Concrete preparation for foundation slab. What is the foundation for the foundation and what is it for?

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

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

Purpose and thickness

Preparatory concrete or crushed stone is made using different methods, tools and building materials. But with any device its purpose will remain unchanged - it consists in the preparation and leveling of the surface. Due to this, the main concrete pouring is consumed more economically due to a uniform laying, which does not require additional mixture costs for irregularities and depressions in the ground. Concrete and crushed stone, which is required for construction works, is used in the following cases:

1. Surface preparation for easy assembly of structural parts. On a leveled platform, it is much easier to make markings, reinforcement frames, etc. Obviously, on loose soil these jobs are more difficult to carry out.
2. Waterproofing. Thin concrete bases are necessary and in order to keep moisture from the poured solution. Cracks appear on the frozen plate. Often they appear due to the fact that the fluid is unevenly distributed in the cement structure.
3. Protection of the foundation from groundwater. If the layer is laid under the slab foundation, groundwater may enter the foundation pit. In these cases, the concrete absorbs a part of the liquid, thereby maintaining the carrier layer on which the building rests.

In addition, the presence of cushioning allows to increase 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 severity of the structure. On average, this indicator is in the range of 0.15-1 meter.

Types of training

Before the start of the basic work, it is necessary to prepare. The following three stages relate to the work package:

• execution of calculations;
• leveling of the site;
• preparation of the surface before laying the foundation.

The first preparatory stage involves careful calculations and work with documentation. Then you need to clear the pad. From the territory you will need to remove rubbish, cut down and uproot trees, dig up bushes and other plants. The next step is to create 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)

To begin with, it is necessary to clear the surface of the ground and make a pit. Competent preparation of the deepening involves a number 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 completion of the laying of the foundation, the soil should be tightly wrapped around the foundation from below. First it is necessary to form a pit, clean its bottom with a bulldozer, and then carefully compact the base. In addition, during the compaction of the foundation pit, it is necessary to moisten or drain the soil. Most often trenches are dig manually. In addition, builders sight the surface of the base itself, expose the corners of the walls using pegs. After the excavation is dug, the specialists begin the following stages of construction:

• marking the construction site for the foundation;
• alignment of the site;
• preparation of the required amount of crushed stone (layer - ten centimeters);
• tamping the cushion with vibration assist;
• installation of the formwork (its height depends on the layer of the concrete mixture of the layer;
• pouring mortar to the top of the formwork;
• reinforcement of the cushion (cross section of rods - a minimum of eight millimeters);
• tamping the cement mix with a plate compactor;
• installation of reinforcing cage, which allows to fasten the cushion of rubble to the base (they should protrude over the poured concrete by about twenty to thirty centimeters).

In concrete, you can install a reinforced frame, but you can do without this material. In practice, the two options have almost no difference. The only difference is that the pillow, created without reinforcement, is limited in size.

In fact, it's very easy to understand what the footsteps are. Here, even the name speaks for itself - it is a layer of fine concrete, which is prepared for a comfortable and economical filling of the main volume of the mixture. In fact, this layer is placed under the main layer of concrete when installing slab foundation, for example.

But here is why this should be done (and whether it is necessary in general) to understand in detail. In addition, it will be useful to consider what the instruction for mounting such a framework is.

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 the materials can be used different. However, the meaning, purpose of this work remains the same ().

In addition, the presence of such an amortization layer improves the strength characteristics of the entire structure as a whole. At least due to the fact that the base layer dries and recovers strength, better quality.

Pay attention to the fact that the device of the concrete means the use of inexpensive concrete mixture. As a rule, "lean" concrete В3,5-В7,5 is used. That is, it turns out that due to the preparation of this layer the overall price of the project is reduced, since a significant amount of the total cubic capacity is filled with a composition with a lower cost.

So, for what such work is necessary, probably, it is clear. Now let's see how this is done.

Methods of the device for concrete

Before we start, it is worth noting that the footing is, above all, a very desirable measure, but not always mandatory ().

That is, simply speaking, if you have a non-scale project and the draft base consists of an old screed and no loose soil or uneven terrain, and there is no trace, it is simply not advisable to perform such work.

So objectively assess the situation - do not waste your time there, where such additional work will not affect the final quality in any way.

Let's return to the options for the device of this layer. As an illustrative example, let's take the preparation for pouring a slab foundation.

Installation of the simplest concrete

For work we need this:

1. Crushed stone.
2. Trimming device.  It's easiest to make of wood or metal.

1. Liquid bitumen.
2. Good and strong shovels.

You can start.

1. The necessary amount of granite rubble is poured onto the work area. As a rule, the material is poured off the dump truck and, as a result, a large pile of rubble is obtained.
2. With the help of shovels, the stones are evenly distributed over the entire surface.
3. Take the tamping device and the crushed stone is compacted over the entire area.
4. On the resulting plane, a layer of bitumen is applied.

Tip: you can save and apply not bitumen, but a more or less solid ruberoid or even a film. Especially good waterproofing in the future this in any case will not give, but at least these materials will allow to qualitatively congeal to concrete (without loss of moisture).

In general, the simplest version of the footing is implemented.

Now consider how to do this as correctly as possible.

The device of the capital base

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

1. We determine the highest point of groundwater - the sub-concrete will have to be done just before this level (well, in any case, it is desirable to do so).
2. With the help of shovels we try to level, plan the soil.
3. We fall asleep on the bottom of the excavation sand and evenly distribute it on the surface, and then we ram.
4. We sew a film or roofing material on top of sand.
5. From thin armature we make a kind of "cage" with a cell size of about 60 by 60 cm.

1. If desired, we set guide lines - beacons. On them it is convenient to stretch the mixture to get the most flat surface as a result.
2. We mix cement, sand, crushed stone and water - a homogeneous, thick mass must be obtained.
3. Fill the solution and use the rule to distribute it throughout the area.
4. After the solution has dried, it needs to be treated with bitumen and, in fact, this completes the device.

Tip: in almost every such structure, then holes are made for communication. As a rule, for this purpose, cutting of reinforced concrete with diamond circles by a Bulgarian or simply drilling with a standard perforator is used. But you can greatly facilitate and speed up the work if you "lay" such holes in advance - in still raw concrete.

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

In principle, that's all. Technology review is over. Let's sum up.

Conclusion

We have in detail figured out what this is - the footing and how it is done. Also, we got acquainted with the cases in which it is worth doing, and in which it is not. We hope that all the information provided to you will be useful in practice ().

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

Many beginning builders are asking the question "what is it and what is it for?". It is not difficult to understand what this design is, since it is clear from the title that this is a thin layer of material that is covered with a pit before laying the fundamental foundation (often such a layer is also called a pillow). However, it is necessary to decide what for it is necessary to do it, and whether the execution of the concrete is mandatory for the construction of a house or a bath.

For what it is necessary to mount the concrete

The footing performs a number of useful functions, namely:

• Creates a layer of waterproofing. Due to this, in the process of foundation pouring, the liquid cement slurry will not flow. In addition, the moisture in the screed will be distributed evenly and the substrate will not crack when dry.
• It allows to create an even surface for a rough concrete foundation. Due to this, the consumption of cement-sand mortar decreases.
• Protects the foundation from groundwater.
• Redistributes the pressure exerted by the soil and the ground parts of the structure.
• It allows to produce better reinforcement.
• Eliminates the shrinkage of the structure.

In addition, such a cushioning layer significantly improves the strength and durability of the entire structure. The foundation laid on the base, it is easier to "survive" the winter.

From all of the above, it becomes obvious what is needed for the concrete, so let's proceed to the varieties of these plates.

Types of simple substrates

Plate for the foundation is of several types:

Crushed stone

This "preparation" is considered more economical, since rubble costs less than cement. The gravel stratum should be at least 20 cm high. In the process of laying the footing, a compelling condition is the careful ramming (preferably with the use of vibrating tampers).

If it talks about the shortcomings of "preparation", then the technology of laying the rubble substructure under the foundation is considered not reliable. The fact is that such a substrate is not rigid enough, so further work on the installation of the foundation on this basis will not be performed at the highest level. However, if you do not plan to build a multi-storey house, then such a footing will be quite enough for a business block or a bath.

Follow these steps to install the simplest base:

1. Prepare a working surface and lay on it rubble.
2. Align it with shovels.
3. Tighten and compact the pillow over the entire surface.
4. On the resulting concrete, apply a layer of bitumen to obtain a good waterproofing. If you want to save, then instead of bitumen, you can use ruberoid or polyethylene, but these materials have lower waterproofing performance.

Sandy

"Preparation" of sand allows you to best redistribute the load on a fundamental foundation. These cushions are recommended to be laid 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 that the monolith will not suffer from the harmful effects of moisture. That is why most often sandy substrates are mounted on sites with a problem ground.

To mount such an interlayer, it is necessary:

1. Remove the soil layer.
2. Fall asleep instead of river sand with a fraction of not less than 1.5 cm.
3. Using the building level, level the pillow around the perimeter.
4. To use "training".

Useful! To determine the required thickness of the substrate, and also to choose the type of interlayer required, it is necessary to take into account: soil type, 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 gravel cushions are not suitable for all buildings and are not very strong. If you want to make the most reliable basis for an apartment house, then, of course, it is worth giving preference to a concrete slab.

Concrete pillow

The construction of this type of concrete requires a lot of financial investment, but this is the basis that is best suited for a slab and a basement. The fact is that when mounting such fundamental foundations a heavy reinforcing frame made of rigid steel rods is installed, which requires a more solid base.

Before starting the installation of the base, it is necessary to take into account a few tips:

• For the installation of the concrete, "lean concrete" of classes from B 3.5 to B 7.5 (M 50, 75, 100) is used. Use a stronger cement does not make sense, besides, it will cost several times more expensive.
• To get a solid "preparation" it is enough to lay a concrete cushion 10 cm thick (provided that the groundwater does not predominate on the site).
• Before laying a concrete mixture, it is necessary to pour a thin layer of sand or crushed stone into the bottom of the excavation or trench.
• If the reinforcing frame is not used when installing the concrete cushion, then the optimum thickness of the base will be 15-20 cm.

• Due to reinforcement of the base, the ground part of the building will be located on a reliable base. For armopoyasa used metal rods with a cross section of 8 mm. The bars are installed vertically and should protrude about 25-30 cm above the surface. In this case, the thickness of the "preparation" can be reduced by 6-10 cm.

Mounting of the foundation

Let's say you plan to build a house on a plot with a rather loose ground and an elevated water table. To do this, perform the following steps:

1. Determine the highest point of groundwater - "preparation" is better to do it to this level. Some mount "training" in such a way that it protrudes beyond the underground structure by 10 cm.
2. Smooth and tamp the soil.
3. Pour large sand onto the bottom of the excavation, spread it over the surface and tamp well. For better effect, you can also lay a layer of rubble.
4. Above the sand bed ruberoid or polyethylene.
5. Lay the armo frame with cells 60 x 60 cm.
6. Install the guides, it will be more convenient for them to level the liquid mixture.

1. Mix cement, gravel, sand and water until a uniform, thick mass is obtained.
2. Pour concrete mortar and level it over the lighthouses using the rule.
3. After the base solidifies, treat the surface with bitumen.

Useful! In order not to use expensive drilling equipment after solidification of the monolith, it is recommended to think through the openings for communication during the laying of raw concrete.

In custody

Depending on the type of construction, you can lay sand, gravel or concrete "preparation". Such a pillow will give the entire structure additional strength and protect the foundation from groundwater.