How to make a bedding under the foundation. Sand and gravel cushion for the foundation Sand and gravel backfill
The foundation is not only the basis 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 the 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 platform. A properly prepared and laid sand and gravel cushion under the foundation can provide it with less settlement. Thus, a reliable pillow helps to significantly improve its quality performance.
In the event that the construction of the foundation is carried out without observing the necessary building codes and contrary to existing and time-tested rules, a constructed building can become completely uninhabitable in a very short time. In this case, cracks appear on the surfaces of the walls, window frames become warped and the doors stop closing tightly. All this leads to the appearance of mold, dampness, and drafts.
The renovations and decoration of the premises lose their attractiveness. Owners of such unsuccessful buildings have to invest additional resources, time and money in unforeseen repairs.
Compliance with all requirements for foundation construction will help you avoid disappointment. And its correctness depends on how exactly the sand and gravel cushion under the foundation was made. It is rightfully considered the key to a strong and durable foundation. The cushion ensures the complete absence of contact between building materials and construction objects and the foundation itself, which, in turn, eliminates the occurrence of various deformations. Thanks to the presence of a properly selected and prepared cushion, the building (at its very bottom) rises high in relation to groundwater.
A mixture of sand and gravel is one of the most popular and frequently used building materials. Both of these components, mixed in exact accordance with the recommended proportions, are very often used for the construction of residential buildings, shops and other buildings. This seemingly simple composition is one of the most best options basics. It guarantees the strength of the concrete or cement mixture.
Why do you need a pillow under the foundation?
Those who are thinking about making the foundation for the building themselves should pay attention to the clearly formed building regulations regarding this issue. First of all, it is important to comply with all the requirements for such a stage of work as the installation of a sand and gravel cushion. In addition to a cushion made of a combination of sand and gravel, foundation cushions made of concrete and crushed stone are common. As a rule, a concrete pad is required only when used under FBS blocks reinforced belt or with additional expansion of the foundation walls. 
The sand-gravel cushion is made on construction sites with weak-bearing soil. It is important to remember that under no circumstances should you use sand dust or fine-grained sand to form it. The ready-to-use mixture must consist of gravel and sand, which have medium particle sizes. After a pillow made from this composition is laid, it will give minimal shrinkage, to ensure which it is necessary to carefully compact it. Such a base for the foundation will perfectly withstand the load not only of a medium-sized house built from frame building materials, timber or logs, but also of a large building, for example, with an attic or second or third floor.
When constructing a sand and gravel support, you can use the following work option:
- dig a trench of the required width and depth down to the level of dense layers of soil;
- in the ditch, which thus turns out, it is necessary to fill river sand coarse grade;
- sand should be poured in layers and in small portions. Each layer should be 15 cm thick;
- after laying each new layer, it must be spilled with water;
- all layers are compacted using special tamping equipment;
- the finished support should have a width 10 mm greater than the planned width of the future building.
The need for a sand-gravel cushion in construction, not only of low-rise buildings, but also of larger ones, is determined by its relatively affordable cost, high degree of durability and the ability to carry out the work with one’s own efforts, without the help of professional builders. However, it should be taken into account that such little things as cleaning the trench after an excavator, filling sand and gravel with buckets or a wheelbarrow, and manually watering all layers with water will require workers to invest serious physical effort. It may be entirely justified to try to involve family members or friends in the process.
DIY sand and gravel pillow
Every experienced master builder knows why a sand and gravel cushion is needed. Such a base for the foundation can ensure full functioning of the subsequently constructed building without defects or damage. It must be remembered that layers of sand and gravel mixture are laid layer by layer, but at different thicknesses for 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 cushion thickness of more than 25 cm.
It is advisable to install a cushion under the entire area of the building. It is this method of installation that ensures the most uniform settlement of the structure. The width of such a cushion should be no less than 30 cm wider than the width of the foundation base. Thus, the structure is supported over its entire surface area. When laying a sand-gravel cushion, it should be compacted so intensively that it acquires a density equal to 1.6 g/cm3 of the density of the 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 in sand can lead to serious unpleasant consequences. If water gets into such a pillow, it will begin to swell. Therefore, monitor 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 anyone who wants to do it. And since laying the foundation is the first step towards the construction of any building, a serious and responsible approach is required to its implementation. The depth of the foundation is primarily determined by the level of water flow in the ground. With a large foundation laying depth, a sand and gravel cushion cannot be used.
Having decided what a sand and gravel cushion is, you can begin installing it, which basically boils down to the following:
- it resembles a kind of “pie” with layers of sand and gravel (you can use crushed stone);
- the first layer in the dug trench (pit) is rubble, which will provide additional strength;
- the second layer is coarse river sand, which, after spreading over the entire surface, must be leveled, watered and compacted;
- the third layer, at least 20 cm thick, is gravel. After laying, it is compacted using a vibrating plate;
- the finished layers are covered with a layer of sand equal to 20 cm. After it is watered, it settles onto the gravel.
This technology must be followed layer by layer until the wet sand has nowhere to settle. After finishing the work on making the pillow, you can begin building the foundation.
Subtleties of constructing a shallow foundation
The shallow foundation is a monolithic strip, mainly made of reinforced concrete. The height of such a tape is from 40 to 60 cm, and its width is 35 – 50 cm. These indicators depend on the thickness of the walls and the materials from which they are built. Laying such a foundation under the building is carried out under all external and internal load-bearing walls.
Very important point The construction of such a foundation can be called the installation of the correct pillow, in which only components that are not subject to heaving should be used. The ideal components for it would be sand and gravel. In this case, the ratio of these components may be approximately as follows:
- river sand of large fractions – 60%;
- gravel – 40%.
This mixture replaces the soil and is placed at the bottom of the prepared trench. Most often, the depth of the trench is about 50 cm. All laid materials are subject to compaction. This bedding significantly reduces the impact of heaving forces on the foundation during frosts. 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 labor intensity. However, with this choice, the size of the future building is limited, for example, the walls should not exceed 7 m. Regarding the device basements, then with this type of foundation they are not provided.
Laying the foundation of a house is the first and most important stage of construction, but this is preceded by preparing the foundation under the entire building area on the site.
The type of foundation, its design and characteristics depend on bearing capacity soils at the construction site, as well as the strength of the house that will be built subsequently.
Even at the design stage, it is necessary to determine the properties of the soil and determine which backfill for the foundation, sand or crushed stone, will be relevant as preparation.
It is somewhat incorrect to raise the question of choosing a backfill for a foundation made of sand or crushed stone. The key to a strong and sustainable home is a strong and solid foundation, which must meet a number of requirements:
- High strength and density of the soil, capable of withstanding the distributed load of further development;
- Groundwater should not linger under the foundation, therefore the high drainage capacity of the soil is important;
- When wet or dry, the base should not lose its basic characteristics.
- It should not contain organically active components;
- The presence of flammable or plant residues capable of rotting is not allowed.
- Cold heaving of the soil is not allowed;
- Uneven shrinkage or deformation is not allowed.
In progress construction work the base should not deform even under the load of the involved construction equipment or construction activity.
The strength of the surface layer should be sufficient to accommodate all necessary elements, such as reinforcing frame, formwork, etc.
bedding device
Since it is not possible to select the type of soil on the site in advance, you should work with what you actually have. If the soil does not meet the specified requirements, a foundation filler is used from:
- sand;
- gravel;
- sand and gravel mixture (SGM);
- gruss (crushed fragmentary rock);
- crushed stone;
- skinny concrete.
Since the properties of each of the listed materials differ, as do the methods of their use, the choice of backfill should be made based on the final requirements for the base under the foundation.
The main conclusion: backfilling the foundation with sand or gravel is needed to adjust the properties of the soil on which the house will be built. It is part of the foundation preparation activities and is not an absolute component.
Anyway the type of soil is first determined optimal type foundation(tape, pile, monolithic slab etc.) and after that, if necessary, select the type of bedding that will be required.
High-quality training under strip foundation or monolithic slab is pouring the bottom of the pit with lean concrete to level the level and prepare a solid foundation. Sand or gravel are for the most part a low-cost alternative to reduce overall construction costs.
Sand
Simple and enough effective option foundation fillers. Well compacted mechanically the sand cushion is capable of taking on the same strength and density as the main soil, and at the same time is easily shaped to accommodate all the unevenness of the bottom of the pit. 
Advantages of sand for backfilling:
- With high-quality compaction, you can achieve a base strength equal to original value for soil;
- Fills all the unevenness of the pit well and transfers the load evenly;
- Sand retains drainage properties;
- Easily shaped and leveled;
- Does not require the use of heavy construction equipment.
Flaws:
- Weak mechanical strength transverse point load.
- Sand is washed away by groundwater over time.
Sand for backfilling is ideal when using ready-made reinforced concrete blocks and slabs, allowing the load to be transferred evenly over the entire base.
Sand for backfilling is selected from coarse and medium fractions without clay inclusions. Even with complete compaction, the drainage properties of the base are preserved, and cold heaving has almost no effect on the strength of the base.
The thickness of the bedding can range from 10 to 60-70 cm depending on the properties of the soil. The depth of soil freezing in many regions of the country exceeds 30 cm, and cold heaving can appear even under a well-insulated foundation during prolonged winter cold spells.
The optimal height for adding sand is considered to be 45-60 cm. Such a layer of sand is difficult to compact at a time, so the material is gradually filled in layers 5 cm thick and gradually compacted and necessarily moistened.
It is quite difficult to determine the required amount of water to moisten the sand. A common mistake is excessive moistening of the sand, from which the entire mass becomes plastic and diverges more to the sides of the tamper than becomes compacted.
The volume of liquid should be determined individually so that the sand is easily crushed in your hands, maintaining the shape of a cake. On the other hand, during mechanical compaction, water should not protrude on top of the sand.
The degree of sand compaction is determined quite simply. If on a prepared sand cushion there are no traces left when walking on it, which means the base is ready for further work.
Gravel
Medium and coarse gravel is used for backfilling in situations where the maximum throughput of the drainage layer should be ensured under the base of the foundation in combination with distributed drainage system oriented towards draining groundwater from the base of the foundation.
Gravel is often used as a cheap substitute for lean concrete when preparing and strengthening the soil for a foundation. To do this, it is compacted and mixed with the soil mechanically or manually.
However this is not The best decision, since without a binder, which can be cement, such a foundation is susceptible to erosion by groundwater with subsequent loss of load-bearing strength.
More often in demand is ASG - a sand and gravel mixture to form a level area under the foundation. In combination with sand, the mixture is easier to impart density and strength comparable to that of the parent soil on construction site, while maintaining the drainage capabilities of the bedding.
Advantages of gravel backfill:
- Low water capacity of the substrate, liquid is poorly retained in it, and the surface area of gravel for wetting is much lower than that of sand;
- The strength of the bedding and its high load-bearing capacity and resistance to erosion or lateral loads.
Flaws:
- Under heavy loads, even distributed, gravel bed can “sink”, reducing its own strength and the strength of the parent soil;
- It is difficult to level the bedding surface;
- When pouring concrete, part of the cement laitance falls aimlessly through the bedding, weakening the main body of the foundation.
If gravel is used for backfilling under a strip foundation or monolithic slab, then, of course, it should be pre-insulated to prevent the concrete from weakening. However, this often incurs more costs than using initially lean concrete.
Which is better sand or crushed stone
The requirements for preparing the foundation pit for the foundation require strict instructions in the construction project based on an analysis of the bearing capacity and properties of the parent soil.
The best preparation for a strip foundation or monolithic slab is lean concrete and only in some cases is it possible to replace concrete with sand, gravel or ASG to reduce overall costs. At the same time, sand has a wide range of advantages and is more practical. 
Gravel is suitable only in cases where high throughput if necessary, arrange a drainage layer with low water capacity. At the same time, it is difficult to isolate the bedding from the volume in which the foundation will be poured.
The gravel backfill goes well with pile foundations, where it is enough to remove excess moisture from under the base of the house, and at the same time there will not be a significant load on the bedding itself.
Under strip foundation
By definition, sand bedding is needed only if ready-made reinforced concrete slabs and blocks to distribute the load evenly along the base plane.
With the help of sand it is easier to level the bottom of the pit, and tamping gives the sand the necessary density and load-bearing capacity.
However, this is only relevant if it is possible to place a massive vibrating plate in the trench for mechanical rammer sand In most cases, it is safer to use a lean concrete footing to level the base and prepare it.
Sand is also relevant in case of significant differences in height along the bottom of the prepared trench. To reduce costs and reduce the volume of solution for the concrete base, sand or crushed stone is added with layer-by-layer compaction and moistening.
Under a monolithic slab
It is important to strictly level the base of the pit and prepare the soil for installation of the reinforcing frame and pouring. Either lean concrete or sand compacted in layers is used.
construction stages monolithic foundation
Sand is mainly used in cases where it is necessary to significantly raise the bottom of the foundation pit after removing the entire fertile soil layer to the base of the parent soil.
When forming the bedding, it is important to pre-distribute trays for water drainage, communication lines that will pass through the foundation slab, and also mark the required planes of the future foundation.
According to the requirements, a base is formed under the monolithic slab not strictly in one plane, but with a slight elevation in the center of the building and with a slope of 2-3% in all directions, for effective removal of moisture from the substrate of the future foundation.
Particular attention is paid to the quality of sand compaction. So, the density of the backfill for the foundation should be from 1.65 t/m3 and preferably not less than the density of the parent soil with an error within 0.05 t/m3.
The height of the backfill is determined as the difference between the level of the bare base of the soil after removal of the fertile layer and the design level of the foundation base.
Under a pile foundation
The backfill primarily performs the function of drainage to drain groundwater, and also acts as a substitute for the fertile layer of soil in order to remove the volume of material containing organic or combustible inclusions from under the foundation.
backfill device for pile foundation
For these purposes, it is best to use large and medium gravel and crushed stone. Expanded clay bedding is often used, which further increases thermal insulation properties grounds.
ASG is a high-quality, purified mixture of sand and gravel. Thus, sand-gravel mixture refers to non-metallic materials used in the construction of residential and industrial facilities, creating high-quality road surfaces, in the train road construction, when laying drainage layers, for leveling areas in landscape design, for making iron concrete products, used for construction panel buildings. Also adding ASG necessary to create a cushion for the construction of foundations, equipment of sites for the operation of special equipment and during road construction, for backfilling trenches and pits.
Can be natural and enriched. It is mined in quarries or from the bottom of reservoirs. Natural ASG contains at least fifteen percent gravel, and in an enriched mixture the gravel content can significantly exceed this figure. Enriched ASG differs in gravel content into five groups: 15-25%, 25-35%, 35-50%, 50-65%, 65-75%. The more gravel a mixture contains, the correspondingly harder it is. Gravel is added to the mixture artificially in production. The price of enriched PGS depends on the amount of gravel in it and its size. Both types of PGS are characterized by durability and resistance to physical influences, which contributes to their wide application. If you need such high quality materials, then construction company offers to buy and deliver all the necessary non-metallic construction materials: sand, crushed stone, gravel, bedding, ASG and others.
The backfill, as a rule, is made from non-heaving soil and instead of ASG, construction soil no finer than medium-grained is also used as backfill. The size of the bedding is determined by a special temperature calculation, and it is necessary to provide ventilation and thermal insulation so that it is not too large. ASG backfill is used for arranging a monolithic foundation, single- or two-story house. The installation of such a foundation begins with the development of a pit, compaction and creation of a cushion using ASG backfill, sand and gravel. Placed on top of it waterproofing material and poured with a small layer of concrete, then reinforcement is laid, and the pit is filled with a special concrete solution. The result is a single monolithic slab used for the basement floor.
Technology of construction of various structures on initial stage construction also almost always involves the arrangement of a site for work (this requires bedding). Filling sites and roads is an important stage of any construction. Thus, depending on the type of structure, climatic and geographical conditions, the filtration properties of the material largely depend on the quality and service life buildings, therefore, for arranging the canvas cushion, foundation device is used adding ASG, crushed stone, sand – High Quality. The technology consists of several stages:
- First, using a bulldozer or excavator, they remove upper layer soil to hard rock, this is necessary to insulate the base of the future structure.
- Then soil rollers are used to strengthen the soil and form a platform for subsequent work.
- The actual installation of the cushion and compaction is carried out using bedding with ASG, crushed stone, and sand.
- Additional backfilling of hard rock crushed stone and its compaction is possible.
The ISO Altair company offers to buy a sand and gravel mixture that meets the requirements of GOST 23735-2014. We deliver with our own fleet of vehicles, 7 days a week, without holidays or weekends. We supply up to 2000 cubic meters of sand and gravel mixture per day.
To order, we will make the required ratio of sand and gravel.
The price of PGS according to your parameters is discussed individually. Call!
Price for sand and gravel mixture
The table below shows the ISO Altair company's base prices for sand and gravel mixture.
| Photo | Name | 3 m3 | 10 m3 | 15 m3 | 20 m3 | 100 m3 |
|---|---|---|---|---|---|---|
| ASG enriched | 3350 | 1050 | 1000 | 950 | 900 | |
| PGS natural | 3250 | 1000 | 950 | 900 | 850 |
The Altair company has entered into dealer relationships with quarries where sand and gravel mixtures are mined, and therefore has set the lowest possible prices for this non-metallic material. The cost of a cubic meter of sand and gravel mixture depends on the volume of purchase. The more ASG a client orders, the more favorable the price. The numbers are reflected in the table.
ISO "Altair" is equipped with a fleet of vehicles. Therefore, the vehicle with the cargo is sent from the warehouse immediately after payment for the order. The transport department and order department operate around the clock. The client receives the sand and gravel mixture at the specified address within a few hours after placing the order. Each batch of ASG is certified.
This material is a mixture of gravel and sand. The fractionation of the sand-gravel mixture is heterogeneous: the diameter of the grains of sand and pebbles is not the same.
Sand and gravel mixture is an environmentally friendly natural material. Mined open method in quarries using excavators. This mortar rough, its use is limited. ISO "Altair", among non-metallic building materials, sells sand and gravel mixture in Moscow and the region.
Characteristics of ASG
The ratio of sand and gravel in a sand-gravel mixture is not the same.
- Natural ASG is a coarse material with impurities. No additional processing no mass is made after its extraction. This mixture is divided, depending on the place of extraction, into mountain-ravine, lake-river or sea. Natural ASG is used in land reclamation and road construction to add a drainage layer. The company supplies the natural mixture to customers in the form in which the raw materials were extracted from the quarry. The size of the pebbles in this mixture exceeds 5 mm in diameter, and their number in the total mass is no more than 10%.
- The enriched sand and gravel mixture is artificial material consisting of sand and granite chips given size. The quality of the material depends on this. Mixture varieties differ in the ratio of sand to gravel and the size of the pebbles. A popular brand of ASG is one in which the content of granite chips is 70% and sand - 30%.
Enriched ASG is divided into 5 types:
- Group 1 - from 15 to 25% gravel;
- Group 2 - from 25 to 35% gravel;
- Group 3 - from 35 to 50% gravel;
- Group 4 - from 50 to 65% gravel;
- Group 5 - from 65 to 75% gravel.
Application of PGS
Sand-gravel mixture is used when laying communication lines, when carrying out foundation work, when backfilling pits, as well as in construction and road laying. It is purchased for adding highways, drainage manifold gaskets and even sometimes for cooking mortars. True, the latter are made only using enriched ASG.
The Moscow region is very rich in deposits of this natural material. Its extraction here is well established, and therefore the cost of natural gas is low. It is difficult to find prices for PGS cheaper in the region than at Altair.
5 reasons to buy PGS from ISO Altair
- The ASG is delivered to the customer on the day of payment, since a sufficient number of dump trucks and loading and unloading equipment are provided for this. In addition, there is a stock of this material at the transshipment bases.
- The company sells only certified ASG.
- There is a system of discounts for regular and wholesale customers on an ongoing basis.
- The company's departments operate around the clock and seven days a week.
- ISO "Altair" offers the cheapest price for ASG in the region and accepts payment in a way convenient for the buyer.
