Backfill under the foundation: varieties, features of choice

Backfill under the foundation: varieties, features of choice Why do you need a bedding under the foundation, and what it happens. When looking for information and tips on how to equip a foundation with your own hands, you probably came across such a concept as pouring under foundation. This is an important component in construction, so it is worth considering in more detail what functions it performs,

what it should be and what materials it can be made of.

General information about what is bedding

As you know, the foundation is the foundation of the house, and not a simple foundation, but the main and most important part throughout the construction process of a private house. If, for some reason, the foundation is made poorly or even of poor quality, then without fulfilling the important building rules of the standards, it will soon become unusable, and it will simply be impossible to live in the house.

In addition, the frames on the windows will begin to warp, the walls will crack, and the doors will no longer close normally, which can lead to the formation of drafts.

It is for this reason that it is very important to make a foundation that will be of high quality, comply with all the rules and regulations. One of the guarantees that the base will turn out to be strong, strong and reliable, that it will be able to stand for many years without deterioration in performance, is the competent and high-quality manufacturing of the bedding. It is thanks to her that reliability and durability for housing in general will be ensured for the foundation.

What should be the bedding

Backfill under the foundation: varieties, features of choice Now you have learned that filling under the concrete foundation is an extremely important and necessary element during the construction of various structures and buildings.

You should figure out how to make a bedding that will comply with all the rules and regulations. To begin with, you should find out that the bedding, which is also called a substrate and a pillow, is usually installed under the strip foundation. To create it, you should dig a trench of a suitable size in advance. If you look beyond the building requirements and norms that are applicable abroad, you will see that European experts advise making a foundation cushion with a thickness of 0.25 meters.

He believes that this is quite enough so that the foundation and bedding can fully perform all intended functions.

Now let's return to Russian realities, where European norms are not always acceptable. If you look at the experience of builders in the homeland, then almost everyone will tell you that the thickness of the bedding for the foundation will depend on what type of land on the site. Depending on what the features of the soil are, the thickness of the substrate can be from 0.3 to 0.

6 meters, and in special cases, in order to create additional insulation and safety net, the thickness of the pillow is made up to 0.8 meters.

Please note, that the greater the thickness of the filling under the strip foundation, the less in the future the foundation of the house will deform and collapse, which most often occurs due to heaving of the soil ...

The substrate can be made of crushed stone, sand and concrete, although most often only sand is used for the arrangement. Such a sand cushion needs to be tamped thoroughly and tightly. In addition, when laying such a pillow, it should be tamped gradually, in layers, and this is done so that in the future there is no shrinkage and deformation of the foundation of the structure. In the photo you can see the device of a monolithic slab foundation on a sand cushion.

It should be borne in mind that when creating a backfill under a strip or pile foundation, the selected material should be gradually poured, that is, in layers with a thickness of 0.

2 meters, and then carefully tamped using special tools like rollers or an area vibrator. The density of the finished substrate for the foundation should be no less than 1600 kg / m 3 .

You should also pay special attention to the fact that sometimes builders use a material such as clay to build a sand cushion, and for this, a layer of it is tamped into the dug hole. According to these experts, clay helps protect the foundation of the house if, for some reason, groundwater begins to rise, but in fact this is not at all the case. In reality, water will be trapped under a layer of clay and will not reach the foundation, but this is even harmful, since it will contribute to the increase in the heaving of the soil.

Preparation for the installation of the basement for the foundation

A pillow of sand, crushed stone or concrete for the foundation has several extremely important functions, namely:

  1. Water drainage. The foundation sand cushion helps to ensure that water that can begin to accumulate under the foundation is effectively drained, which will significantly reduce the impact of soil heaving forces.
  2. Uniform load distribution. Backfill helps to create an even distribution of pressure from the foundation in the house behind the ground, and also helps to increase the resistance of the foundation several times and serves to level it.

If a basement or any other basement will be arranged in your house, we advise you to connect the bedding with the base of the house by installing vertical reinforcement or using a profiled connection.

The foundation, made on a sand bed, must be waterproofed from above. If the house is built on the ground, which is subject to strong heaving, then on top of the foundation it should be reinforced for the foundation, namely, an armored belt made of iron with concrete.

If you are planning the construction of the frame structure of a house, then special carved pins, which are called anchors, must be bricked up in the base tape itself.This makes it possible to provide excellent adhesion between the frame walls of the house and the base, which will be characterized by the design features. Anchors are also required for use when installing reinforcement that will anchor the foundation of the house with a reinforced belt between floors.

Such fittings should be installed strictly vertically.

What sand to use?

In fact, filling under the foundation of sand is a base, that is, the base of the foundation. For this reason, it should only be done after the foundation trench has been dug. The depth of the trench, as already mentioned, will depend on the composition of the soil on which the house is to be built. When it is ready, it needs to be further deepened by 0.

15-0. 3 meters and cover with a layer of sand. In certain sources, where it is told about the manufacture of the substrate, it is recommended to use medium-fraction and fine-fraction sand for filling. But real experts recommend buying only coarse-grained sand for these purposes, since over time the fine fraction will begin to settle, but large grains of sand can retain their excellent qualities. You can also use ordinary river sand, which is classified as a middle fraction.

If, for some reason, wet sand gets into the trench, then it does not have to be tamped down, as it will be compacted by itself. If you take dry sand, then be sure to moisten it and tamp it thoroughly. In this case, it should be poured in portions, and after each sand filling, tamp. The quality of the bedding for the foundation can be easily checked - if a person walks over such a pillow, and there are no traces left, then you have tamped the substrate wonderfully.

Also, do not forget about the role played by the level of occurrence of the level of occurrence of groundwater.

For each region, the values ​​are different, and if it is higher in the place of the foundation, then the thickness of the backfill under the foundation should be increased. It is also worth paying attention not only to the evenness of the substrate, but also to the horizontal position. This can be checked using a building level. Before filling the sand, builders advise laying geotextiles or roofing felt on the bottom of the trench. The task of such a bedding is to ensure that the sand does not mix with the ground.

Step-by-step instructions for creating a sand bed

Interestingly, sand bedding has a low cost, and for this reason this option is ideal for those who wish at least to save somewhere during construction. In addition, it has a relative ease of creation, but despite the low prices, such a foundation under the foundation perfectly copes with many extremely important tasks. Its main advantage is that it can provide a moderate, not more than the standard, load on the foundation, or rather on its lower part, and also helps to protect the foundation from the negative effects of underground waters.

Sometimes there are situations when in a hole that was dug for the foundation, if a layer of earth that is not suitable for construction work. Such cases are far from uncommon, and if the same happened to you, then you should only remove unnecessary soil and put sand in place.

The finished sand pillow should be carefully leveled, and this must be done extremely carefully so that there are no dips and surpluses. Due to this, you will achieve the fact that the fluctuation of the material will disappear. Tamping should be done using a special tool - a vibrating plate. If possible, we advise you to abandon the use of outdated tamping methods, and remember that with the help of improvised means, it will not be possible to achieve such a high-quality and accurate result as with the help of specialized equipment. During the process, the sand pillow will need to be moistened with water, since it is thanks to the water that the sand layer will become as dense as possible.

What role does the groundwater level play?

If you nevertheless decide on a sand bed for a strip foundation, you should definitely take into account the fact that how deep the groundwater lies, and what level it rises in spring. For this reason, we are attaching you a foundation plan, depending on how the groundwater is located. If the groundwater is very close to the surface, then a drainage layer should be made under the bedding for the foundation. If it is not done in order to save money, then the sand substrate will soon be washed out, and this will naturally harm the foundation and the housing as a whole.

It turns out that the sand cushion is ideal for such cases:

  • If the groundwater is not very high in relation to the ground.

  • If the house will be built of light materials such as frame, expanded polystyrene, foam block. The sand bed will not be able to withstand too heavy loads.
  • If you are planning to build a one-story house. In multi-storey construction, structures are heavy, and during their construction it is better to use other types of bedding, which are really adapted to such loads.

Let's consider how to make a bedding for a foundation from rubble + video.

The order of the crushed stone filling device

This type of foundation under the foundation has greater strength compared to sand. Crushed stone acts as the main filler material, and before you start making a crushed stone pillow, you should prepare a layer of another material, which is smaller. The best option would be river coarse sand, which will need to be covered in a layer with a thickness of 0.1-0. 15 meters.

After that, it needs to be leveled and tamped well. This stage of work should be performed in a similar way to creating a sandy foundation cushion. On a well-compacted layer of sand, pour a layer of crushed stone, which in height should be no more than 0.25 meters.After the material is filled up, it should be leveled and tamped well.

It is also important to ensure that there is at least a minimum of free space between the individual pebbles, and it is better to tamp with the help of vibrating plates. The top layer of backfill should be placed at the ground level (i.e. at the edge of the trench). It is from this mark that the foundation of the building will begin.

The calculation of the amount of bedding should be performed taking into account the fact that, according to building codes and regulations, each side of the pillow should be about 0.2 meters larger than the foundation. A crushed stone bedding is perfect for country houses of any area, number of storeys and types. The material that will be used during the construction of the building will also not matter.

The device of the concrete substrate

The concrete pillow has the best strength and reliability indicators, but it also has a special drawback - high cost.

On the other hand, such a disadvantage can be fully compensated by the durability of the structure.

Concrete substrate is made in the following sequence:

  1. Backfill under the foundation: varieties, features of choice For first, the soil should be leveled, and then crushed stone should be laid on the ground, its layer should be 0. 1 meter, carefully tamp it. It is best to do this with vibrating plates.
  2. Form wooden planks around the entire perimeter of the pillow.

    Make sure that the height of the formwork is no more than 0.3 meters, that is, it coincides with the thickness of the base. Naturally, this is provided that the mortar is poured into the level with the upper edge of the formwork. It is required that the top elevation of the concrete base is located where the foundation itself will begin.

  3. To increase the strength and durability, we propose to perform the reinforcement of the substrate from concrete, and to do this using steel rods with diameters of 0.

    8-1. 2 cm.

  4. When the installation of the reinforcement is ready, you can start pouring the concrete. The concrete grade should be selected individually for your case, since it all depends on the weight of the future structure.
  5. The resulting structure should be well tamped and done with a construction vibrator.

And the main thing to remember is that the dimensions of the concrete cushion for the foundation should be larger than the foundation, this is extremely important. It is not difficult to determine the size - the area of ​​a correctly executed substrate will protrude from under the finished foundation by about 15 cm on each side. A foundation cushion made of concrete is considered the most reliable and durable. It can be used to construct buildings with an unlimited number of floors and sizes. The device for filling under the strip foundation is an extremely important and responsible process, and a properly made pillow is the best guarantee that you will be able to live without problems in a house built with your own hands for many years.

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