Which clay foundation is best for a house? How to choose a foundation on clay soil for a house made of timber Foundation on clay soil for a wooden house

Clay, loam, sandy loam are the main types of soils that individual developers have to deal with. In this article we will talk about building a foundation on loam, about the options for foundations and the subtleties of their choice. Naturally, we will mainly consider those foundations that you can build with your own hands, without resorting to the expensive services of builders.

What kind of 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. When dry, loams are usually crumbly - this property is provided by the sand filler. But when wet they become viscous - thanks to the clay. Due to the presence of a significant part of the latter, moistened loams freeze at subzero temperatures, increasing in volume. Therefore, special requirements are imposed on foundations on heaving soils (clay, sandy loam, loam). Based on specific construction conditions, individual developers rely on the following types of foundations:

reinforced slab. In this case, we are talking, as a rule, about a floating foundation laid above the HGT;
piles. Recessed below the GPG, they provide good stability of the building, but their use must 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 a foundation type

If you do not expect to share money with geological 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 (holes) to a depth below the GPG (approximately 30 cm). The meaning of the latter can be approximately determined from the figure from this article. Instead of pits, it is convenient to drill wells, for which you can use a regular garden drill. Already at the drilling (digging) stage, the nature of the soil, the uniformity of its occurrence, and changes in its composition with increasing depth are assessed. It is likely that a layer of clay will lie below the loam, and it will be necessary to build a foundation 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 laying a foundation, and the choice of the optimal type of foundation for a house depends on it. Already at the stage of geological exploration it will be clear whether they are below the GGT (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 is that it has a maximum base area, which means that even on loam with R about 1 kg/cm2 you 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 an impressive GGL. In winter, when the soil freezes, the foundation along with the house will rise, and when it warms up, 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 compression resistance characteristics than loam is found at shallow depths. It is relevant to lay such supports for small houses, log buildings, frame buildings, bathhouses, etc., when the load of the future structure makes it possible to economically justify the use of piles. This refers to the required quantity. In this regard, we recommend that you familiarize yourself with the information presented in this article.

Or maybe it’s still tape?

Often houses on loam are built on a strip foundation. You can build a shallow strip foundation (obvious savings), or a structure buried below the GPG. The last 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 strips in situations where geological exploration revealed that the soil layers lie evenly throughout the construction site. In such situations, you can count on the absence of serious uneven deformations during heaving.

Additional work

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

When the problem of soil moisture is solved, it would not be a bad idea 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.

Clay foundation, which one is better to use? This question arises before the developer when it is discovered that there is clay soil on his site. The strength of the foundation depends not only on the quality building materials. The reliability of the structure is greatly influenced by the characteristics of the soil on which the house rests.

Therefore, it is extremely important at the design stage to select the optimal foundation option that corresponds to the geological structure of the development site. This article will help private builders who are planning to build a house on clay: which would be better suited for such a case?

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

At particular risk are houses whose walls are built from lightweight building materials - foam blocks, for example (). Heaving forces in clays can only be balanced 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. Characterized by flowability and high plasticity. You can 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 or heavy. Loams are prone to frost heaving, so 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 groundwater. It is undesirable to build a foundation on sandy loam soils, but if there is no other choice, choose pile structures with a crushed stone base.

Choosing a foundation type

When building a foundation on clay soil, regardless of the type chosen, the main rule must be followed: the width of the base must be 25 percent or more greater than the upper part of the structure (). A cushion of sand and gravel (or crushed stone) is required.

Strip foundation

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

But if in the first case a recessed structure is being built, the base of which is below the freezing line, then in the second case preference should be given shallow foundation: on clay soil, the light above-ground part will not be able to counterbalance the heaving forces.

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

Only in this case, uneven deformations during soil heaving 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. During any movement of the soil, the slab 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 base of such a foundation has a maximum area, even a 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. Pile fields are arranged for large buildings: supports are installed in rows under walls, and in bushes under columns.

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

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

Piling scheme - screw foundation on clay soil.

Conclusion

Laying 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 wisely use the former, avoiding the latter.

Video about the dangers of clay for foundations.

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 used when building a house on clay:

Floating. A monolithic slab is constructed under the building, additionally reinforced with reinforced rods. 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 point that the use of such a foundation is not suitable for building a house in which a basement is planned.

Arranging 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

Soils on which the construction of a residential private house can be carried out can be divided into several different types. One of the most common ones are heaving soils, which are considered unfavorable for construction work. The fact is that its natural ability to retain moisture often leads to unpredictable pressure on the foundation, which can lead to deformation or even destruction of the entire structure.

But what to do if construction is only possible on this type of soil? You will have to not only take into account the characteristics of the soil, but also choose the right type of foundation. Of the soil characteristics on the site, you should pay attention to the following criteria:

a type of clay soil;
ground water level;
soil freezing depth;
weight, overall dimensions of the house, loads exerted by the structure;
presence of a basement.

Features of clay soil

To make a strong and reliable house on clay soil, you need to take into account the type of soil:

a mixture of clay, sand, small stone. This option is considered one of the best; it is a reliable base that is slightly susceptible to heaving and allows water to pass through well. Construction on such a site will be relatively simple, the structure itself will be durable and reliable;
sandstone, for which the clay content is up to 10%. Such a base is perfectly compacted under the influence of the load from the structure and conducts water well. The best option for construction is soil with coarse sand;
high clay content from 30%. It is already difficult to build a house on such soil, since the soil contains a large amount of water, which, when frozen, expands greatly, that is, swells. The soil begins to push out the foundation, breaks it, which causes problems with the structure of the house itself;
sandy loam and loam are mixtures of clay and sand. Their behavior depends on the composition; before starting construction, it is necessary to conduct a geological study to determine the possibility of building a house.

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What is the best foundation for clay soil?

Construction on clay soil is rarely carried out independently, as this is associated with numerous difficulties and costs. Therefore, most often they try to move the construction of a house to a more suitable site, but if there is no choice, then they turn to specialists.

For clay soils, two types of foundations can be used: strip and columnar, but the technologies for their construction differ from those adopted for ordinary soils.
They are not only more complex, but also more costly financially. What are the options for constructing strip and column foundations, which can be done specifically on clayey, rather complex, often water-saturated soils?

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Strip foundation on clay

You can make a strip foundation on clay soil. This is one of optimal options, but the cost in this case will be higher than when building on ordinary soil. To create a good, solid foundation belt type You can use one of three methods, including:

in the first case, after marking the territory, it is necessary to dig a trench under the base tape, at the bottom of which pour layers of sand and gravel cushion. Each layer should have a thickness of 15-20 cm. After backfilling, each time the material must be watered and compacted. Such a cake is poured to the soil level, after which buildings should be started from rubble stone or brick. The top of the base must be waterproofed using a material such as roofing felt, laid in two layers;

second version of the device strip foundation for clay soil it involves digging a trench for the future tape. But a backfill of sand and gravel should fill it only halfway. After this, the surface of the resulting pie is leveled, and the laying of one brick row. From edged boards formwork is made, which is impregnated with an antiseptic, dried, and then covered with a layer of tar. This formwork is poured with concrete to the required height of the foundation strip. It is best to make waterproofing on top from a material such as roofing felt;

according to the third option, it is carried out on dense, wet clay soils. Here a trench is also dug for the tape, after which formwork made of pieces of slate, which are overlapped, is lowered into it. The space that remains between the walls of the formwork and the foundation pit must be filled with sand. The filling is carried out to the middle, the remaining space is filled with gravel, which also needs to be compacted. After this, concrete can be poured in layers of 15 cm. Each layer is compacted until laitance appears on the surface.

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Columnar foundation on clay soil

A columnar foundation, especially its pile variety, is also excellent for construction on clay soil. This option will not be the cheapest, but its reliability is quite high, which is completely justified. In the selected area, it is necessary to drill holes with a diameter of 200-250 mm, the depth should be below the freezing point. A layer of gravel is poured onto the bottom, then lowered asbestos cement pipe, which is poured using concrete mortar compacted layer by layer. Such a foundation will need to be reinforced with metal rods. The installation step of support pillars should not exceed two meters; they are placed in the corners of the foundation, at the intersections of load-bearing walls.
To make a foundation, you need to prepare the following materials for work:

drill for wells with the required diameter;

asbestos cement pipes;

gravel for embankments;

reinforcing bars;

concrete for pouring.

There is another option for the base device. This is the so-called prefabricated backfill columnar foundation, which is the simplest and cheapest. A similar foundation is used in places where there are water-saturated soils, rather dense clay-type soils. The technology for construction is as follows:

the construction site is marked, after which the fertile soil layer is removed from it;

in the places where the supports will be placed, you need to dig holes in the clay, the depth of which will be 50 cm, the dimensions will be 40 by 60 cm. After this, a layer of simple coarse sand or a mixture of sand and gravel is poured onto the bottom of each well. This pillow is moistened and then compacted manually. The filling is done up to the ground level in layers;

Then the construction process continues by laying concrete blocks with dimensions of 20*30*50 cm on the cushions (you can also take blocks with dimensions of 30*30*50 cm). As a rule, the foundation requires the laying of two blocks, which are placed on top of each other. Bottom harness is treated with an antiseptic, the top is covered with a layer of roofing felt for waterproofing. The blocks are fastened together with cement mortar.

A foundation on clay soil can behave completely unpredictably, so before constructing it, you should conduct a qualitative analysis of the soil and choose the optimal type of foundation.

The presence of a clay component in the soil indicates that we are faced with heaving lands, due to the “capriciousness” of which, arranging the foundation can bring a lot of trouble and spend a significant amount of time.

Located near the surface, clay deposits instantly dissolve in melt water or under the influence of precipitation, losing their original shapes and exposing the base of the building’s supports.

Types of clay soils

Before determining the type of foundation, it is necessary to clearly understand what type of soil the construction will be carried out on.

Depending on the amount of clay content, soils are of the following types:

sandy loam is a loose rock containing sandy and silty components in combination with 5-10% clay;
loam - soil in which the clay component is represented in an amount of 10-25%, and the rest is sand;
clay is a fine-grained sedimentary rock with a high percentage of clay substance from 30%.

The main distinguishing characteristic of clay is its weakness to moisture, due to which it quickly turns into a dough-like mass and prevents further seepage of liquid into the soil. The layers of the studied rock can be located at a significant depth, which increases the risk of soil swelling in winter period due to freezing of stagnant water.

The optimal type of foundation and its features

On clay soils, you can make house foundations in any way. The use of one or another base depends on the individual characteristics of the site and the financial capabilities of the owner.

Regardless of what type of support is chosen, it is necessary in each case to carry out backfilling, which includes removing a 20-30 cm layer of soil below the intended location of the foundation and filling it with a layer of fine sand or crushed stone and thoroughly compacting it.

When choosing the optimal type of base, the following features must be taken into account:

the amount of clay in the soil;
freezing limit;
ground water level.

The determination of all of these parameters is carried out by conducting a qualitative soil analysis. If the groundwater horizon overlaps with the level of soil freezing, it is advisable to equip a primitive drainage system for water drainage.

Drainage is realized by digging trenches around the perimeter of the future placement of foundation elements. On clay soils, as a rule, the following types of foundations are installed:

tape;
pile;
shallow slab;
deep placement (in regions with extremely low temperatures).

Installation of strip base

When constructing structures on sandy loam and loamy soils, which are characterized by a low level of groundwater, a strip foundation is an ideal solution. The presented base is a reinforced concrete strip installed under all load-bearing structural elements. Arrangement of this type of house support allows you to subsequently create a basement and basement, as well as an underground garage.

Execution of work

The construction of a strip foundation for a house involves the following operations:

Transferring markings from a sketch to a section. Along the perimeter of the stretched signal ropes, it is necessary to make a pit with a depth exceeding the soil freezing level. In some areas with harsh climatic conditions, this figure can be from 1.5 to 2 m. The width of the pit is set based on the dimensions of the foundation with a margin of distance for the future placement of waterproofing, thermal insulation sheets and the facade layer, if they are implemented.
The bottom of the prepared pit is leveled and a gravel-sand mixture is sprinkled into a layer thickness of 15-20 cm, followed by compaction.
The walls of the pit are covered with waterproofing, which can be used as ordinary rolled roofing felt.
The bottom is filled with a 5-7 cm layer of concrete and a supporting substrate is formed (drying time from 10 to 15 days depending on the ambient temperature).
Installation of formwork with reinforced mesh placed inside the gutter.
We are pouring concrete. The pouring process is carried out in portions, 20-25 cm of concrete with its uniform distribution until completely filled.
After waiting for the hardening period, which usually takes about 3-4 weeks, we begin waterproofing work.

If the base is left to shrink over the winter concrete elements structures are covered with plastic film or any available means of protection.

Tape base is one of the most common types

The advantages of this method are:

uniform load distribution due to the large support area;
practicality and durability;
Possibility of equipping a basement or basement.

Flaws:

significant time and labor costs;
inflated cost of materials;
Possibility of implementation exclusively on sandy loam or loamy soils.

Slab technology

For clay soils, this option is also acceptable, since the total specific gravity of the entire house is evenly distributed over the slab support. In case of erosion or seasonal fluctuations of the soil, the entire foundation will be subject to displacement, and not its individual constituent elements.

Installation procedure:

As in the previous version, a 40-50 cm sand and gravel cushion is initially installed around the perimeter of the entire base. If groundwater is close to the ground, it is necessary to construct a drainage system with pipes sloping from the base.
A thin layer of concrete is poured and time is given for it to harden.
Formwork is formed, the inside of which is covered with a waterproofing layer.
Reinforced metal mesh is laid.
The final concreting of the base is carried out. It would be a good idea to add fine gravel to the solution during pouring.

To obtain a monolithic structure, concrete must be poured as quickly as possible.

Advantages:

resistance to shrinkage and seismic influences;
practicality;
resistance to soil erosion by melt and groundwater.

Flaws:

significant costs;
inability to equip basements and basements.

Watch the video on how to arrange slab base with your own hands.

Pile type foundation

Often applicable options for making a foundation on clay soil at home are: pile technology are pile-tape or pile-grillage type. In all respects, the presented methods are similar to the implementation columnar foundation made of brick.

During the calculations, the permissible load is determined for each pile. Depending on the depth of placement and the weight of the future building, the following types of piles are used in practice:

screw (by screwing in screw piles you can bypass clay layers of soil and build a foundation on harder rocks; the installation process is carried out both manually and through the use of special equipment);
bored (installed directly on the site of the house: a recess is dug or drilled, a sand cushion and a waterproofing layer are installed, asbestos pipes, inside which the reinforcing mesh is laid and filled with concrete);
driven (installed by using drilling machines).

For small houses, piles are placed along the perimeter of the load-bearing walls, and in the case of the construction of massive buildings, pile supports are mounted at the closest possible distances along the perimeter of the entire grillage part.

Subsequently, reinforced concrete beams or slabs are laid on the piles, which will evenly distribute the total weight of the structure onto each of the supports.

Advantages:

practicality and long service life;
resistance to significant loads;
relatively low financial costs;
quick installation;
possibility of repeated use of pile supports;
installation can be carried out in any natural conditions.

Flaws:

inability to equip the base and basement without additional excavation work;
the need to attract special equipment;
susceptibility of piled structural elements to corrosion processes.

Conclusion

In conclusion, I would like to highlight a number of key points that you should pay attention to when arranging the foundation of a house on clay soils, namely: the depth of the foundation on such types of soil depends on the freezing boundaries of the earth and groundwater, as well as specific gravity structures.

Even at the planning stage, you should not skimp on qualitative soil analysis, since subsequently an incorrectly erected support can lead to premature destruction of the entire structure, and the whole process will have to be repeated.