How to make a pillow under the foundation. How to make a foundation pillow yourself.

Any foundation definitely needs a foundation that protects it from impact groundwater or the forces of frost heaving. However, for blocks, the usual 5 cm layer of compacted sand will not be enough, because in this case the pillow performs another function. Since they are produced of small width - only 30-60 cm, the weight of the entire building is transferred through them to a narrow strip of land. As a result, uneven and severe soil subsidence can occur. To prevent this from happening, the support area should be increased to reduce the load per unit area. It is for this that a foundation pillow is arranged, which can be monolithic or prefabricated.

Fig. 1 Location of the pillow in the foundation

What types of pillows can be installed

FBS blocks can be arranged 2 types of pillows: prefabricated and monolithic... To install any type of pillow, it is necessary to dig a pit and carefully level its bottom. The width of the pit should be such that the installation of the blocks would not cause difficulties. Work begins with a breakdown of the foundation axes.

Figure: 2 Buildable foundation cushion

Prefabricated pillows are made from factory trapezoidal elements marked with FL (see). The base of such elements has a width of 60-320 cm, a height of 30 cm. The main purpose of blocks for a strip foundation is to expand the sole under the foundation base. On sandy soils, trapezoidal products are laid directly on the prepared soil, on others - on sand pillow... The width of the pillow is made 20 cm larger than the foundation itself. PL fit in this way:

• sand is poured up to 10 cm and carefully leveled;
• the first row is placed from trapezoids;
• the second row is laid by the blocks themselves with the offset of the side seams.

In low-rise construction or if it is planned to build an object from gas silicate blocks, FL slabs can be laid at intervals of up to 70 cm, filled with compacted soil or mortar (the so-called intermittent laying). With this installation technology, you can save up to 20% of the blocks. In this case, the second row is placed so that the blocks are located above the voids. Intermittent laying is not allowed when working on soft soils.

If the length of the FL is not a multiple of the length of the side of the house under construction, the resulting gaps are filled with additional blocks. It is important to leave a distance between FL for laying pipes and other engineering systems... Also, in order to correctly make a pillow for the foundation and save a lot of time, it is recommended to use the longest blocks.

Monolithic pillows under foundation blocks a little more time consuming to fill:

1. Gravel base arrangement;
2. The formwork is done as for the strip foundation;
3. Reinforcement is made with 12mm reinforcement along the lower edge, the indent from the base is 70 mm, the second row of reinforcement is fixed 30-40 mm from the upper level;
4. Pouring concrete with obligatory bayonet or vibration.
5. Drying and removing the formwork.
6. Waterproofing works.

A correctly calculated cushion for a monolith foundation has the same characteristics as a factory made one. But it takes much longer.

Figure: 3 Monolithic foundation pad

Single-row foundation cushion

A single-row foundation of blocks is made for light buildings (frame frames, baths). If the building is light, but the soil is heaving, then the single-row foundation is slightly strengthened. Laying:

• 30 cm of gravel and sand to create a pillow;
• 10 cm monolithic reinforced tape;
• a number of blocks;
• belt up to 20 cm made of monolithic reinforced concrete.

It is quite simple to make the correct pillows for the foundation of FL and FBS blocks, and a team of unskilled workers can cope with their device.

Before starting work on the arrangement of the prefabricated strip foundation, it is required to draw up an executive scheme. With the help of the scheme, the subsequent work on the laying of FL-plates and FBS-blocks will be carried out. Knowing the dimensions of the slabs strip foundations and block sizes will help you map out as accurately as possible.

In this document, the tables show the dimensions of the foundation blocks and slabs standard sizes, produced at reinforced concrete plants and KSM-ah. Each product is marked, the inscription on the product consists of alphabetic and numeric symbols. Each symbol carries information about the design features and dimensions of the foundation block or foundation slab.

Foundation block marking

Marking starts with a few letters. Depending on the application by design, the elements of the zero cycle are divided into:

• F - reinforced concrete and concrete from heavy concrete for columns (so-called glass type);
• FL - reinforced concrete made of heavy concrete for the installation of strip foundations;
• FBS - concrete solid unreinforced for the construction of basement walls, technical underground floors and foundations;
• BF - reinforced concrete tape made of heavy concrete for the construction of external and interior walls buildings of industrial and agricultural enterprises;
• FR - reinforced concrete from heavy concrete under three-hinged frames;
• FBP - foundation concrete hollow.

Subsequent numbers mean the dimensions of the foundation block in decimetres, rounded to the nearest whole number: length, width and height in decimeters or width and length (for FL). The first number is the length, the second is the width, and the third is the height of the foundation block.

Table 1. Dimensions of FL foundation blocks

	Brand	Dimensions, mm			Weight, t	Concrete consumption, m 3
		L	B	H
	FL6-24 ...	2400	600	300	0,93	0,37
	FL6-12 ...	1200	600	300	0,45	0,18
	FL8-24 ...	2380	800	300	1,15	0,46
	FL8-12 ...	1180	800	300	0,55	0,22
	FL10-30 -...	2980	1000	300	1,75	0,69
	FL10-24 -...	2380	1000	300	1,38	0,55
	FL10-12 -...	1180	1000	300	0,65	0,26
	FL10-8 -...	780	1000	300	0,42	0,17
	FL12-30 -...	2980	1200	300	2,05	0,82
	FL12-24 -...	2380	1200	300	1,63	0,65
	FL12-12 -...	1180	1200	300	0,78	0,31
	FL12-8 -...	780	1200	300	0,50	0,20
	FL14-30 -...	2980	1400	300	2,40	0,96
	FL14-24 -...	2380	1400	300	1,90	0,76
	FL14-12 -...	1180	1400	300	0,0,91	0,36
	FL14-8 -...	780	1400	300	0,58	0,23
	FL16-30 -...	2980	1600	300	2,71	1,09
	FL16-24 -...	2380	1600	300	2,15	0,86
	FL16-12 -...	1180	1600	300	1,03	0,41
	FL16-8 -...	780	1600	300	0,65	0,26
	FL20-30 -...	2980	2000	500	5,1	2,04
	FL20-24 -...	2380	2000	500	4,05	1,62
	FL20-12 -...	1180	2000	500	1,95	0,78
	FL20-8 -...	800	2000	500	1,25	0,50
	FL24-30 -...	2380	2400	500	5,98	2,39
	FL24.24 -...	2380	2400	500	4,75	1,90
	FL24.12 -...	1180	2400	500	2,30	0,91
	FL24.8 -...	780	2400	500	1,45	0,58
	FL28.24 -...	2380	2800	500	5,90	2,36
	FL28.12 -...	1180	2800	500	2,82	1,13
	FL828-8 ...	780	2800	500	1,80	0,72
	FL32.12 -...	1180	3200	500	3,23	1,29
	FL32.8 -...	780	3200	500	2,05	0,82

The brand of the slab is assigned by the project according to the value of the design pressure on the base under the base of the foundation, which is determined by dividing the calculated vertical uniform linear load (with a load safety factor of 1.0) by the width of the slab. The reinforcement and concrete grade of the slab are also assigned by the project.

Table 2. Dimensions of FBS foundation blocks

	Brand	Dimensions, mm			Weight, t	Concrete class	Consumption of materials
		L	B	H			Concrete, m 3	Steel, kg
	FBS24.3.6	2380	300	580	0,97	B7.5	0,406	1,46
	FBS24.4.6	2380	400	480	1,30	B7.5	0,543	1,46
	FBS24.5.6	2380	500	580	1,63	B7.5	0,679	2,36
	FBS24.6.6	2380	600	580	1,96	B7.5	0,815	2,36
	FBS12.2.6	1180	200	580	0,32	B7.5	0,133	0,76
	FBS12.3.6	1180	300	580	0,485	B7.5	0,203	0,76
	FBS12.4.6	1180	400	580	0,64	B7.5	0,265	1,46
	FBS12.5.6	1180	500	580	0,79	B7.5	0,331	1,46
	FBS12.6.6	1180	600	580	0,96	B7.5	0,398	1,46
	FBS12.2.3	1180	200	280	0,16	B7.5	0,066	0,38
	FBS12.3.3	1180	300	280	0,24	B7.5	0,100	0,38
	FBS12.4.3	1180	400	280	0,31	B7.5	0,127	0,74
	FBS12.5.3	1180	500	280	0,38	B7.5	0,159	0,74
	FBS12.6.3	1180	600	280	0,46	B7.5	0,191	0,74
	FBS9.2.6	880	200	580	0,235			0,36
	FBS9.3.6	880	300	580	0,35	B7.5	0,146	0,76
	FBS9.4.6	880	400	580	0,47	B7.5	0,195	0,76
	FBS9.5.6	880	500	580	0,59	B7.5	0,244	0,76
	FBS9.6.6	880	600	580	0,700	B7.5	0,293	1,46

The foundation is not only the foundation of any building, but also the guarantor of the durability and strength of the building. Exactly right choice and adherence to a strict sequence of work, as well as a competent selection of materials used in the construction of the foundation, guarantee its reliability and compliance with the required quality standards. The main purpose of this part of the house is to provide the future structure with a stable and strong site. A properly prepared and laid sand and gravel cushion under the foundation is able to provide it with a lesser degree of sediment. Thus, a reliable pillow helps to significantly improve its quality indicators.

In the event that the construction of the foundation is carried out without observing the necessary building codes and contrary to the existing and time-tested rules, the constructed building in a very short time can become completely unsuitable for living. At the same time, cracks appear on the surfaces of the walls, the window frames are warped, the doors cease to close tightly. All this leads to the appearance of mold, dampness, drafts.

Renovated and finished premises are losing their attractiveness. Owners of such unfortunate buildings have to invest additional funds, time and money in unforeseen repairs.

Compliance with all foundation construction requirements will help to avoid disappointment. And its correctness depends on how exactly the sand and gravel cushion was made for the foundation. It is rightfully considered the key to a strong and solid foundation. The pillow ensures the complete absence of contact between building materials and construction objects with the foundation itself, which, in turn, excludes the appearance of various deformations. Thanks to the presence of a well-chosen and prepared pillow, the building (at its very bottom) rises high in terms of groundwater.

A mixture of sand and gravel is one of the most popular and commonly used building materials... Both of these components, mixed in strict accordance with the recommended proportions, are very often used for the construction of homes, shops and other buildings. This seemingly simple composition is one of the most the best options the basics. It guarantees the strength of the mix of concrete or cement mortar.

Why do you need a foundation pillow?

Those who are thinking about making the foundation for the construction themselves should pay attention to the clearly formed building rules regarding this issue. First of all, it is important to comply with all the requirements for such a stage of work as the device of a sand and gravel cushion. In addition to a cushion made of a combination of sand and gravel, cushions for a foundation made of concrete and crushed stone are common. As a rule, a concrete pad is required only when performing a reinforced belt under the FBS blocks or when further expanding the foundation walls.

The sand and gravel pillow is made on construction sites with weak soil. It is important to remember that in no case should sand dust or fine-grained sand be used to form it. The ready-to-use mixture must consist of gravel and sand, which have an average particle size. After the pillow from this composition is laid, it will give minimal shrinkage, for which it is necessary to perform a thorough compaction. Such a foundation for the foundation will perfectly withstand the load of not only a medium-sized house built of frame building materials, beams or logs, but also a structure of a large area, for example, with an attic or second or third floor.

When building a sand and gravel support, you can use this option for carrying out work:

1. dig a trench of the required width and depth up to the level of dense soil layers;
2. in the moat, which thus turns out, it is necessary to fill in coarse-grained river sand;
3. sand should be covered in layers and in small portions. Each layer should be 15 cm thick;
4. after laying each new layer, it must be spilled with water;
5. all layers are compacted using a special compaction technique;
6. the finished support should be 10 mm wider than the planned width of the future building.

The need for a sand and gravel cushion during construction, not only low-rise, but also larger, is due to its relatively affordable cost, high degree of durability and the ability to carry out work on their own, without the help of professional builders. However, it should be borne in mind that such trifles as cleaning the trench after the excavator, backfilling with buckets or a wheelbarrow of sand and gravel, manual watering of all layers with water will require serious physical efforts from workers. An attempt to involve household or friends in the process may be quite justified.

DIY sand and gravel pillow

Every experienced master builder knows what a sand and gravel pillow is for. Such a foundation for the foundation is capable of ensuring the building subsequently built fully functioning without defects and damage. It must be remembered that layers of sand and gravel mixture are stacked in layers, but in different thicknesses of each layer. The fact is that this issue is fundamental for each individual type of soil. In no case should the layer of sand and gravel be less than 5 cm thick.Many builders do not welcome a pillow thickness greater than 25 cm.

It is advisable to equip the pillow under the entire building area. It is this method of laying that ensures the most uniform settlement of the structure. The width of such a cushion should be wider than the width of the foundation base by at least 30 cm. Thus, the structure is supported over its entire surface area. When laying a sand and gravel cushion, it should be compacted so intensively that it acquires a density equal to 1.6 g / cm3 of the density of soil layers.

When doing this work yourself, monitor the quality of the building materials used. For example, the presence of even a small amount of clay admixture in the sand can lead to serious unpleasant consequences. If water gets into such a pillow, it will begin to swell. Therefore, control the composition and condition of the materials used, and also, be sure to follow the recommendations and step by step instructions at all stages of work.

Many novice builders think about when and how to make a sand and gravel pillow with their own hands. The solution to this problem is quite accessible to everyone who wishes. And since laying the foundation is the first step towards the construction of any building, a serious and responsible approach is required for its implementation. The depth of the foundation is primarily determined by the level of water flow in the ground. At a great depth of laying the base, one cannot do without a sand and gravel cushion.

Having decided what a sand and gravel cushion is, you can start installing it, which basically boils down to the following:

• it resembles a kind of "cake" with layers of sand and gravel (you can use crushed stone);
• the first layer in a dug trench (foundation pit) is a rubble, which will provide additional strength;
• the second layer is coarse river sand, which, after distribution over the entire surface, must be leveled, watered and tamped;
• the third layer, at least 20 cm thick, is gravel. After laying it is tamped using a vibrating plate;
• ready-made layers are covered with a layer of sand equal to 20 cm. After it is watered with water, it settles on gravel.

This technology must be followed layer by layer until the wet sand has nowhere to settle. After the completion of the work on the manufacture of the pillow, you can start building the foundation.

The subtleties of the construction of a shallow foundation

The shallow foundation is a monolithic tape, mainly made of reinforced concrete. The height of such a tape is from 40 to 60 cm, and its width is 35 to 50 cm. These indicators depend on the thickness of the walls and the materials from which they are built. Laying such a base under the building is carried out under all external and internal load-bearing walls.

A very important point in the construction of such a foundation can be called the installation of the correct pillow, in which exclusively non-heaving components should be used. Sand and gravel are ideal ingredients. Moreover, the ratio of these components can be approximately as follows:

• river sand of large fractions - 60%;
• gravel - 40%.

This mixture replaces the soil and is laid on the bottom of the prepared trench. Most often, the trench depth is about 50 cm. All laid materials are tamped. This backfill significantly reduces the impact on the foundation of heaving forces during frost. The sand-gravel mixture neutralizes and springs the impact on the base of the structure from below.

The advantages of a shallow foundation include its low cost and lack of great labor intensity. However, with this choice, the size of the future building is limited, for example, the walls should not exceed 7 m. As for the arrangement of basements, they are not provided for with this type of foundation.

Foundation pillows FL - dimensions according to GOST 13580-85

An indispensable element in the construction of industrial facilities, residential buildings and premises with heavy capital walls, powerful reinforced concrete floors - concrete foundation cushions... If a basement room or basement floor is planned at the construction site in accordance with the project, then a solid foundation is necessary. The construction of belt-type foundations is carried out using FL foundation cushions or, as they are also called, strip foundations.

Being the load-bearing element of the structure of the object, taking on the bulk of the building, pillows reinforced with steel mesh must be manufactured in strict accordance with the requirements regulated by GOST. The full name of the standard under number 13580 is "Reinforced concrete slabs for strip foundations."

Why is it necessary to strictly focus on this document, what is it? Let's consider in more detail in this article.

The information will be useful for those who are engaged in the construction or design of foundations and are interested in the strip foundation to meet all the characteristics provided for by the regulatory document.

Reinforced concrete foundation cushions are used in the construction of industrial, residential and public multi-storey buildings with heavy walls

Relevance of the standard

Despite the fact that GOST was developed in 1985, it has not lost its relevance at the present time. Foundation blocks perform a serious task related to ensuring the strength of the building, and are a particularly critical element of the building. The products represent a high-tech structure made of heavy concrete reinforced with steel reinforcement. Their responsible role in construction requires strict adherence to all the nuances of the manufacturing process. After all, blocks must have:

• high strength characteristics;
• frost resistance;
• corrosion resistance.

It is possible to ensure the whole range of necessary performance and bearing properties by strictly observing the provisions of the regulatory document that provides for all the mandatory requirements for products.

Document structure

The standard regulates a set of requirements for belt-type bases and foundations. The main element of this structure is a concrete pad, reinforced with steel reinforcement, which allows to increase the width of the support base, thereby reducing the specific load per unit area. The mandatory requirements for this responsible element are provided for by the standard, which regulates the following main points:

• Scope and conditions of use.
• Design features, technical characteristics.

FL foundation pillows are manufactured in accordance with GOST 13580 and are high-tech reinforced concrete structures made of heavy concrete

• Reinforcement specifics.
• Quality control technology.
• Transportation and storage methods.

Terms of use of products

In accordance with the standard, the foundation base can be used in various soils, both dry and with a high concentration of moisture. Features of the design, providing for the presence of steel reinforcement, limit the scope of the blocks in aggressive environments that can cause corrosion of the frame.

The standard allows the use of foundation cushions at the lowest possible ambient temperature - minus 40 degrees Celsius, and the design seismicity should not exceed 9 points.

Nomenclature series

You can select the types of blocks necessary for construction using the standard table. The product range is extensive. For each of the types, marking, geometric dimensions, the need for reinforcement, concrete are indicated.

FL brand slabs for prefabricated strip foundations

The shape, dimensions and reference weight are given in table 1:

Table 1. Shape, dimensions and reference weight of slabs

In accordance with the requirements of the project of the building being erected, with a block height of 30 or 50 cm, you can choose products of any required dimensions:

• length - from 0.78 to 3 meters;
• width from 0.6 to 3.2 meters.

The slabs differ in the shape of the lateral surface, which is flat with a width of 0.6 meters, and stepped for products with dimensions from 0.8 to 3.2 m. For transportation and installation, special lifting equipment is required, since the weight of the lightest blocks is about 400 kilograms, and the heavy ones - about 6 tons.

Deviations in the size of products are strictly regulated by GOST and, depending on the type of product, are no more than 15 millimeters in size and 10 millimeters in height. On the surface, deviations from flatness of more than 4 millimeters are not allowed.

Features of marking

Manufacturers of reinforced concrete products, according to the standard, must apply a special marking, which encodes the overall dimensions, perceived pressure, susceptibility to moisture penetration.

Most often, in practice, foundation blocks of the FBS and FL types are used.

Using the FL10.24-3-N slab as an example, we will deal with the coding. What information is indicated by the indices:

• The letters FL - designation of the type of reinforced concrete structure (strip foundation).
• Group of numbers 10.24 - characterize the dimensions of the slab, rounded in decimeters (respectively, width - 1000 mm, length - 2380 mm).
• Number 3 - informs about bearing capacitycorresponding to an average pressure of 0.35 MPa (3.5 kg / cm²) for a solid wall 16 cm thick. The standard divides products into 4 groups, which are differentiated by different forces perceived by the base of the slab at certain values \u200b\u200bof wall thicknesses.
• Index H - denotes the degree of moisture penetration into concrete products (in this case, normal). There is also a reduced and lower permeability, which are denoted by the letters P and O, respectively.

On the side surfaces of reinforced concrete products, in accordance with the requirements of GOST, the manufacturer is obliged to apply markings.

Reinforcement with reinforcement

Ensuring the required strength is achieved by reinforcement made according to one of the following design solutions:

• single layer mesh, wicker construction;
• welded double-layer mesh frame.

Foundation blocks mainly transfer the load to stable soil layers or to a prepared pad

The first option is used for narrow slabs up to 1.6 meters wide, and the second - for product sizes increased to 3.2 meters.

The standard obliges when installing a flat mesh or a three-dimensional reinforcing cage to maintain a distance from the reinforcement to the outer surface of at least 30 millimeters. A layer of concrete of the specified thickness will reliably protect the steel reinforcement from moisture penetration, the destructive effects of corrosion.

To ensure the immobility of the reinforcement, non-metallic gaskets should be used. Wire sizes differ depending on the design of the rigging devices, the number of attachment points. Its diameter ranges from 4 mm (for grade Вр – I) to 14 mm, corresponding to wire А – III.

The steel reinforcement, securely concreted in the cushion, comes out and forms a mounting loop. This element is required for movement during installation. A diagram of the installation of the lifting shackles is given in the appendix to this standard. The document regulates six options for fasteners, depending on the mass of the plate.

How is acceptance and quality checked?

After manufacturing, the foundation blocks are accepted by the service staff technical control in lots of up to 200 pieces. During acceptance tests, the dimensions, strength characteristics, and welded joints are controlled.

All blocks of this class are made of heavy grades of concrete, they must meet the requirements of GOST for bases and foundations

Both laboratory control methods and visual ones are used. The surface category, crack opening width and accuracy are selectively checked. Visually control the correctness of the designation, the presence of embedded elements, safety lugs.

The control of the rigging is carried out by loading the strapping brackets with the mass of the product during five lifting-lowering cycles. Integrity violation, breaks, cracks are not allowed. Three times the safety margin for the lashing eyes is required.

For product control, laboratory equipment, ultrasonic testing and other methods are used to check:

• Moisture absorption coefficient.
• Resistance to negative temperatures.
• Strength characteristics.
• Dimensional tolerances.
• Strength of welded joints.
• Waterproof.
• Marketable condition.
• The presence of a protective layer.
• The state of the reinforcement cage and embedded parts.

Features of storage and transportation

GOST requirements oblige to store products in a horizontal position, not to stack more than 2 meters in height. On delivery, cross pads are placed between the pillows at a distance of 20 to 75 cm from the edge of the product

Special requirements

In accordance with the recommendations of the standard, the production of plates at the manufacturing plant should be carried out according to the approved technology. The provisions of the document regulate serious requirements for the design of blocks for a number of characteristics:

• compressive and tensile strength;
• the quality of the components used in production;
• resistance to temperature changes;
• moisture absorption and permeability;
• the quality of welded joints;
• corrosion resistance;
• the formwork used in the manufacture;
• the brand of reinforcement used for the manufacture of safety brackets, embedded parts.

Foundation pillows should be made of concrete of special strength, with a density of up to 2.5 tons per cubic meter.

These are the main provisions that are regulated by GOST. Compliance with the requirements of the regulatory document guarantees the quality of the manufactured FL blocks, which are the main loaded element of the foundations of modern knowledge.