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A house starts with a foundation. The service life of the building and the safety of the inhabitants of the house depend on its quality. In order for the foundation of the house to be reliable, it is necessary, even before its construction, to purchase high-quality building materials, find out the composition of the soil, become familiar with the existing types of foundations, and find out which foundation is best to use on clay.

It is not so easy to build a foundation on clay soil, so it is necessary to prepare especially carefully for this process. Under the influence of the pressure of the mass of the building, the clay undergoes a compression process. This can continue for more than one year, and during this entire time the building gives rise to sediment, which can lead to deformation of the foundation and damage to the building. There are other “capricious” properties of clay that adversely affect the results of construction.

Types and characteristics of clay soils

In science, there are several bases for classifying soil. In one of them, the proportion of the presence of certain particles in it is taken as a basis. In nature, it does not happen that the soil consists only of clay or only of sand, or only of any other rock. There is always an impurity.

In this regard, several types of clay soil are distinguished.

• Clay. This type of soil contains at least 30% pure clay. To determine its amount in the soil composition, you can use this method - roll a “sausage” out of clay; if it does not lose its plasticity after some time, then the percentage of clay content can be considered high. When building a foundation on this type of soil, it is very important to know its freezing point; it should be above the groundwater level.
• Loam. The clay content ranges from 10 to 30%. A lump or “sausage” made of loam remains plastic only for a short time, then dries out and disintegrates into small particles. In turn, according to the quantitative presence of clay, this type of soil is also divided into types - light, medium and heavy.
• Sandy loam. The clay contained in the composition is between 5-10 percent. Areas with this type of soil are very susceptible to groundwater.

When constructing a foundation on clay soil, it is necessary to take into account which type of foundation lies within the construction area.

Considering the characteristics of clay rocks, you need to know that the clay itself, which is in their composition, varies not only in color (red, white, blue, gray, etc.), but also has very different properties. For example, glacial clay can withstand high loads only if it lies in a large layer. If it is located superficially, the soil is easily washed away by groundwater and melt water.

Near reservoirs in low-lying areas there are layers of alluvial clay. She is very flexible. Experts do not recommend building on areas with this type of soil. In case of emergency, you need to be more careful when choosing a foundation for construction.

How to choose a foundation

The construction of a foundation on clay begins with geological exploration work, during which the type of soil and methods of its occurrence are determined. It is important to identify the presence of groundwater and its location relative to the surface. It is necessary to determine to what depth the soil freezes. All these factors are decisive when choosing a foundation for a future building. The dimensions of the building and the material for laying the walls also need to be taken into account during preparatory activities.

Consideration of a shallow foundation design for a large building on clay soil must be approached with particular care. A strip foundation made in this way should be immediately eliminated.

One acceptable option is a floating foundation, which is a monolithic reinforced concrete slab. It can be ready-made or poured yourself. Possible movements of clay layers cannot cause harm to such a foundation, and, therefore, the entire building will be safe. The depth of the foundation slab depends on the size of the building being constructed. The main “disadvantage” of the project is its high cost.

On clay soil, a pile foundation is erected when groundwater is located close to the surface. This base option in this case will be optimal. Piles are driven or screwed (in the case of using steel structures with blades) to the depth where solid, immovable soil rocks lie, thereby ensuring the reliability of the structure. It is very important to correctly calculate the number of piles, their location under the building, and dimensions. Installation of piles can be done manually or mechanically. Columnar or pile foundations are not used in the construction of a building where the project provides for a basement.

“Tape” is another option for building foundations for clay soil. But it must be remembered that the depth of the foundation on clay in this case is very important. It cannot be less than the depth of soil freezing. Thus, it is necessary to take into account one more factor when choosing the type of foundation - the climatic conditions in which construction is carried out. What is certain is that the strip foundation for a building erected on clay soil must be buried.

Sometimes a combination of different types of foundation is possible. For example, a slab is laid under the main building, and a strip foundation is laid under those places where there is no heavy load (terraces, stairs, porches).

To answer the question of which foundation is best to use on clay, you need to take into account a lot of factors, so the question of choosing a foundation for construction is decided individually. It will be very useful to consult with professional builders or people who have extensive experience in such work before starting construction.

The strength of a clay foundation largely depends on what methods and techniques the builders use. There are some tips to help you avoid common mistakes.

• When laying the foundation, it is not recommended to save money that goes towards purchasing building materials. The highest quality modern materials are needed here.
• The bottom of the finished pit or trench must be cleaned by one of the methods - manual or mechanical. Manual leveling of the bottom is done with a shovel, and mechanical leveling is done with a mini-excavator with a leveling bucket installed on it. At this stage, the use of a laser level is mandatory.
• A “cushion” consisting of crushed stone, gravel and sand must be laid at the bottom of the pit under the foundation. Sometimes low-quality concrete is used. This is done with the aim of horizontally leveling the bottom surface and ensuring depreciation of the foundation.
• To reduce the soil pressure on the foundation and ensure its waterproofing, two layers of polyethylene film, roofing felt or other waterproofing material are laid on the bottom and walls of the trench.

• To give the foundation greater stability, the base is made wider than its upper part by approximately 25-30%.
• When pouring a strip foundation with concrete, tied reinforcement must be placed in the trench. Reinforcement in the foundation slab is made with two layers of mesh.
• The depth of the trench should not be less than the thickness of the fertile layer of soil; a recess from it of at least 50 cm is necessary.
• The finished trench is filled with formwork made of wood, sheet iron, laminated plywood or other material. After pouring and drying the mixture, the formwork structure is dismantled.
• The reinforced concrete mixture poured into the formwork is compacted (by vibration) to remove air bubbles and improve the properties of concrete.
• When building a foundation on clay, drainage and insulation work is not excluded.
• You can find out such an important indicator as the depth of soil freezing for different regions of Russia in a special summary table, which is available in the architectural department of any city; it is also published in specialized literature, on Internet sites, etc.

The foundation will become a reliable foundation for the entire building only if it is erected taking into account all the details and following technological processes.

Clay belongs to the category of heaving soils, thereforefoundation on clay soilcan behave quite capriciously. Clay is easily and quickly washed away by water, losing its original shape. Its plasticity depends on the composition of the soil, since different types of clay have different plasticity.

Being close to the surface, clay deposits are easily washed away by sediments and meltwater, exposing the foundations built on them. With increasing depth, the density of clay layers increases. However, the clay at depth remains constantly wet. A clay foundation for a house can behave unpredictably. Before building it, it is necessary to study the structure of the soil and decide on the type of foundation.

Types of clay soils

Depending on the proportion of pure clay in the composition of a particular soil, clay soil is called as follows:

• Clay is soil with a pure clay content of at least 30%.
• Loam - the portion of clay in such soil is about 10%.
• Sandy loam - the proportion of clay contained in the soil is between 5% and 10%.

Glacial and alluvial clay are also distinguished:

• Glacial clay has increased load-bearing capacity. It can withstand significant loads from a concrete foundation. But only if it lies deep enough. When lying at the top, it has increased plasticity.
• Alluvial clay can be found in lowlands, near bodies of water. Its high plastic properties make it necessary to refrain from constructing buildings on such soil. Under a foundation of this type, clay will quickly float, which can lead to the appearance of cracks on the walls of the building. In case of emergency, the construction of foundations is carried out on piles.

What kind of foundation to make on clay?

Clay is afraid of exposure to water. Before starting to lay the foundation, it is strongly recommended to carry out geological exploration. Its purpose should be to determine the homogeneity of the soil at the construction site. Often the soil on the site is extremely heterogeneous. The clay comes in layers, alternating with layers of sand. Therefore, the decision about which clay foundation is best to build must be made depending on the depth and composition of the clay layers.

This is done by drilling holes to the depth of the intended foundation.

If the composition of the soil is heterogeneous, then the best solution is to replace it with non-heaving soil. For example, crushed stone or sand. If the soil has a homogeneous composition, then its moisture content is examined. In the case of close groundwater, it is preferable to use a foundation on piles.

“There is clay soil on my site - which foundation will be the most reliable”? This question is asked by many land owners who are planning to build a house or some kind of building. So, the foundation may be different. It all depends on the specific composition of the soil, the location of the site and your capabilities.

Shallow foundation on clay soil

Clay soils pose a certain danger for laying shallow foundations. Conventional strip foundations cannot be laid in this way. Movements of clay as a result of heaving or erosion will not affect the walls of the building in any way. The slab can be poured independently using high-quality concrete.

You can also use a ready-made slab. The depth of the slab depends on the mass of the structure. It is prohibited to lay the slab on clay. Before laying begins, a pit is dug and gravel and sand are backfilled.

The only drawback of this method is the relatively high cost of the project.

Tape base

If you decide to build a strip foundation on clay soil, you should know: such a foundation must be buried.

The trench under it is dug to a depth that should exceed the freezing level of the soil. This figure will differ for different climatic zones. In the northern regions, sometimes it is necessary to dig a pit up to one and a half meters deep.

The bottom of the pit is first filled with gravel and then with a layer of sand. The deeper the pit, the greater the layer of sand that needs to be filled. The bottom of the trench (on top of the sand layer), as well as its walls, must be lined with polyethylene or roofing felt to ensure waterproofing of the foundation and reduce the impact of soil pressure forces on it.

The service life of the structure will depend on the choice and correct construction of the foundation. But even before these processes, it is worth conducting a detailed analysis of the area where construction will take place. It is especially important to have a complete understanding of soil characteristics. It is with these data in mind that the grounds can be calculated. Next we will talk about what a foundation can be like on clay soil, which one is better for building a house, and the features of clay soils will also be given.

To classify soil rocks, scientists analyze a combination of several factors, among which is the percentage of particles of a certain composition in the ground.

Certain types of soil consist of several impurities. For example, sand and clay. It does not happen that the earth in a certain place consists exclusively of one component (under natural conditions).

It is because of the different concentrations of impurities that clay soils are divided into:

• Clay. This type of soil contains more than 30% pure clay mass. Experts will make accurate calculations, but to determine it yourself, just take a little soil and roll it into a “sausage.” We can safely say that there is a large presence of clay in the soil if this “sausage”, even after a long time, succumbs to deformation and retains its plasticity. Before making a foundation in this case (and in others as well), you need to find out the depth of soil freezing, which should not reach the groundwater level.
• Loam. It is quite simple to understand that you will have to build a foundation on loam, using the previous method with a clay “sausage”. Only in this case will the plasticity disappear quickly and the soil will quickly dry out, which will be accompanied by the destruction of the “handmade product”. The percentage of clay in loamy soil is in the range of 10-30%.
• Sandy loam. The content of clay grains in this case is about 5-10%.

If sandy loam soil dominates at the construction site, then it is worth considering that it is significantly influenced by groundwater. That is why it is necessary to use moisture-resistant materials to create the foundation of the house, take care of the vapor barrier of the walls and protect the structure from subsidence.

It is worth considering not only the presence of pure clay in the soil, but also its characteristics. For example, a foundation on glacial clay will have the required safety margin only if the clay layer is wide enough (it will not be washed out by groundwater). Construction is also dangerous in the presence of soils that contain alluvial clay - its plasticity does not allow the required foundation strength to be achieved.

How to choose a base?

Geological surveys can accurately determine which foundation is best to choose for construction on clay soil. Specialists conduct an accurate analysis of soils, water depths, and freezing levels. Only by obtaining a complete picture of all factors can you choose the ideal foundation for a particular home, capable of supporting the weight of the structure and guaranteeing long-term service.

The main types of foundations that are used when building a house on clay:

• Floating. A monolithic slab is constructed under the building, additionally reinforced with reinforced rods. The reinforced concrete structure can be delivered from the manufacturer or made independently. Its feature is its stability in the presence of shifting soil layers. When choosing such a foundation, you need to correctly calculate the level of its deepening, and also take into account the fairly large cost of construction.
• Tape. Such a foundation on clay soil should be chosen with extreme caution. It is necessary to analyze the climatic conditions of the area and choose the right material for the construction, taking into account the characteristics of the soil. In any case, the foundation must be deeper than the level to which the soil freezes.
• Pile. This option is optimal (if not even the only reasonable one) in cases of groundwater concentration directly close to the earth’s surface. The use of driven or screwed supports allows you to reach those layers of soil whose density can provide reliable fixation of the structure. But it is worth considering the fact that the use of such a foundation is not suitable for the construction of a house in which a basement is planned.

When arranging a pile foundation, it is especially important to make the correct calculation of the number and method of arrangement of supports, and also to install them with perfect evenness.

Even an experienced specialist will not immediately answer which foundation would be better for constructing a building on clay - it would be wrong. As already mentioned, it is necessary to conduct a general analysis of the soil, the materials used, the climate of a certain region, the design features of the building, its size and much more.

What should you consider when building in an area with clay soil?

• Saving on foundation material can end in the most unfavorable way for the owner of the structure and its inhabitants.
• Be sure to build a cushion of sand, gravel and crushed stone or lean concrete under the foundation - it will improve the shock-absorbing qualities of the foundation, and will also allow the load to be transferred more evenly to the soil.
• For maximum stability of the base, it is constructed so that the lower part is approximately 30% larger than the upper part.
• After pouring the concrete solution, it is necessary to compact it. For this purpose, special vibration equipment is used. The impact of vibration helps remove air from the base structure, which has a positive effect on strength.
• Construction on a clay foundation does not eliminate the need for drainage and insulation work.

If you have problems determining the depth of soil freezing, you can contact the architectural department of any regional center - they should have such information.

A clay foundation for any structure, and especially for a house, must exactly correspond to the conditions of a specific construction and be completely constructed in full accordance with the design documentation.

Which clay foundation is best for a house? updated: February 26, 2018 by: zoomfund

The idea (initial) is normal. I’ve made such foundations myself many times, so I’ll give you a rough breakdown:
- we dig a foundation 600 mm from the expected zero mark;
- a cushion (or rather, a drainage layer) made of crushed stone, granite if possible, thick 200 mm, it won’t work less, it’s poured directly onto the bottom of the pit; if possible, a drainage pipe is made from the lower edge of the foundation (relative to the movement of groundwater across the site) with access to a drainage well;
-the first layer of waterproofing, maybe something simpler, for example, reinforced polyethylene. film placed on pre-leveled and compacted using available methods (for example, a manual tamper in the form of a log with a nailed handle, or a vibrating plate rented for the day, which is more technical) crushed stone; do not forget about a good overlap (at least 300 mm) when laying the film;
- sand pillow 300 mm(not less!);
- second layer of waterproofing (waterproofing with gluing of joints, rubber membrane, etc.);
- we knit a mesh from reinforcement: the lower one is 12 mm, the cell is 150x150 mm, we put it on linings made of thick bricks. 50 mm, or on special gadgets in the form of wheels put on reinforcement bars (IMHO, a waste of money, bricks work no worse)
the upper mesh is made of reinforcement, 10 mm in length, knitted in a cell of 150x150 mm, then raised by 170-180 mm relative to the first mesh and fixed with the help of knitting wire and pieces of reinforcement in length. 250-300 mm (don’t forget to put something under these “racks”, otherwise you will tear the waterproofing)
- the ends of the reinforcement cage, which, as it is easy to calculate, will “stick out” above the zero mark by 150 mm, are tied with a board of any thickness, to a height of about 200 mm, this will be the concrete pouring level (it is advisable to set the level of the top of this sheathing according to a level or water level .
- order concrete, grade M400, for fine granite crushed stone (it’s better to get it from a good concrete site), if you’re pouring now, ALWAYS ensure the presence of high-quality anti-frost additives (it’s best to buy a bag of potash and make the mixer driver pour it into the loaded concrete) and pour your pillow with a thickness of 300 mm (this is just enough for your home .
- after laying the concrete, especially now, in the cold, after setting, cover the entire surface with WET sawdust, a layer of 300-400 mm, in order to retain the heat generated by the concrete as it gains strength. From above everything is covered with ordinary plastic film.
- remove sawdust after 3 weeks; the foundation is ready.
I do not recommend casting a base with a stove. A waste of energy, formwork and unpredictability of the design. Lay it out of small-format concrete blocks, or cast it later.
Look at my topic in the "Best House Project" competition, on the second page, where I described how I did it.

The service life of all structures depends on the foundation. Its estimated cost is 30% of the total amount required for construction.

But the quality of the foundation directly depends on the soil - the place where the structure is erected.

Types of clay soil

Such soil varies in different places and according to its characteristics can be classified into 3 types: clay, loam and sandy loam. As a result, before the construction of a foundation on clay soil begins, the properties of the construction site are determined.

In the presence of clay, the composition of which is small particles up to 0.01 mm with admixtures of sand and dust, the foundation can be laid if the soil is homogeneous and its freezing level is above the layer of underground sources.

Clay soil is highly friable and plastic. The construction of the foundation in this case should be carried out by professional builders who have the skill and necessary knowledge.

In the presence of loam, sand and clay, the level of heaving of such soil is high. In this case, clay makes up no more than a third of the volume of the soil. The amount of clay affects the type of loam: light, medium and heavy.

Sandy loam comes with a clay content of no more than 10%. Due to the ability to move under the influence of ground sources, they are also called quicksand. It is not recommended to build on such a site. But due to the hopelessness of the situation, a pile foundation based on crushed stone will be used.

Only after determining the type of soil, groundwater levels and its freezing, a foundation is selected between two options: a strip foundation is suitable for homogeneous soil or a pile foundation if there are stones in the ground. The choice will also be influenced by the material from which the structure will be built.

When building a foam block or brick structure, a strip foundation is best suited to withstand the load placed on it.

If the loads exerted by a barn or greenhouse are insignificant, it is justified to erect a pile foundation, which will ensure the monumentality of such a structure.

Despite the design of different buildings, the soil will be the same. In order to save money, it is possible to use sawdust or sand as substitutes for gravel or crushed stone. But clay is an insidious substance and requires compliance with all building rules and regulations.

Regardless of which foundation is best built on clay, there is always the possibility of it breaking, swelling and subsidence. The reasons for this may be insufficient depth of the foundation, or a lot of pressure on it.

To avoid the pressure of freezing soil, it is recommended to treat the base with machine oil or cover it with PVC film, which will not allow water to pass through during a thaw. The top soil layer must be insulated with expanded clay or crushed stone.

Selection Dependency Factors

On clay it is possible to build a slab or strip base, on pillars or piles. It all depends on the following factors:

Price. In terms of stability and reliability, as well as price, the slab foundation is the leader. It is ideal for heavy buildings.

But if there is a basement, a recessed strip foundation is more expensive than a slab foundation. Pile and columnar foundations are excluded for buildings with a basement on clay; such foundations are suitable for light buildings without basements. At the same time, on stilts is the best and inexpensive solution.

Uniform or interspersed arrangement of clay layers. The site is surveyed by drilling wells to the depth of soil freezing. With different soil compositions in different places, the base is covered with crushed stone and sand. When installing the base on piles, it must be brought to a dense clay layer.

In case of severe heaving of the soil, the determining factor is the weight of the structure. For high loads and large sole areas, reinforced slabs are preferred. For light loads, a strip or pile-grillage base is suitable.

Depth of underground sources. Clay is a natural waterproofing agent, but at depth it is constantly wet. If the foundation is deep, the choice falls on a monolithic foundation or on piles. The tape type is excluded.

Soil freezing depth. The complexity and cost of construction depend on the depth of water and freezing. A foundation on piles for an uneven site is an opportunity to reduce costs, labor intensity and increase reliability. Piles are preferable for complex soils where clay and stone are mixed.

Leveling out the shortcomings of clay soil and using its advantages to strengthen the structure depends on the correct choice of foundation.

Construction process. As an example, we will describe the creation of a foundation on clay soil for a timber bathhouse:

• Marking for the base;
• Digging a trench 1.5 m below the fertile layer and 3 times wider than the intended base;
• Installation of metal or wooden formwork;
• Making cement and pouring it into formwork, followed by compacting it;
• Time for cement to dry and formwork to be dismantled;
• Heat treatment of the foundation using firing;
• Backfilling the trench after the firewood has completely burned out.

Despite the disadvantages of clay soil, it has a number of advantages. Such a foundation can withstand heavy loads with deep underground sources. As a result, the supporting structure is reliable and can serve as an example of savings.

If the soil is shallow, preference is given to a foundation on piles, which will be more expensive, but it is not inferior in reliability and quality.

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