Is it possible to make a columnar foundation on clay. What is the best foundation for clay soil? Soil features and base selection

Clay soil in your area, despite its complexity, can serve as a good basis for building foundations and buildings.

Features of clay soil during the construction of the foundation

Clay soil consists of tiny flakes, between which moisture can accumulate well. This leads to the fact that such soil acquires the property of "heaving" - it solidly increases the volume when the moisture in it begins to freeze. This property must be taken into account when building a foundation on clay soil. Due to the fact that clay soil can displace the foundation in the cold season, the space around the foundation on your site will have to be covered with sand. Such backfilling will lead to some increase in the cost of construction.

Assessment of the state of the soil on the site

Before starting to draw up a foundation project, it is necessary to carry out survey work on your site.

The soil condition check consists of the following components:

• Evaluation of soil quality at various horizons,
• Checking the level of groundwater,
• Calculation of the level of soil freezing.

In order to conduct a comprehensive check of the state of the soil, it is necessary in the spring, during a high level of standing groundwater, to drill a pit about 2.5 meters deep at the site of the future structure. The soil raised from various horizons of the pit will give you a complete picture of the structure and moisture content of the soil. The depth of soil freezing is calculated based on the maximum winter temperatures for previous periods and the actual characteristics of the soil, like clay, for example, freezes to a level different from sandy soil.

Carrying out drainage work

In the event that a high level of groundwater is recorded on your site, and even more so if it exceeds the level of soil freezing, it is necessary to carry out drainage work before building the foundation. The construction of the drainage system includes the formation of trenches with pebble backfill around the future building, which will divert water away from the building. The drainage system can also be made in the form of pipes with holes, which are located underground and have a slope, which also helps to drain water.

Drainage system on site

Types of foundations on clay soils

Depending on the characteristics of clay soils in your area, the degree of clay, sand and water content in them, professional builders recommend forming the following types of foundation structures for future buildings:

• Strip foundation
• pile foundation
• Combined strip-pile foundation

Each of them has some nuances in construction. Consider how to build such foundations with your own hands.

We build a strip foundation on clay soil

The strip foundation is a concrete monolith, which rests on the ground with a large area of ​​\u200b\u200bits base. The concrete tape of such a foundation should be located under all load-bearing walls, regardless of whether they are external or internal.

The construction of this foundation is quite labor-intensive, but, nevertheless, such a strip foundation on clay soil can withstand the weight of a large, solid structure.

After drafting the strip foundation, it must be transferred to the area. Before that, it is better to remove a layer of fertile soil from the construction site, as it can be profitably used in other parts of your "estate".

Marking for the construction of a strip foundation (as well as any other) is made using pegs and stretched cords. When constructing a rectangle, not only its sides, but also its diagonals are measured with a construction tape measure. Thus, the construction of ideal right angles is achieved.

We build a columnar foundation on clay soil

On clay soil, it is also possible to build a columnar foundation. To do this, you can use both ready-made supports (reinforced concrete pillars or screw piles), and form bored piles.

Screw supports - made of durable metal pipes can be screwed into the ground with simple mechanical gates, but to place reinforced concrete piles, you will have to use the services of construction equipment.

With your own hands, you can form bored piles. To do this, large-diameter wells are drilled at selected locations (at all corners of the building, at the junction of internal load-bearing walls and at least every 2.5 meters in a straight line). A sand and gravel cushion is laid on their bottom and a 10-centimeter concrete support is poured. Pipes (made of polymers, asbestos cement or metal) are placed in the wells. A multi-tiered metal reinforcing structure is formed inside the pipes, which is then poured with concrete mortar.

Clay foundation, which one is better to use? Such a question arises before the developer when it is discovered that clay soil is on his site. The strength of the foundation depends not only on the quality of building materials. The characteristics of the soil on which the house rests have a great influence on the reliability of the structure.

Therefore, it is extremely important at the design stage to choose the best option for the foundation, corresponding to the geological structure of the building site. This article will help private builders who are going to build a house on clay: which one is best for this case?

The main problems in the construction of a foundation on clay soils are the likelihood of subsidence, breaking off and swelling of the foundation of the building. This can happen under the influence of too much pressure on the foundation, or due to insufficient depth of its foundation.

In the zone of particular risk are houses whose walls are built of lightweight building materials - foam blocks, for example (). Heaving forces in clays can be balanced only by a heavy above-ground part - brick, stone or reinforced concrete.

Types of clay soils

Clay soils include:

• sandy loam;
• loams;
• clay.

Clay is a collection of small (up to 0.01 mm) particles with a small admixture of sand and dust. It is characterized by flowability and high plasticity. It is possible to build on clay if the soil is homogeneous and the groundwater is deep. But in any case, such a case is not at all suitable for independent construction.

Loam contains up to 10% clay. Depending on its specific volume, the soil can be light, medium and heavy. Loams are prone to frost heaving, so the construction conditions on them are classified as difficult.

Sandy loam contains no more than 5 percent clay. These soils have another name - quicksand, as they have great mobility under the influence of groundwater. It is undesirable to build a foundation on sandy loamy soils, but if there is no other way out, pile structures with a crushed stone base are chosen.

Choosing the type of foundation

When building a foundation on clay soil, regardless of the type chosen, the main rule must be followed: the width of the sole must be 25 percent or more greater than the upper part of the structure (). Without fail, a pillow of sand and gravel (or crushed stone) is equipped.

Strip foundation

A strip foundation on clay is suitable for heavy buildings and light wooden buildings ().

But if in the first case a buried structure is built, the sole of which is below the freezing limit, then in the second case, preference should be given to a shallow foundation: on clay soil, the light above-ground part cannot become a counterweight to heaving forces.

Monolithic tape is used only if the groundwater is below the freezing line of the soil. On loamy soils, this type of foundation can be built if geological exploration has confirmed the uniform occurrence of the layers throughout the construction site.

Only in this case, uneven deformations during heaving of the soil will not threaten the structure.

slab foundation

Slab foundations on clay are the most reliable, but also the most expensive). Therefore, they are practiced only in the case of the construction of luxurious mansions.

Another name for this type of foundation on clay soil is floating. With any movement of the soil, the plate moves with it, maintaining the uniformity of the load.

The slab is poured almost on the surface of the earth. But buried slabs are also practiced - in houses with basements. In this case, the walls of the underground part of the house and the slab form a single monolithic structure.

If you need to build a foundation on loam, there is no better solution than a monolithic slab (). Since the sole of such a base has a maximum area, even the calculated soil resistance of 1 kg / cm2 is sufficient to ensure the stability of the structure.

Pile foundations

With the help of piles, a foundation is built on sandy loam and other types of clay soils. Under the buildings of a large area, pile fields are arranged: supports are installed under the walls in the form of rows, and under the columns - bushes.

When choosing the type of foundation on clay soil with a high level of groundwater, the most right decision is the construction of a house on piles (). In this case, it is necessary to adhere to the basic rule - the support must be carried out with broadening downwards.

Screw piles have proven themselves well - structures equipped with screw blades in their lower part). When the screw is screwed in, the density of the soil around the support is maintained - the blades do not loosen the soil, but cut individual layers. The estimated installation depth of the screw is below the aquifer and the freezing point.

Scheme of a pile-screw foundation on clay soil.

Conclusion

Building a foundation on clay soils is a difficult task, but quite feasible. The main thing is to know all the advantages and disadvantages of such soils and correctly use the first, avoiding the second.

Video about how dangerous clay is for the foundation.

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

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

Types of clay soils

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

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

Also distinguish between glacial and alluvial clay:

• Glacial clay has an increased bearing capacity. It can withstand significant loads from a concrete foundation. But only if it is deep enough. At the top occurrence, it has increased plasticity.
• Alluvial clay can be found in the lowlands, not far from water bodies. Its high plastic properties make it necessary to refrain from building buildings on such soil. Clay of this type will quickly float under the foundation, which can lead to 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 do on clay?

Clay is afraid of water. It is highly recommended to carry out a geological survey before starting the laying of the foundation. Its purpose should be to determine the homogeneity of the soil at the construction site. Often the soil on the site is extremely heterogeneous. Clay goes in layers, alternating with layers of sand. Therefore, the decision on which foundation to build on clay should be made depending on the depth and composition of the clay layers. This is done by drilling pits to the depth of the proposed foundation.

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

“I have clay soil on my site - what foundation will be the most reliable”? This question is asked by many owners of plots who are going to build a house or some kind of building. So, the foundation can 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.

But a reinforced concrete slab is just right for clay soil. There will be a so-called floating foundation. Clay movements as a result of heaving or erosion will not affect the walls of the building in any way. The slab can be poured independently, from high quality concrete.

You can also use a ready-made plate. The depth of the slab depends on the mass of the structure. It is forbidden to lay the slab on clay. Before starting the laying, a pit is dug out, gravel and sand backfilling is performed.

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 that such a foundation must be deepened.

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

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

If the construction site is located on clay soil, it is necessary to familiarize yourself with the nuances of the soil masses and their characteristics. For this, a preliminary analysis of the soil, its bearing capacity, the depth of the aquifer, the freezing point, and so on, is carried out. But it is worth considering the types of clay soil, so that the construction of the foundation of the house is not too expensive.

Soil types

To determine “clay”, the soil must contain at least 30% of this material, loam is 10% clay, and sandy loam contains 5-10% clay. There are types of glacial and alluvial clay. Glacial is characterized by a very high density and excellent bearing capacity, which is revealed only in deep layers. Alluvial clay is a plastic soil, so it is better to completely abandon construction work on such a site or equip the structure on piles.

The nuances of foundation construction technologies, types of foundations

Starting the construction of the foundation of a house on clay, it is important to remember that the soil does not tolerate water, so it is important to conduct geological surveys. For example, maybe in your case, clay layers alternate with sand ones, and you will also have to take into account the depth of each layer. By doing the work yourself, you can determine this fact by digging pits, the depth of which depends on how deep the type of foundation being built will be.

Important! While maintaining the heterogeneity of the soil, it is better to use crushed stone or sand backfill, taking into account the moisture content of the layers. And with a high level of groundwater outlet, it is better to give preference to a pile foundation.

Shallow foundation on clay soils

The design makes you think because of the low bearing capacity and low strength of clay soil. To avoid the danger of cracking and warping of the foundation of the house, it is better to use a reinforced concrete slab, ideal for this type of soil composition.

A floating foundation is also allowed, the strength of which does not depend on the intensity of soil erosion. The slab is poured independently using concrete of especially strong grades. But you can take a finished slab, additionally reinforced. The depth of the bookmark will depend on the weight of the house. And for the installation of the slab, you will need a pit with a cushion of gravel and sand.

Advice! The high price of the project is considered a disadvantage of arranging such a foundation.

Strip foundation

Only deep strip foundation is allowed. Construction begins with digging a trench deep above the freezing point. Then the bottom is covered with gravel, sand and it is important to take into account the depth of the trench in order to equip the correct thickness of the pillow. After that, a layer of insulating material (polyethylene) is laid over the sand, which reduces the pressure force of the weight of the house on the foundation on clay soil. When arranging the strip base, before pouring the concrete composition into the trench, it is necessary to mount the reinforcement connected to each other.

Advice! The arrangement of the tape base is justified in cases where it is necessary to have a basement of a house built on heterogeneous soils. And if the construction is carried out on heaving soils, it is worth giving preference to the foundation on a monolithic slab or piles.

Advantages of a tape base on clay:

1. The possibility of arranging a basement or basement;
2. High structural strength;
3. Long service life without loss of quality characteristics;
4. Providing a solid foundation for the building.

• High cost of work;
• The need to consume a large amount of material;
• Labor intensity.

Pile foundation on clay

This type of base is considered especially popular due to the provision of sufficient strength and stability of the entire structure. At the same time, the type of pile supports is large, which allows you to choose the most suitable elements for homogeneous clay and heterogeneous soils.

Important! When deepening piles, it is necessary to achieve dense layers that are not subject to freezing, displacement due to filling with aquifers. The immobility of these layers will protect the base, and, consequently, the structure, from all destructive factors.

Experts recommend building a pile foundation on clay using driven or screw piles, choosing from which type is more economical and practical. But in some cases, bored piles for a house are acceptable, the installation of which requires drilling holes, pumping out water, reinforcing and concreting. At increased costs, this method guarantees exceptional strength of the base.

Pile foundation advantages:

1. Increased strength over a long period;
2. Endurance of big weight loadings;
3. Ideal for unstable ground masses.

Disadvantages:

1. The threat of susceptibility to corrosion (the treatment of piles with special compounds will help to minimize the threat);
2. The need for additional costs;
3. The absence of a basement, or the mandatory carrying out of labor-intensive and costly work.

Pillar base on clay

If you plan to build a wooden house without a basement on clay, this option is better than any other. Therefore, choosing what kind of foundation will be, it is worth paying attention to the least expensive way of arranging the foundation. The technology is simple, you need to dig the pillars in increments of at least 1 meter, and the base can be made of pre-fired piles made of oak or pine wood. Holes for piles cannot be higher than the freezing point of soils, but must fall at least 2 meters below.

Advantages of column bases:

• Affordable price;
• Efficiency of installation and the possibility of doing work with your own hands;
• The use of a small amount and range of materials.

• Short service life;
• Low bearing capacity, for buildings of large mass it is better to choose a different base;
• Cannot be used on moving ground.

Considering all the features, you can always choose which foundation is more suitable for arranging on a construction site in terms of strength, economy and speed of construction. However, considering these factors, one cannot ignore the mass of the building, the water content of the soil, the number of storeys of the building and other characteristics that affect the operation and longevity of the house.

Clay, loam, sandy loam are the main types of soil that individual developers have to deal with. In this article we will talk about the construction of a foundation on loam, about the options for bases and the intricacies of their choice. Naturally, we will mainly consider those foundations that can be built with our own hands, without resorting to the expensive services of builders.

What foundation to build on loam

Loamy soil is a mixture of clay and sand, in which clay predominates. The percentage of components can be different, hence the different properties of loam. For example, the more sand it contains, the greater the porosity coefficient and the lower the calculated soil resistance. In a dry state, loams are usually crumbly - this property is provided by sand filler. But in the wet they become viscous - the merit of clay. Due to the presence of a significant part of the latter, moistened loams freeze at low temperatures, increasing in volume. Therefore, special requirements are imposed on foundations on heaving soils (clay, sandy loam, loam). Based on the specific construction conditions, individual developers rely on the following types of foundations:

• reinforced plate. In this case, we are talking, as a rule, about a floating foundation laid above the GIP;
• piles. Buried below the GPG, they provide good stability of the building, however, their use should be justified by operational and economic factors;
• strip foundation. On heaving soils, a rigid reinforced tape is erected either above the GPG (for light buildings and subject to drainage and insulation of the foundation), or below - a house with a basement is obtained

Before choosing the type of foundation

If you do not expect to share money with exploration specialists, then you will have to analyze the soil yourself. To do this, at the proposed construction site, it is necessary to dig several pits (pits) to a depth below the GPG (approximately 30 cm). The value of the latter can be approximately found in the figure from this article. Instead of pits, it is convenient to drill wells, for which you can use an ordinary garden drill. Already at the stage of drilling (digging), the nature of the soil, the uniformity of its occurrence, changes in its composition with increasing depth are assessed. It is likely that a layer of clay will lie below the loam, and the foundation will have to be built on clay.

It is worth noting that such exploration work is recommended to be carried out in the spring, when the groundwater level is closest to the surface. Groundwater can cause unnecessary trouble when building a foundation, and the choice of the optimal type of foundation for a house also depends on them. Already at the stage of geological exploration, it will be clear whether they are below the GIP (ideal case) or above (you will have to resort to additional work, which will be discussed below).

slab foundation

A slab is one of the most reliable types of foundation. Its main advantage lies in the fact that it has the maximum sole area, which means that even on loam with an R of about 1 kg / cm 2, one can count on the absence of problems with the stability and shrinkage of the structure. At the same time, a slab foundation can be erected even with a high groundwater level and with an impressive GWP. In winter, when the soil freezes, the foundation together with the house will rise, and when it gets warmer, it will fall. That is why it is also called a "floating" foundation.

pile foundation

Pile foundations are erected in cases where soil with better compressive strength characteristics than loam is found at a shallow depth. The laying of such supports is relevant for small houses, log cabins, frame buildings, baths, etc., when the load of the future structure makes it possible to economically justify the use of piles. This refers to the required number of them. In this regard, we recommend that you familiarize yourself with the information provided in this article.

Or maybe a tape?

Often houses on loam are built on a strip foundation. It is possible to build a shallow strip foundation (obvious savings), or a structure buried below the GPG. The latter option is most often chosen when building a house with a basement. It is the most material-intensive and therefore not the cheapest. In general, it is advisable to build reinforced concrete belts in situations where, during geological exploration, it turned out that the soil layers lie evenly throughout the construction site. In such situations, one can count on the absence of serious uneven deformations during heaving.

Additional work

The main problem in building a house on heaving soils (including loams) is to build a foundation that adequately perceives the increase in soil volume in the cold season. The reason why all this happens is soil moisture. Therefore, with a high level of ground and surface water, it is necessary to arrange foundation drainage. It is best to think about this issue even at the foundation construction stage - this way the costs will be less, and the efficiency of the drainage system will be much higher.

When the problem of soil moisture is solved, it will not be superfluous to provide additional thermal insulation around the perimeter of the house. This is done in order to reduce the depth of soil freezing, thereby reducing the risk of soil heaving to zero.