Foundation pillows are called special supports designed to stabilize the soil under various buildings and structures. Such elements are an indispensable part of the construction of the foundations of both urban high-rise buildings and private houses. In addition to the stabilizing effect, such pillows also have a protective effect. If they are present, the foundation of the house does not come into contact with groundwater, and therefore is not subject to destruction. The dimensions of the foundation pillows can be different. The same applies to their physical and mechanical characteristics.
Main varieties
Pillows can be used in the construction of residential and industrial buildings:
- sandy and gravel;
- concrete and reinforced concrete.
Both of these varieties are laid under foundations quite often. The advantage of the first type of pillows is their low cost, good shock-absorbing properties and ease of arrangement.
Concretedesigns of this variety are, of course, more expensive and more difficult to install. However, such pillows give the base of the building more stability, making it more reliable and durable. Such foundation pads for strip foundations may have different sizes.
Characteristics of sand and gravel pads
Shock-absorbing layers of this type are usually arranged only under the foundations of low-rise private country houses. Pillows of this variety are laid both under slab and under strip bases. Such a stabilizing layer is also provided under the supports of columnar foundations.
The simplest and cheapest type of house foundation substrate is sand. However, you can only equip it:
- on sites with deep groundwater;
- under light buildings.
Crushed stone pillows have a higher degree of density. They are poured out of material of different fractions. Previously, under such pillows, a small layer of river sand is applied to the bottom of the trench or pit.
Requirements for the arrangement of sand and gravel pillows
Substrates of this type are poured under the foundations of country houses in compliance with the following standards:
- the thickness of the sand stabilizing pad should not be less than 30 cm and more than 80 cm;
- the thickness of the leveling layer of sand under the gravel cushion should be 15 cm;
-
the thickness of the gravel pillow itself should be at least25 cm.
The dimensions of this type of foundation pads are in most cases equal to the area of the tape itself or the base plate of the house or the cross section of the supporting pillars.
It is believed that if the soil on the site is weak, it is better to equip a combined gravel-sand substrate under the foundation of the house. The ratio of materials for backfilling trenches in this case is defined as 60% to 40%. In any case, pillows made of bulk materials during the arrangement should be carefully compacted. For reliability, this operation is recommended to be carried out using a vibrating plate.
Concrete structures
This type of pillows is mounted mainly only under heavy high-rise buildings and structures. Most often, reinforced concrete structures are used to give strength to foundations and stabilize them. Such pillows have greater strength and, accordingly, service life. Reinforced concrete pillows are laid during the construction of high-rise buildings, of course, only under strip foundations.
When installing the foundations of houses, both stabilizing structures cast in place and ready-made factory ones can be used. Both types of substrates are considered quite reliable.
Requirements for pouring concrete pads
This procedure is performed according to standard technology. That is, a pillow is poured under the foundation as follows:
- at the bottom of the trenches, a leveling sand cushion is pre-equipped with tamping water;
- into the trenchformwork and reinforcing cage are installed;
- concrete mixture is being poured into the pillow.
When arranging such a stabilizing structure, it is necessary to comply with the following SNiP standards:
- the thickness of the reinforcing sand and gravel layer should not be less than 30 cm;
- the same minimum height is provided for the concrete substrate itself.
In terms of size, the foundation pillows of this type surpass the footprint of the very foundation of the house. According to the regulations, the width of the stabilizing reinforced concrete structure should be 15 cm more than the same indicator of the base of the foundation.
Reinforced concrete foundation pads: dimensions according to GOST
The advantages of such substrates include primarily increased strength and high installation speed. The only drawback of pillows of this type is the complexity of transportation and the need to use special equipment during installation. Such substrates are mounted under the fill, as well as under the prefabricated strip foundations.
In the manufacture of reinforced concrete structures at enterprises, among other things, certain standards are mandatory. Regulates the dimensions of foundation pads GOST 13580-85. According to this document, such structures can have a height of 300 or 500 mm.
The width of products of this type varies between 800-3200 mm (in increments of 200 mm). The length of reinforced concrete pillows depends on their width. Define thisindicator for products of standard size can be according to special tables. For plates of different widths, this figure is 780, 1180, 2380 and 2980 mm (in different variations).
Types by bearing capacity
Foundation pillows FL dimensions according to GOST 13580-85, thus, may be different. But there is another indicator, taking into account which the choice of such products can be made in the construction of houses.
Pillows of this type can be made from different materials and using different technologies. Accordingly, their bearing capacity may not be the same. In this regard, all reinforced concrete ready-made foundation pillows are classified into 4 large groups. You can determine how strong such a block is by its marking. The higher the class of the product, the greater the bearing capacity it differs.
How they are marked: decryption
It is possible to determine the purpose of a reinforced concrete slab of this type as a foundation cushion by the designation FL. Regulates the labeling of such products GOST. FL 16.24-3-P.
According to the designations provided by the manufacturer, you can find out, among other things, the dimensions of the foundation blocks-pillows. The marking of such products is deciphered as follows:
- the first two digits after "FL" - the width of the product (for example, 16 - 1.6 m);
- second two digits - pillow length;
- next digit is the bearing capacity class (1, 2, 3 or 4).
If the labeling of the plate additionallythe letter P is indicated, which means that it is made of concrete with low water permeability. Such products can also be used on wet soils.
Installation technology
According to the bearing capacity and size of the foundation pads FL, thus, can vary significantly. But in any case, when installing such structures, certain technologies must be observed without fail.
The blocks of the strip foundations themselves are marked as FB. According to the regulations, in the construction of buildings and structures, it is supposed to use FL slabs made using the same building materials as FB.
Reinforced concrete foundation pads are being installed as follows:
- marking is being carried out on the site and a trench is being dug;
- the bottom of the trench is compacted using special equipment;
- laying waterproofing material;
- a leveling sand and gravel pad is poured on the bottom of the trench;
- the bottom substrate is also carefully packed;
- FL slabs are delivered to the construction site;
- with the help of a crane they are installed in a trench;
- FL is being reinforced;
- with dressing, the blocks of the foundation itself are installed;
- pillow and foundation walls are waterproofed;
- backfilling trenches in progress.
When installing pillow blocks, builders must use a level. After all, the upper plane of the finished foundation must be absolutely horizontal.
