concrete footing?

Footing performs a whole series useful functions, namely:

Creates a layer of waterproofing. Thanks to this, the liquid cement mortar will not leak during the process of pouring the foundation. In addition, the moisture in the screed will be distributed evenly and the base will not crack when drying.
Allows you to create a rough concrete base flat surface. Thanks to this, the consumption cement-sand mortar decreases.
Protects the foundation from groundwater.
Redistributes the pressure exerted by the soil and ground parts of the structure.
Allows for higher quality reinforcement.
Eliminates shrinkage of the building.

In addition, such a shock-absorbing layer significantly improves the strength and durability of the entire structure. A foundation laid on a concrete base “survives” the winter more easily.

From all of the above, it becomes obvious why a footing is needed, so let’s move on to the varieties of these slabs.

Types of simple concrete footings

There are several types of foundation slab:

Shchebnevaya

This “preparation” is considered more economical, since crushed stone is cheaper cement composition. The crushed stone layer must be at least 20 cm high. In the process of laying the concrete footing, careful compaction (preferably using vibratory tamping equipment) is a prerequisite.

If it speaks of the shortcomings of “preparation,” then the technology for laying crushed stone footings under the foundation is considered unreliable. The fact is that such a substrate is not rigid enough, so further work installation of a foundation on such a foundation will not be carried out properly high level. However, if you don't plan to build multi-storey building, then such a concrete base will be quite sufficient for a utility block or bathhouse.

To install a simple base, follow these steps:

Prepare work surface and lay crushed stone on it.
Level it with shovels.
Compact and compact the pillow over the entire surface.
Apply a layer of bitumen to the resulting footing to obtain good waterproofing. If you want to save money, you can use roofing felt or polyethylene instead of bitumen, however, these materials have lower waterproofing properties.

Sandy

“Preparation” of sand allows for the best redistribution of loads on the foundation. It is recommended to lay such pillows in autumn and spring, when the soil undergoes changes. Due to the underlying layer of sand, the lower part of the foundation will be located above the groundwater level, so the monolith will not suffer from the harmful effects of moisture. That is why sand concrete footings are most often installed in areas with problematic soil.

To install such a layer you need:

Remove the layer of soil.
Fall asleep instead river sand fraction of at least 1.5 cm.
Using building level, level the pillow around the entire perimeter.
Compact the “preparation”.

Healthy! To determine required thickness footings, and also choose desired type layers, it is necessary to take into account: soil type, the presence of surrounding buildings, seismicity and operating loads. Detailed requirements and calculations are set out in SNiP 2.02.01-83, as well as in SP 50-101-2004 and SP 63.13330.2012.

Sand and crushed stone cushions are not suitable for all buildings and are characterized by low strength. If you want to make the most reliable foundation for a residential building, then, of course, you should give preference to a concrete slab.

Concrete pad

Construction of this type of concrete requires large financial investments, however, it is precisely this base that is best suited for slab and strip foundation. The fact is that when installing such fundamental foundations, a heavy reinforcing frame made of rigid steel rods is installed, which requires a more durable foundation.

Before you start installing the base, you need to consider a few tips:

To install the footing, “thin concrete” of classes from B 3.5 to B 7.5 (M 50, 75, 100) is used. There is no point in using stronger cement; besides, it will cost many times more.
To obtain a durable “preparation”, it is enough to lay a concrete pad 10 cm thick (provided that groundwater does not predominate in the area).
Before laying the concrete mixture, it is necessary to pour a thin layer of sand or crushed stone onto the bottom of the pit or trench.
If a reinforcing frame is not used when installing a concrete pad, then optimal thickness the base will be 15-20 cm.

Thanks to the reinforcement of the concrete base, the ground part of the structure will be located on a reliable foundation. For the armored belt, metal rods with a cross section of 8 mm are used. The rods are installed vertically and should protrude above the surface by approximately 25-30 cm. In this case, the thickness of the “preparation” can be reduced by 6-10 cm.

Installation of concrete footing

Let's say you plan to build a house on a site with fairly loose soil and a high groundwater level. To do this you need to complete the following steps:

Determine the highest point of groundwater - it is better to do “preparation” exactly to this level. Some install the “preparation” in such a way that it protrudes beyond the underground structure by 10 cm.
Level and compact the soil.
Pour coarse sand into the bottom of the pit, spread it over the surface and compact it thoroughly. For better effect, you can also lay a layer of crushed stone.
Lay roofing material or polyethylene on top of the sand.
Lay the reinforced frame with cells 60 x 60 cm.
Install guides; it will be more convenient to level the liquid mixture along them.

Mix cement, crushed stone, sand and water until a homogeneous thick mass is obtained.
Pour the concrete solution and level it along the beacons using the rule.
After the base has hardened, treat the surface with bitumen.

Healthy! In order not to use expensive drilling equipment after the monolith has hardened, it is recommended to think through openings for communications at the stage of laying raw concrete.

In conclusion

Depending on the type of construction, sand, crushed stone or concrete “preparation” can be laid. Such a cushion will give the entire structure additional strength and protect the foundation from groundwater.

In fact, it is very simple to understand what a footing is. Here even the name speaks for itself - this is a layer of thin concrete, which is prepared for comfortable and economical pouring of the main volume of the mixture. Essentially, this layer is placed under the main layer of concrete when installing slab foundations, For example.

But why exactly this needs to be done (and whether it is necessary at all) is worth understanding in detail. In addition, it will be useful to consider what the installation instructions for such a base are.

Let's start with the most important thing.

Purpose of the footing

It is worth noting that the preparatory layer can be made in different ways and different materials can be used. However, the meaning and purpose of this work remains the same ().

Purpose of the work	What does this give in practice?
Leveling the rough base.	This allows you to reduce the amount of the main mixture when pouring, that is, save a little. This happens due to the fact that the concrete layer will be laid down evenly and there will be no leakage of the solution into unknown holes.
Preparing the surface for easy installation various elements designs.	The convenience lies in the fact that on a flat area you can much faster make markings, assemble a frame from reinforcement and install beacons, for example. Agree that this is not so easy to do on loose soil with holes and bumps.
Creation of a waterproofing layer.	What this means is that, thanks to the presence of the concrete base, when pouring the bulk of the mixture with your own hands, moisture from the solution will not disappear anywhere. Accordingly, cracks will not appear on the finished slab or screed, which usually form due to uneven distribution of moisture within the structure of the working area.
Creation of protection against groundwater.	That is, if this layer is made under a slab-type foundation and groundwater often appears at the bottom of the pit, then in this case the footing is required to take the moisture “on itself” and prevent it from passing further into the main load-bearing layer of concrete.

In addition, the presence of such a shock-absorbing layer improves the strength characteristics of the entire structure as a whole. At a minimum, due to the fact that the base layer dries and gains strength better and of better quality.

Please note that the installation of concrete footings involves the use of inexpensive concrete mixture. As a rule, “skinny” concrete B3.5-B7.5 is used. That is, it turns out that thanks to the preparation of such a layer, the overall cost of the project is reduced, since a significant amount of the total cubic capacity is filled with a composition with a lower cost.

So, why this kind of work is needed is probably clear. Now let's figure out how this is all done.

Methods for constructing a footing

Before we begin, it is worth noting that concrete footing is, first of all, a very desirable measure, but not always mandatory ().

That is, simply put, if you have a small-scale project and the rough foundation consists of an old screed and there is no trace of loose soil or uneven terrain, then it is simply impractical to carry out such work.

So, objectively assess the situation - there is no need to waste your money where such extra work will not affect the final quality in any way.

Let's return to the options for constructing such a layer. As an illustrative example, let’s take the preparation for pouring a slab foundation.

Installation of the simplest concrete footing

For work we need this:

Crushed stone.
Tamping device. It is easiest to make from wood or metal.

Liquid bitumen.
Good and durable shovels.

We can begin.

The required amount of granite crushed stone is poured onto the working area. Typically, the material is dumped from a dump truck and the end result is a large pile of rubble.
Using shovels, the stones are evenly distributed over the entire surface.
A tamping device is taken and the crushed stone is compacted over the entire area.
A layer of bitumen is applied to the resulting surface.

Advice: you can save money and use not bitumen, but more or less durable roofing felt or even film. In any case, this will not provide particularly good waterproofing in the future, but at least these materials will allow the concrete to harden efficiently (without loss of moisture).

In general, the simplest version of the concrete footing has been implemented.

Now let's look at how to do this as correctly as possible.

Installation of capital footing

So, we have a working area with loose soil and the risk of groundwater.

We determine the highest point of groundwater - the footing will have to be made just up to this level (well, in any case, it is advisable to do it this way).
Using shovels, we try to level and level the soil.
We pour sand into the bottom of the pit and distribute it evenly over the surface, and then tamp it.
Lay a film or roofing material on top of the sand.
From thin reinforcement we make a kind of “cage” with a cell size of approximately 60 by 60 cm.

If desired, we install guide lines - beacons. It is convenient to stretch the mixture over them to get the most even surface in the end.
Mix cement, sand, crushed stone and water - you should get a homogeneous thick mass.
We pour the solution and, using the rule, distribute it over the entire area.
After the solution has dried, it needs to be treated with bitumen and, in fact, the construction of the footing is completed.

Advice: in almost every similar structure, holes for communications are then made. As a rule, this involves cutting reinforced concrete with diamond wheels using a grinder or simply drilling using a standard hammer drill. But you can make the work much easier and faster if you “lay” such holes in advance - in the still wet concrete.

But even if you simply simply forgot about such moments, and not only the lining layer, but also the main slab has already been poured, then you should not despair, because you can always use such a service as diamond drilling of holes in concrete with powerful industrial equipment.

In principle, that's all. The technology review is complete. Let's summarize.

Conclusion

We have figured out in detail what it is - concrete footing and how it is made. We also learned in which cases it is worth doing and in which it is not. We hope that all the information provided will be useful to you in practice ().

Well, if you want to know more, be sure to check it out. additional video in this article - there is a lot of interesting and useful information in this video!

Before building the foundation, in addition to preliminary calculations, you need to prepare construction site. The so-called concrete preparation for the foundation is needed first of all. It consists of erecting a pillow under the base.

Before building the foundation, in addition to preliminary calculations, you need to prepare the construction site. The so-called concrete preparation for the foundation is needed first of all. It consists of erecting a pillow under the base.

There are a number technical requirements regulating the technology of conducting preparatory work, the choice of material and the thickness of the layer used for the pillow. The list of basic standards and requirements for pre-foundation preparation is set out in SNiP 52-01, SP 52-101/2003 and SP 50-101/2004. They contain a lot of information on the topic that interests us. Basically, the role of fundamental preparation comes down to the following.

Main functions of the footing

If the foundation is planned to be poured locally, and not built from ready-made blocks, preparation for the foundation will help:

Protect the concrete mass from liquid leaks cement mortar. This will speed up the accumulation of the required volume by the foundation and the overall improvement of its quality indicators.
Level out force effects arising from soil pressure. Concrete preparation redistributes the forces arising in the soil and weakens them negative impact on the foundation.
Provide comfortable conditions for preparing the reinforcement frame of the base, which can be mounted on a flat surface.

Types of preliminary work

According to SNiP 52-01, for concrete preparation for the foundation, crushed stone, lean concrete (it has a low content of binders, and therefore a low grade - from M50) or profile membranes are used as the main material.

Crushed stone with bitumen

Crushed stone preparations are used to reduce the overall cost of the foundation and reduce cement consumption. The thickness of the crushed stone layer should be from 20 cm. After thorough compaction, the crushed stone is filled with bitumen. Crushed stone preparation is used in cases where it is necessary to fill the base of a pit with bitumen until the soil is maximally saturated or a bitumen film is formed.

The use of crushed stone preparation of the foundation cannot provide sufficient rigidity of the substrate. In addition, building a foundation on a crushed stone base is not entirely convenient. Therefore, it is used in the construction of auxiliary utility and technical buildings to minimize costs.

Concrete preparation

It is needed to ensure correct process construction of a concrete foundation and eliminating soil subsidence. Skinny concrete is not at all cheap option However, it is used quite often. Such concrete contains no more than 6% cement, the rest is crushed stone and gravel. The thickness of the concrete preparation layer should be 50 – 100 mm. It depends on the weight of the future building, the level groundwater and type of soil.

Concrete preparation for the foundation is used primarily in the construction of strip reinforced structures. This is due to the features technological process, which provides for the rigid installation of frames and steel mesh into the body of the future foundation before pouring it concrete mixture. In addition, it is much easier to build a foundation on concrete, especially in winter.

Profile membranes

A modern method of foundation preparation that can replace crushed stone and concrete preparation. When installing them, “wet” types of work are eliminated, money is saved, and the construction process is accelerated.

How to arrange concrete preparation

Work must be carried out in the following sequence:

First, you need to mark the construction site for the foundation.

The area needs to be leveled and covered with crushed stone in a layer of 10 cm.
Using a vibrating plate, compact the pillow.

Mark the perimeter and install formwork no more than 30 cm high. Its height will depend on the thickness of the concrete layer.
It is necessary to pour concrete mixture under the upper edge of the formwork.
With the help of reinforcement, the pillow is strengthened using rods with a cross-section of at least 8 cm.
Concrete must be compacted using a vibrating plate.
After filling the area with concrete mortar, you need to install reinforcement bars into it, the task of which is to fasten the foundation to the cushion. They should protrude above the concrete by about 20-30 cm.

On each side of the perimeter you must retreat beyond foundation slab by 10-15 cm, thereby increasing the size of the concrete preparation area. For a base made using the method concrete pouring there are no restrictions in use. It is considered so reliable that it is not necessary to reinforce it. In practice, both options have proven themselves with the most positive side. Their only difference is that the non-reinforced concrete pad has limited dimensions.

Construction requirements provide for a minimum height of the concrete layer, which must rise above the ground surface by no less than 15 cm. This allows for optimal placement of the reinforcement mesh. The mesh is needed to strengthen the lower part of the concrete pad, which experiences tensile forces. They are transmitted from the foundation, which experiences the weight load of the entire structure.

To understand why concrete preparation for the foundation is needed, you need to carefully study the existing regulatory documents. They say that any concrete preparation option is better than no concrete preparation. It will provide the building with the best strength and stability, helping the foundation long time maintain the entire structure in good condition.