Footing or sand cushion for the foundation. Why is concrete preparation necessary for the future foundation? Preparatory work for the construction of foundations

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 whole line 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 flat surface for a rough concrete base. 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 about 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 on installing the foundation on such a foundation will not be carried out at the highest level. However, if you do not plan to build a 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 a 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. This is why most often sand footings 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 a building level, level the cushion 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 solid 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 this kind of foundation that is best suited for slab and strip foundations. 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 concrete base, “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 the optimal thickness of 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 follow these steps:

Determine the highest point of groundwater - it is better to “preparation” 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.
Fill in concrete mortar and align it with 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 custody

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.

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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.

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 is poured to the main mass (for example, during the 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 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.

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.

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 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;
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 of the 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.

Why is SNiP necessary for concrete preparation for the foundation, and what requirements does it set for builders? What are these rules and regulations? These questions arise in the minds of many masters, both beginners and experienced ones.

In this article we will help you understand these issues and explain everything clearly.

Photo of preliminary foundation footing

Preparatory work for the construction of foundations

Preparing the foundation for a house should include the following steps:

carrying out preliminary calculations
foundation site preparation
preparation for the foundation.

Here we will focus on the last of the listed stages. In principle, the cushion under the base is made either from compacted crushed stone or from lean concrete and is easy to do with your own hands.

Technical requirements regulate the layer thickness building material which should have concrete preparation under the foundation also the technology of work. The basic standards and requirements for preparing the base are contained in SNiP 52-01, SP 50-101-2004 and SP 52-101-2003.

The main task of this stage of work is preparation for the actual construction of the foundation. Existing building regulations provide different kinds of these works, but the main one is the concrete footing.

Purpose of footings for monolithic structures

Protects the concrete mass from leakage cement mortar . This contributes to faster achievement of the required parameters of the base with an overall improvement in its quality
Eliminates the impact of forces from the ground. The footing distributes the forces that arise in the ground

Types of preliminary work

Crushed stone with bitumen

This is an unreliable method that has a serious drawback - insufficient rigidity of the substrate.

The result of this is the impossibility of ensuring maximum convenience for subsequent foundation work.

Naturally, for the construction of critical structures of this type should be avoided. However, for auxiliary, technical or ancillary buildings, its use is quite acceptable to reduce costs construction works.

Concrete preparation

The installation of concrete preparation for the foundation is becoming relevant for the construction of reinforced strip or slab structures. The main reason is that with such foundation construction technologies, it is assumed that steel meshes and frames are rigidly installed before pouring the concrete mixture.

An additional reason is due to the fact that on a hard surface the construction of a foundation is simplified in principle.

Important. This method acquires particular importance when carrying out construction work in winter, when the soil deteriorates its properties.

The main points contained in the instructions and rules:

The rules allow the use of concrete M50 and higher for concrete paving.
A total layer thickness of 10 cm is usually enough not only to level the site, but also to form a reliable foundation for the foundation being built.
A layer of concrete is laid on a bed of sand or crushed stone.

Installation of sand and crushed stone cushion

Sand preparation for the foundation ensures optimal redistribution of the load on the lower part of the foundation. The relevance of this is due to the fact that in spring and autumn the soil undergoes seasonal changes.

With the help of a sand cushion, the lower part of the foundation can be raised above the groundwater level and smooth out the deforming influences of foreign objects and materials due to the obstruction of direct contact.

Advice. It makes sense to install a sand cushion if there is problematic soil at the bottom of the pit.

In this case, the soil layer is removed and coarse river sand is poured in its place in a layer of at least 150 mm.

After this, it is leveled using simple levels and compacted with a special tool - a tamper.

Compacting a sand cushion

A high-quality sand cushion can be laid taking into account the groundwater level and its seasonal changes. At a high level, it may be necessary to construct a drainage layer (which, however, will not be superfluous in any case).

Layout of the sand cushion

To do this, a trench is dug along the perimeter of the structure being built, which protects against melt water and rising groundwater levels during heavy rainfall. This trench must be suitably waterproofed. Drainage will prevent flooding of basements.

Instead of sand, crushed stone preparation for the foundation can be used. It is stronger than its competitor. The material is crushed stone of fraction 20/40 mm. A small layer of coarse sand (10-15 cm) is poured under a 20-25 cm layer of crushed stone.

Crushed stone must be compacted using a vibrating plate. After compaction, the top layer of material should be at the zero level.

Pillow diagram using crushed stone

Important. The presence of a cushion determines the distance from the foundation surface to the reinforcement, which is called the protective layer.

When using a concrete pad, this layer can be halved from the standard 7 cm to 3.5 cm.

Foundation preparation device

Preparation from lean concrete
- Crushed stone preparation
- Profile membranes
Concrete preparation device for strip foundation
Installation of concrete preparation for a monolithic strip foundation
Preparation for prefabricated strip foundation
Installation of a pillow for a columnar foundation

How to prepare for foundation slab? Before starting work on the construction of the foundation, it is necessary to prepare the construction site. This is necessary to prevent cement leakage during pouring of the concrete foundation. Proper preparation of the construction site will provide a durable foundation for the house.

Scheme of laying a foundation made of lean concrete.

Preparation from lean concrete

The main goal of preparing concrete for construction site #8211 is to ensure the correct process of constructing a concrete foundation, to eliminate the possibility of soil subsidence, and to provide the building with the best stability and strength.

Using lean concrete #8211 is an expensive option, but nevertheless this method is the most traditional and often used. It is a cement mortar that contains no more than 6% cement. The filler is gravel or crushed stone. The solution is poured onto the bottom of the pit in a thin layer.

Scheme of a monolithic foundation with crushed stone preparation.

The thickness of the concrete preparation for the foundation depends on the level groundwater, type of soil, weight of the future building. It is recommended to use a layer thickness of 50 to 100 mm. Concreting eliminates the possibility of damage to the reinforcement frame and reinforcing mesh of the concrete foundation. If construction is carried out in winter, special anti-frost components must be added to the concrete. In winter, it is easier to make a concrete platform than a crushed stone platform, since the crushed stone still needs to be warmed up before starting work.

Under pile and monolithic structures, a gravel or crushed stone base up to 200 mm thick is installed. After compaction, gravel or crushed stone is filled with lean concrete. Its thickness must be at least 80 mm. When performing work on dense, dry soils, a cement layer thickness of up to 70 mm can be used.

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Crushed stone preparation

When carrying out construction work, the project indicates which type of concrete preparation should be used. The thickness of the crushed stone base is up to 200 mm. A concrete platform is constructed when it is used as a foundation. monolithic slab with reinforcement cages. A crushed stone base is used when it is necessary to fill the base of a pit with bitumen until a film forms or the soil is completely saturated.

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Profile membranes

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Concrete preparation device for strip foundation

Strip foundation diagram.

Lean concrete grade B 7.5 contains a small concentration of cement. It is used to create concrete preparation for various types of foundations. For other works in civil and civil construction industrial buildings Concrete grade M 15 is used. It is more difficult to prepare. The filler in this mixture is expanded clay.

For 1 m³ of solution for grade B 7.5, the following components are required: 160 kg of cement, 2200 kg of sand, 70 liters of water. For one bag of cement grade B 7.5 you need to take the following amount of materials: 25 kg of cement, 340 kg of sand, 10 liters of water. It is necessary to distribute a certain amount of sand over the site. Cement is then placed on top. After this, the cement and sand are mixed with a rake until a homogeneous mixture is obtained. Then pour evenly on top required amount water, level the mixture and compact it. The cement is then covered plastic film, in order to protect it from drying out.

Installation of concrete preparation for a monolithic strip foundation

Sequence of work:

They mark the future construction site for a monolithic strip foundation.
Level the soil on the site.
Pour crushed stone in a layer of 10 cm.
A vibrating plate is used to compact the future cushion under the strip foundation.
Install the formwork around the perimeter of the marking.
Install the formwork.
Concrete is poured to the level of the formwork.
The pillow is reinforced for strength using reinforcement. Reinforcement with a cross section of 8 mm is used.
When pouring, concrete is compacted with a vibrating plate.

Types of strip foundations.

First, a sand or crushed stone base is created by compacting the rock into the ground. Then the formwork for the foundation cushion is installed. The height of the pillow is 30 cm. The formwork is installed from boards. Two formwork boards with a width of 150 mm will allow you to pour a cushion 30 cm thick. Then the crushed stone base is filled with hot bitumen. After this, reinforcement is performed. Reinforcing mesh is fixed in accordance with the project. The lower mesh is installed at a height of 70 mm from the base. Then the pillow is concreted. After the concrete has hardened, the formwork is removed and the side surfaces are insulated with mastic.

The area on which the cement base is mounted may have dimensions exceeding the size of the foundation by 10 cm on each side. After pouring, it is recommended to install reinforcing bars vertically into the solution. They will connect the pillow to the foundation. The reinforcement should protrude 30 cm above the surface of the mixture. Currently, the most reliable is a cement base. It is recommended for all types of concrete foundations in the construction of buildings.

The concrete base for a monolithic strip foundation can be strengthened with reinforcement. Sometimes they do without fittings. In the construction of buildings, both of these bases are equivalent. The difference is that the airbag is limited in size. The minimum thickness of the concrete layer is about 15 cm. The reinforcing mesh is used as a reinforcing element. The mesh is placed at the bottom of the pit so that it is located at a distance of 5 cm from the ground.

In this case, the reinforcing mesh will be located the best way. It can be made from 8 mm reinforcement rods. They are tied together with wire. The mesh can also be made by welding. The reinforcing mesh strengthens the lower part of the concrete pad. The pillow is subject to tensile forces. They arise from the weight of the building itself and other loads.

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Preparation for prefabricated strip foundation

Foundation reinforcement diagram.

Installation of this design allows you to take long breaks from work. When installing a strip foundation, this is impossible. Under a prefabricated strip foundation they use concrete blocks factory-made or homemade.

For blocks made of aerated concrete and foam concrete, they arrange concrete base on the sand. In this case, the layer of sand is 10 cm. It is moistened and compacted. The formwork is installed on top at the level of the concrete layer. Then the cement mortar is poured. For building foundations, a concrete base is most preferable to compacted sand preparation.

Installation of a pillow for a columnar foundation

Concrete preparation: installation of floor screed and footings for the foundation

Concrete preparation is essentially a layer of lean concrete. which is installed under any structure made of a cement-sand mixture or of the same concrete.

Now about the technology in more detail.

In addition, the concrete preparation device according to ENIR makes it possible to carry out all roughing and marking work more economically, faster and with better quality before the main pouring. After all, you must admit that it is easier to install guide beacons for the same screed on a flat and solid plane than on loose, textured soil. And it’s easier to fill the screed itself in such conditions.

Please note that sub-concrete for floors is not made when the screed is poured onto floor slabs or other similar surfaces. In such cases, it turns out that the working plane is already quite solid and level.

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Footing or crushed stone for a strip foundation

If the reliability and durability of a building and structure depends on the quality of the foundation, then the quality factor of the foundation itself depends on competently carried out preparatory work. The choice of type of preparation depends on the characteristics of the building area and the materials of the underground part of the structure.

There is sand, gravel or concrete preparation. Like for the lungs frame houses, and heavy monolithic structures and houses made of stone, it is necessary to prepare the foundation for a strip foundation.

Concrete preparation is more expensive than crushed stone, but more practical. The thickness of the preparation from crushed stone is 20 cm, from lean concrete 10 cm.

Advantages of concrete preparation

A 10 cm layer of thin concrete will be able to level out all the unevenness that was made during the execution earthworks. The use of this technology makes it easy and convenient to install reinforcement cages in accordance with design provisions. Also, a base made of lean concrete will prevent metal contact with the ground, and, consequently, its corrosion.

The concrete footing makes it easier to mark axes, tie walls and other structures. In fact, this layer serves as additional waterproofing, which, during the construction of the foundation and hardening of the concrete, prevents the “cement laitance” from leaking into the ground. As a result, the actual grade of the material is not reduced, and the process uses the volume of building materials planned in the project. This technology can be used in almost any building area. Arrangement of the footing during the hardening of the foundation causes moisture retention, which makes the process as correct as possible.

A crushed stone cushion can be chosen if the soil at the bottom of the pit is thoroughly compacted and the groundwater level is below the level of preparatory work. But in this case it is better to equip additional waterproofing. You will also have to try with the reinforcement so that it takes a position adequate to the project.

The technology is regulated by three standards: SNiP2.02.01-83, SNiP13330.2012 and SNiP50-101-2004. These documents require design and calculations to be carried out in accordance with: the type of soil, the characteristics of the surrounding buildings, taking into account real loads, taking into account the seismicity class of the area and the environmental requirements of local authorities.

How concrete preparation is performed

We thoroughly compact the soil in the trench or pit and level it

It must be said right away that the footing is not a mandatory element of the structure. If your project is not large-scale, the soil on the site is dense, the terrain is flat, and the rough foundation requires a tight steel tie, it is not economical or practical to carry out the work, since additional efforts will not affect the result in any way.

Level the bottom of the trench with fine crushed stone and compact it

If concrete preparation is advisable, then its arrangement should begin with digging a trench and compacting its bottom. Its depth is the sum of the thickness of the cushion and the thickness of the footing. The calculated amount of sand and stone is poured onto the bottom of the trench, which are also compacted. Next you need a layer of waterproofing. It can be bitumen, roofing felt or film. The concrete preparation for the monolithic strip should extend beyond the underground structures by 10 or 15 cm. Taking these values into account, the sand-crushed stone cushion should also be formed.

We pour M100 grade concrete into the formwork and level it

It is important to water the concrete in the first days of setting with water using a sprayer (not a stream). After two or three days, the formwork is removed and waterproofing can be applied and the reinforcement frame placed under the strip foundation.

When pouring concrete, do not forget to water it with water, otherwise the concrete will not ripen, but will dry out.

Formation of formwork and reinforcement cage

In order for the foundation to work in the form of an “inverted T”, reinforcement is necessary. At this stage it is necessary to set up the formwork. For concrete preparation, it is enough to use 150x40 boards, which are secured with stakes in a horizontal position. Then reinforcement is laid out at the bottom of the created structure, according to the design. Upon completion of the work, mixing of the lean cement mortar begins, where the content of the cement itself is not high. Crushed stone and sand are used as fillers. The finished material is poured into the formwork. It also needs to be compacted to expel the air using a vibrator.

Upper layer the concrete footings must be leveled and covered with a film that will prevent the surface from drying out intensively. Depending on the density of the soil, the thickness of the concrete preparation can vary from 6 to 10 cm. Construction regulations recommend not allowing the structure to slope more than 5 mm per 1 meter of strip foundation length. If you want to achieve a reliable connection between the footing and the foundation, it is advisable to install vertical metal rods so that they rise above the surface from 20 to 30 cm.

Almost every construction project involves passage through such communications structures. They can be made at the next stage of construction of the object using a grinder or drilling. But it is more rational to “fill” such holes during the construction of concrete preparation - in the raw mortar. This will save time and money.

The main functionality of concrete preparation:

protection against leakage of concrete mortar, which accelerates the achievement of the necessary characteristics of the base;
forces arising in the ground are redistributed through the footing, it neutralizes their effect;
optimization of the reinforcement process;
concrete preparation allows construction work to be carried out in winter time of the year;
the leveled surface simplifies the work and makes it more accurate.

To mix a lean solution, you can use concrete up to grade M50. Mostly this technology used for the construction of strip and slab foundations. The exact width and thickness of the footing must be calculated in accordance with the expected deformations and bearing capacity.

It is not always necessary to choose concrete as a base for the foundation. But this technology makes it possible to construct reliable and durable foundations even in problem areas of development. The work should be guided by building regulations. So, as a result, you will get a house that will delight you and your descendants.

Why is concrete preparation necessary for the future foundation?

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 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 leakage of liquid 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 their 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 by no means a 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, groundwater level and type of soil.

Concrete preparation for the foundation is used primarily in the construction of slab and 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 it is poured with 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, it is necessary to retreat beyond the foundation slab by 10-15 cm, thereby increasing the size of the concrete preparation area. For a base made by pouring concrete, there are no restrictions on its 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 regulations. 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.

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When carrying out construction, it is important to correctly carry out preliminary calculations, as well as technically competent, high-quality preparation of the foundation, which determines the stability of the building’s foundation. Concrete preparation for the foundation is a complex of works for the construction of a cushion under a future facility.

Choice optimal option The implementation of preparatory measures affects the reliability of the foundation and the service life of the construction project. A properly prepared base, proportional to the area, redistributes the loads acting on the ground and prevents leakage of the cement mass, which is possible during the process of pouring concrete mortar.

Forming a pillow is a responsible operation. That is why the technical requirements that determine the features of preparatory activities, technology, required material, the thickness of the layer used for the pillow is regulated by SNiP and a set of rules, the recommendations of which we will consider further in more detail.

There are a number of technical requirements regulating the technology of preparatory work, the choice of material and the thickness of the layer used for the pillow

What regulatory documents and rules must the installation of concrete preparation for the foundation meet?

When carrying out industrial and civil construction, the construction of any types of structures is subject to special provisions given in industry and state standards, building codes and codes of practice. The main documentation regulating the specifics of the work is:

SNiP 52–01, issued in 2003, deals with structures made of concrete and reinforced concrete;
SP 50–101, approved in 2004, containing requirements for the design and construction of foundation foundations;
SP 52–101 (2003), devoted to structures without prestressed reinforcement;
SNiP 2.02.01, developed in 1983, regulating the parameters of the foundations of construction projects;
SP 63.13330.2012 is a set of rules that combines requirements for building structures.

These standards clearly define the features of activities related to the construction of foundations and their design. They take into account:

Soil characteristics at the construction site.
Specifics of the development object.
Environmental requirements.
Actionable efforts.
Degree of seismic activity.

The requirements of regulatory documents are subject to strict compliance construction companies and organizations carrying out design work.

The construction of any structures during the construction of civil and industrial facilities is subject to certain requirements

The requirements of building codes and codes of practice stipulate that in order to form a foundation it is necessary to perform one of the specified types of preparation. We list the possible options:

the base is made of lean concrete, characterized by a low grade and a low percentage of binding ingredients;
crushed stone preparation for the base, 200 mm thick, providing a significant reduction in cement consumption. The crushed stone is compacted and filled with bitumen solution;
profile membrane base, combining the features of the above types of work.

Increased strength is provided by the first option, after which it is more convenient to carry out further work on arranging the foundation. Let's look at it in detail.

The installation of concrete preparation for the foundation ensures the required state of the foundation, which has the necessary load-bearing capacity sufficient to withstand the applied forces. That is why building codes pay increased attention to it. What is the main purpose of the concrete base, which is the basis of monolithic structures? What tasks does it perform?

Concrete preparation for the foundation is used primarily in the construction of slab and strip reinforced structures

Ensuring the protection of the poured solution from leakage, which contributes to the rapid hardening of the base in accordance with the requirements of the technology, improving its quality. Lack of moisture causes cracking of the massif, reducing the strength of the base and its subsequent destruction over time.
Creation of a flat surface that allows a geometrically correct, stable installation of the base frame and reinforcement in accordance with the requirements of SNiP.
Leveling the reaction of the soil on the base of the sole, uniform distribution of force over the entire area.
Preventing possible soil shrinkage under the influence of point forces and significant loads.

The preparatory stage, according to the rules, involves the following steps:

the calculation part, which determines the thickness and dimensions of the foundation base, its ability to withstand deformations;
arrangement of the work area;
formation of the site.

According to SNiP 52-01, crushed stone is used as the main material for concrete preparation for the foundation

Building regulations require calculation of the forces that the base can absorb in the following cases:

In the presence of severe compressive forces.
When the construction site is located near embankments, slopes or slopes.
When arranging the base of the foundation located on weak soils.

The standards allow not to carry out calculations of bearing loads if, according to the project, measures will be taken that do not allow soil movement.

As forces acting on the base, the set of rules takes into account all transmitted loads, acting both short-term and throughout the entire period of operation. The mass of the part of the object below the zero mark is also taken into account.

The main stages of work to prepare the soil for installing a concrete foundation include:

arrangement and marking of the pit, taking into account the future thickness of the layer sand and gravel mixture and concrete;
planning and cleaning the bottom of the excavation;
compaction of loose soil using vibrating plates;

Regardless of the type of soil, at the first stage of work on preparing lean concrete for the foundation, the bottom of the excavation should be leveled

additional moistening or drying of the soil, depending on the results of compaction work;
adding sand-crushed stone fraction 10 cm thick, necessary for drainage;
compaction of the massif;
applying a waterproofing layer of film or roofing material sheets;
assembly of formwork with a height of no more than 30 cm for concreting.

Only after this they begin concreting work. These are the main stages provided for by the standards that make up the concrete preparation for the foundation.

According to building codes, concrete preparation for the foundation requires strengthening the concrete mass with steel reinforcement. This measure improves the reliability of the part of the building located below the zero level and strengthens the footing.

The base is reinforced with steel mesh connected with special wire with a diameter of 8 millimeters. The structure is laid on the base before the formwork is filled with the mixture. The standards provide for the installation of vertically located steel rods that ensure a strong connection between the foundation and the base. Steel rods must rise above the surface of the base by at least 20 centimeters.

Reinforcement significantly strengthens the concrete base and increases the reliability of the underground part of the structure

The main provisions contained in building codes and codes of practice related to the implementation of a cushion based on lean concrete:

It is allowed to use a solution of grade M50 and higher. To perform the work, lean concrete is used, which is a type of cement mortar that contains no more than 6% class B15 cement. Sand and gravel play the role of filler.
The poured mass for foundation slabs or a monolithic base must extend beyond the level of the underground part of the structure and rise above it by 100-150 mm, which is ensured by the design of the formwork prepared in advance.
The solution is poured onto a pre-made crushed stone-sand base.
Air bubbles are removed by compacting the mixture.
Protection against surface dehydration is provided by polyethylene film, which is used to cover the poured surface in the first days.

Is it possible to make a footing without reinforcement? What is the recommended thickness of the concrete footing made without reinforcement by building codes? Building rules allow this option, for which the thickness of the concrete layer is 150-200 mm.

When arranging a reinforced base for a foundation, the set of rules allows for a reduced base height. The layer thickness in this case is 60-100 mm. The size is influenced by the mass of the structure, the level of groundwater, and the type of soil.

Construction requirements provide for a minimum height of the concrete layer, which must rise above the ground surface by no less than 15 cm

According to SNiP, the tolerance for surface flatness when forming a monolithic strip does not exceed 0.5 cm for each meter of length and no more than 5 centimeters for solid slabs with a width of over 25 meters.

Concrete preparation for the foundation is especially important if construction activities are carried out in winter, since a flat surface facilitates the further implementation of the foundation work envisaged by the project.

The use of prepared foundations based on crushed stone allows you to reduce the costs of construction activities. After all, cement is saved, and the cost of purchasing crushed stone is quite acceptable. Crushed stone preparation for the foundation is permitted by the set of rules and building codes. In this case, the layer thickness should be about 20 centimeters. The crushed stone layer must be thoroughly compacted and filled with liquid bitumen. Filling the bitumen solution is carried out if it is necessary to saturate the soil as much as possible or to form a waterproofing bitumen film. This method does not provide high rigidity of the substrate and makes it difficult to carry out foundation measures. It is widely used for low-responsibility construction projects technical purposes, utility rooms and auxiliary buildings.

Collections of building codes and regulations when preparing foundations provide for the use of modern technological solutions, which include profile-type membranes. Their use simplifies the process of forming the base, since types of work associated with concreting are eliminated. The absence of “wet” stages of work saves resources and simplifies the process of installing the base. The result is a reduction in preparation time.

By carefully studying the collections of current building codes and codes of practice, builders and designers will gain a complete understanding of the requirements for foundation preparation activities. After completing the preparatory work in compliance with the recommendations of regulatory documents, the construction project will be durable, increased stability and will be able to be used for a long time. After all, a concrete pad is the optimal solution for ensuring the reliability of a structure!

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Soils have a heterogeneous structure. Under heavy loads they can shrink, sag and collapse. In order to evenly distribute the pressure from the building, reduce the settlement of the house and prevent further shrinkage deformations, various types of preparations are arranged under the foundations - sand, crushed stone, gravel or concrete.

In weak soils - peat bogs, sapropels, waterlogged clays or silty soils - this is not enough. In this case, the base is erected using concrete preparation for the foundation.

Why do you need a footing, in what cases is it made of concrete, and when can you get by with a cheaper option - sand or crushed stone preparation?

Functions of the footing

Concrete preparation for the foundation is a layer of lean concrete between crushed stone or gravel backfill and the material of the main structure. Its thickness is within 10 cm.

The main function of the footing is to provide reliable support for the foundation of the building:

on weak soils;
near slopes, embankments and slopes;
at high compressive load from the structure;
in earthquake-prone regions.

In these cases, the dimensions of the footing are calculated according to the standards - SNiP 2.02.01-83, Construction Rules 50.101.2004, 63.13330.2012. They indicate the basic principles for selecting the composition of concrete, installing a preparatory layer, installing a reinforcement cage, and performing work.

Additional functions of concrete preparation are:

ease of installation of prefabricated structures on a leveled surface;
precise installation of reinforcement cages when constructing a monolith, since it is much more difficult to align them horizontally on a bed of crushed stone;
in creating an additional protective layer from soil moisture that destroys the main structures;
in the cost-effectiveness of using high-grade concrete when laying it on a leveled, dense base made of inexpensive material;
By preventing the flow of cement laitance from the freshly poured mortar of the main foundation structure, the hydration of the binder grains is complete, and the grade of concrete is not lost.

It is advisable to arrange concrete preparation for massive and large-scale structures. Light frame or small buildings on flat terrain and dense soils are erected on a compacted base - sand and crushed stone bedding. Its purpose is protection against freezing, removal of soil moisture, and prevention of soil heaving.

Types of preparation

The most common types of preparation:

sandy;
gravel or crushed stone;
concrete;
membrane

Sand and crushed stone preparation

At the first stage, after excavation work, backfill is made from inert materials, followed by compaction with tampers. The thickness of the sand, crushed stone or gravel cushion is 20-60 cm. If the groundwater level is high, geotextiles are spread along the bottom of the pit.

Large fractions are laid first, then medium ones. They provide drainage to the base. The top layer is covered with sand. This distribution of materials by size gives the cushion under a strip or slab foundation greater rigidity and strength. The use of sand in preparation is necessary for uniform transfer of vertical load to the underlying layers.

The requirements for fine aggregate are:

use sand with a grain size of 2-2.5 mm, the most suitable for filling pillows - crushed gravel with low specific gravity and high water throughput;
the amount of clay particles, lime and salt contaminants should be minimal;
organic residues lead to a rapid loss of water permeability and siltation of the sand layer, so their presence is not allowed.

The backfill for the foundation is made of gravel, granite or crushed limestone with an average strength of M800 and a fraction size of 20-70 mm. Layer-by-layer compaction with a vibrating plate or manual tampers is mandatory every 50 mm. The sand is first spilled with water.

Concrete preparation

The cushion under the slab or foundation blocks is made in two ways. The first is pouring a layer of crushed stone with liquid bitumen, the second is constructing a footing made of low-grade concrete M50-M100 with a layer of up to 10 cm.

A concrete pad for the foundation is made:

pouring into a trench or the bottom of a pit without formwork;
installation of formwork around the perimeter of the site and subsequent spreading of the concrete base;
First, thin concrete is placed in the foundation form, then concrete of the design grade.

The solution is leveled using beacons or a rule, and compacted with a vibrator. The top of the concrete base is waterproofed with bitumen, rolled materials, and waterproof films.

Preparation with geomembrane

Polymer membranes have recently appeared on the construction market. Fiber is used to protect the foundation of a building from soil moisture, i.e. as waterproofing. What is fundamentally new is that the profile in the form of spikes simultaneously serves to strengthen the soil. Manufacturers claim that the use of geomembranes reduces the number of shrinkage cracks and redistributes forces when transferring load to the base. The cross-sectional shape prevents water from entering, and the voids between the insulation and the concrete are ventilated.

The fiber is laid using sand and crushed stone preparation; a layer of geotextile is first laid out. Membrane seams are connected by welding. The material is strong and durable, withstands high and low temperatures.

Sequence of work

Work on installing a footing for a foundation made of lean concrete is carried out according to the following scheme:

Level the bottom of the pit or trench.
Large and medium crushed stone is poured, leveled, and compacted. Layer height - 10-15 cm.
The next step is backfilling the foundation with sand of fraction 2-2.5 mm, moistening, tamping.
Install the formwork under the cushion under the strip foundation.
Reinforcement mesh and vertical outlets are installed to connect the foundation with the preparation of the base.
To fill the cushion, use M100 concrete with Portland cement grade no lower than M50. Layer height - 10 cm.
The surface is leveled and tamped with vibrators to release air from the thickness of the solution.
After 3-7 days, the formwork panels are removed.

Before installing the foundation, you need to waterproof the pillow using coating or rolled protective materials. According to SNiP permissible deviations horizontally should not exceed 5 mm when checking with a two-meter level, and along the entire length of the section - 20 mm.

Conclusion

Preparation for the foundation is an integral part of general construction work. Construction regulations prescribe in which cases it is necessary to determine the thickness, width, and reinforcement of a concrete pad under the foundation using calculations. For soft soils, high loads, difficult terrain, and in seismic zones, this is a must. In all other cases, the concrete footing is made as standard and has a thickness of no more than 10 cm.

A strong, reliable foundation is important for a house. However, for it, one should initially prepare a high-quality foundation on which it will rest, and open ground not suitable for this at all.

Compacted sand and gravel pads are often used, but they are not without disadvantages associated with high drainage and uneven load distribution. The foundation footing will help solve the problem and prepare the foundation, which will be discussed in this material.

The foundation of a house is often a monolithic reinforced concrete structure belt type or plate. Strength directly depends on the quality of the reinforcement, strict geometry of the reinforcement frame and quality of concrete.

All three parameters directly depend on the quality of preparation of the base on which the foundation will be formed.

A cushion of sand or gravel is a mandatory element of the base for laying the foundation. However, sand and gravel themselves, even when compacted, can negatively affect the quality of the concrete being poured.

You may encounter the following problems:

On a sandy or gravel bed it is difficult to mark with high accuracy angles and all necessary dimensions;
The reinforcement cage rests on supports, bosses or buried reinforcing bars, but they can be pulled down due to the heavy weight of the structure. Even with careful compaction, a point load will displace some of the sand or gravel;
When pouring high-grade concrete over the formwork, part of the cement laitance and mortar will go into the sand, thereby reducing the strength and grade of concrete, this is especially true when using deep-seated hand vibrators.

The foundation footing helps to get rid of the listed disadvantages of the sand cushion. The entire base area is simply filled with thin concrete up to 10 cm thick.

Due to its high fluidity and plasticity, concrete is easily leveled in one plane. For the footing it is not important that part of the solution goes into the prepared sand cushion.

The main thing is that a relatively flat plane will remain on the surface, much stronger than compacted sand.

The foundation footing is:

a solid basis for installation and preparation of the reinforcing frame;
protection of the base from deformation during all preparatory work;
a surface laid out in one plane on which it is convenient to mark the corners of the foundation;
the location of the walls of the future house and the correspondingly verified installation of reinforcing frame reinforcements.

In addition to this, the footing is an ideal surface for arranging a waterproofing layer, on which the main foundation will be poured.

The waterproofing layer will ultimately be protected on both sides by concrete and will not be subject to deformation, negative impact cold heaving of soils and even temperature changes along the foundation plane.

SNiP

To the construction of concrete monolithic foundations Strict requirements for the device and quality of the result apply. Main regulatory documents – these are SNiP 52-01 and SP 50-101-2004. To be negotiated general rules on preparing the base, laying the reinforcing frame, selecting concrete and pouring it.

The final document to refer to is finished project house, which indicates all the nuances and requirements for the construction of the house and the foundation in particular.

All work is carried out in strict accordance with the construction project, from the schedule to the requirements for marking, preparation of the base and foundation concrete.

The key information for pouring lean concrete is the brand of solution, the thickness of the required layer and, accordingly, the volume of material that should be ordered to the construction site.

It is advisable to take ready-made concrete from production and deliver it using a concrete mixer. For small volumes and small foundations, manual preparation of concrete mortar is allowed. It is important to maintain, first of all, the uniformity and uniform quality of the solution.

Concrete grade

For the foundation footing, lean concrete is used in accordance with the requirements of GOST 25192-2012, GOST 7473-2010. To prepare such concrete it is used minimal amount binder, cement and more aggregate, often coarse and medium gravel.

The surface of the mortar after pouring turns out to be non-uniform due to the protrusion of the filler; the cement mortar does not cover the gravel and only adheres the stones to each other.

The concrete class or grade is usually used. In accordance with the GOST classification, lean concrete class must correspond to B7.5 or lower and grade M50(75).

These indicators indicate the strength of concrete in a hardened state and are not related to the density of the material. So the higher the class or grade, the stronger the concrete and the more it can withstand loads.

There is no need to use durable or heavy-duty concrete. Lean concrete is enough, because its task is only to bind the base, to provide a flat and relatively strong platform on which you can adequately work and carry out preparatory work on the construction of the foundation, without fear of disturbing the already established plane.

Device

The first step is to prepare the site for building a house. Part of the soil with green spaces is removed and compared to the pit level. Next, trenches are prepared for the strip foundation or a pit is deepened over the entire area for a monolithic slab.

Depending on the type of soil and its properties, a sand or gravel cushion is formed. The thickness of the cushion is determined by the construction project based on the load capacity and characteristics of the base.

It is incorrect to compare the footing with a specific layer of sand or gravel; all three materials are involved in forming the base for the foundation.

Compaction of sand and gravel is carried out layer by layer 40-50 mm each. The sand must be moistened.

There are three options:

The footing is carried out without formwork along the bottom of a pit or trench;
Before pouring lean concrete, formwork is installed to cover a larger area;
Before pouring the base, formwork for the foundation is installed, along the bottom of which thin concrete is poured.

Pouring is carried out according to the general rules of concreting. The solution is prepared on site or delivered ready-made and distributed over the entire surface.

Using the rule and pre-installed beacons, the surface is leveled. Using hand-held immersion vibrators, the solution is compacted to remove air and ensure tight contact with the base.

Waterproofing

Waterproofing of the concrete base along the lower border is not carried out, except in cases specified in the construction project. Layer waterproofing material spread or applied over lean concrete after it has dried and before laying the reinforcing frame.

Concrete in the base will slow down the capillary suction of moisture under the foundation and will protect the waterproofing layer from cold heaving or any other deformation of the base soil.

The following can serve as waterproofing:

bitumen, which is applied in a layer of at least 2 mm over the entire surface of the base;
roofing felt and other rolled bitumen-containing materials;
geomembrane or dense polyethylene.

Rolled materials do not require additional fastening, but it is important to prevent damage to the waterproofing layer before pouring concrete under the foundation. Strips of waterproofing material are laid with an overlap of at least 15 cm.

The result will be a strong and reliable foundation for installing a reinforcing frame and subsequent pouring of concrete.

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 a hard and even preparation layer makes foundation construction easier in winter.

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, based on 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, which prevents 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 pouring the solution. 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.