Which foundation is better for a house with high groundwater levels? How to build a house on “groundwater”? Some tips for a good owner Technology for constructing a slab foundation in groundwater.

They pose a rather great danger to any construction, especially if their level is high enough. In this case, you can begin work on the construction of not just any structure, but only one that is able to withstand the negative effects of moisture and carry out the correct distribution of all loads even on such unstable soil. It is mandatory to take measures to drain water and protect the structure from moisture.

A foundation with a high groundwater level must be designed carefully; either a pile type or a special monolithic floating foundation is suitable for construction. It all depends on other construction conditions, the size of the house itself, and the structure of the soil. To determine exactly what conditions are necessary, it is recommended to carry out such work only by a specialist.

Floating foundation

If too high is observed, then only a certain type of base must be used. Usually this is a monolithic foundation. To design a foundation, you must first order a special study, but in some cases you can determine the presence of a problem yourself. To do this, perform the following actions:

Before building the foundation, it is necessary to dig a hole and observe for some time the presence or absence of water in it.

To begin with, a hole is dug at the construction site, the depth of which is 3 m, and the side length is 1 m.
It is necessary to dig a test hole at the site of the future foundation, otherwise the actions will be ineffective.
The condition of the pit should be observed for some time. If it remains dry for a long time, then it means that you can safely begin work on this place. If water appears, the height of which is about 2 m, then this indicates the presence of a high groundwater level. It is recommended to contact a special company to conduct a study, determine the type of foundation, and the features of its structure.

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Materials for work

When the groundwater level is high, special requirements are placed on foundation materials. You can’t save money here, since waterproofing and corrosion protection must be at their best.

Specifically for the construction of a monolithic foundation with a high groundwater level, it is necessary to prepare the following tools and materials:

When building a foundation, a vibrating plate is needed to compact the cushion.

Equipment designed for digging a pit. An ordinary shovel is no longer suitable, although it also needs to be prepared. Usually, for foundation pits, they offer construction equipment for rent, which ensures digging of a hole of the required shape and depth in the shortest possible time. When performing such work, you need to remember some rules. The closer the groundwater is to the surface, the lower the height of the slab will be. It is impossible for its lower part to be in the water. This circumstance applies not only to concrete monolithic slabs, but also to blocks.
Gravel, sand, which will be needed to fill the bottom.
A special vibrating plate, which is necessary for compacting the cushion, especially if the soil is highly saturated with moisture and the groundwater level is high.
Polyethylene film for waterproofing. When calculating its quantity, it must be taken into account that it is laid with overlaps; part of the film will extend onto the walls of the pit.
Vapor barrier PVC membranes.
The choice of insulation must be carefully chosen, since not every material can be used. In this case, when the groundwater level is high, experts recommend using foam plastic boards that are not susceptible to the negative effects of moisture, practically do not absorb water, and do not change their properties even with constant contact with a humid environment. The cost of the material is not too high, and its installation is simple and quick.
Concrete mortar for pouring. You can use ingredients for mixing the solution in the form of cement, sand, gravel, water and other things, but experts recommend giving preference to ready-made dry mixtures. Today on sale you can find special formulations designed for high levels of ground water level. This does not mean that additional protection is no longer needed, but such solutions, after pouring and drying, resist aggressive environments much better.
To mix the solution, you need to use a concrete mixer; mixing concrete manually is problematic. You can make a concrete mixer yourself or rent it.
Special reinforcement and binding wire, which are necessary for reinforcing the foundation.
In some cases, it is necessary to use special concrete foundation blocks.

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Base diagram

If groundwater is close, then the foundation design will be slightly different. It is important to immediately determine exactly what type of base will be used. If the groundwater level is high, then the “pie” will be as follows:

Compacted soil layer; if necessary, additional work is carried out to strengthen it.
A cushion of sand and gravel, each layer is additionally compacted after wetting. The height of this layer is approximately 20-30 cm.
Monolithic concrete base, which is reinforced with steel rods.
Vapor barrier PVC membrane.
A layer of thermal insulation that allows you to create the necessary protection from the negative effects of moisture.
A special polyethylene film is used as a waterproofing layer.
Screed, i.e. a second layer of concrete pouring, to create the necessary “floating” base. When the soil moves, and this is possible if there is a high groundwater level, all loads will be distributed correctly, and cracks will no longer appear along the walls of the foundation and the house.

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Stages of creation

If the groundwater level is high, then it is best to build a monolithic slab foundation so that it can correctly distribute all the loads from the building. It is necessary to pour such a foundation carefully, strictly following all stages of work:

The first step is to dig a pit, the depth of which depends on how close the groundwater lies to the surface. This is determined as a result of a preliminary site survey. It is important to determine in advance the freezing point of the soil, soil structure and other indicators. Digging is carried out using special construction equipment. If water begins to seep through the walls, then it is necessary to take measures for drainage.
If groundwater lies close to the soil surface, then measures must be taken to strengthen the walls of the pit.
Sand and gravel cushions are placed at the bottom. Each layer is slightly moistened with water and then compacted. If groundwater is too close, a layer of geotextile must be laid at the bottom to protect the entire structure from water. In this case, the sand will not be washed out, the foundation will be well protected from all negative influences. The thickness of the filling, when the groundwater is high, is 20-30 cm. After compaction, each layer is topped up.
Pouring concrete can only begin after formwork and reinforcement have been completed. The formwork is made from edged wooden boards, they are fastened with galvanized nails. There should be no gaps left in the walls, otherwise the solution will begin to pour out. At any groundwater level, reinforcement must be provided. For this purpose, metal rods and binding wire are used. The number of belts is usually 2, the grid pitch is calculated individually. This stage cannot be ignored, otherwise the design will not be as reliable.

When building a foundation for a country house, it is worth taking into account many climatic and geological conditions: the proximity of groundwater to the ground level, the tendency of the soil to deform, etc.

If groundwater lies close to the surface of the earth and is above the freezing level, there is a considerable risk of basement flooding, subsidence and destruction of the entire building. To prevent this from happening, it is necessary to carry out drainage work on the site and choose the right foundation design for your home.

Groundwater accumulates in the upper layers of the soil as a result of saturation with precipitation or due to the proximity of water bodies. The seasonal accumulation of water in the upper layers of the soil should not be confused with permanent aquifers located at a considerable depth and supplying wells, springs and boreholes with water.

To determine at what depth the groundwater lies on the site, you can dig a hole at least three meters deep and protect it from precipitation. After the water level in the hole is established, determine the distance between it and the surface of the earth. If it is more than one meter, you do not have to worry about groundwater eroding the foundation and basement. If the water is close to the surface, you will have to take this into account when choosing a foundation design and carry out drainage work on the site.

What problems may arise during construction in areas with high groundwater levels:

flooding of the basement of the house;
loosening and destruction of concrete under the influence of salts dissolved in groundwater;
the appearance of fungus and mold in basements and basements due to constant dampness;
deformation and destruction of the foundation walls by frost heaving forces, the appearance of cracks in the walls of the house;
difficulties with landscaping the site, the inability to plant fruit trees;
the need for proper drainage work on the site.

Drainage work in areas with high groundwater levels

The purpose of drainage work is to lower groundwater. The simplest, but at the same time very expensive option is to increase the level of your site by at least half a meter. To do this, you will have to fill the area with dry sand or soil, and then level it with a bulldozer.

A more budget-friendly option is to create a network of reclamation ditches along the perimeter of the site. Due to the fact that soil is removed from the ditch, groundwater collects in the freed volume. Ditches can be made in the form of open trenches; it is advisable to reinforce their bottom with clay and crushed stone or line it with special gutters. It is also possible to create closed-type ditches, which are asbestos-cement pipes. Grooves or holes are drilled in their lower part through which water enters the pipe.

When designing ditches, it is important to take into account the terrain features of the site. If your house is located on a slope, the ditches must be oriented across the slope so that they are not washed away by powerful flows of water during floods and rainstorms. If your site is on a plain, it is necessary to ensure a slight slope of the ditch (no more than 5 centimeters of slope per 10 meters of length).

Outside the site, water should flow into a roadside ditch, and if there is none, into a drainage pipe. Ideally, the design of the drainage system of country and cottage villages should be carried out centrally, but if this does not happen, we recommend that you contact specialists.

Choosing a foundation design

Monolithic

A monolithic reinforced concrete foundation is a fairly reliable option for areas with close water levels in relation to the surface, as it ensures uniform load distribution over its entire area.

This design resists well the pressure of soil layers expanding during frost heaving.

To build such a foundation, you need to dig a pit, fill it with a layer of compacted sand, install reinforcing mesh and formwork, and then pour concrete. The surface of the concrete must be covered with plastic film to protect it from drying out and cracking, and the side walls of the foundation must be covered with waterproofing based on bitumen or roll materials.

The classic version of a monolithic slab foundation with bitumen waterproofing is suitable for areas with a short seasonal rise in water levels, and also allows you to build a basement. If the construction of a house is carried out in a swampy area or close to a pond, we recommend that you choose the option of a monolithic foundation on the so-called floating cushion.

Let's consider the main stages of construction of such a foundation.

The foundation pit should have a shallower depth than the level at which groundwater lies. This condition must be observed to ensure that the lower part of the monolithic slab is not in water.
Geotextiles or polyethylene are laid at the bottom of the pit. Impermeable material will prevent sand and gravel, which will be filled in in subsequent stages of construction, from mixing with the underlying soil.
The formwork is installed, and then a layer of sand at least 20 cm thick is poured. The pillow is watered with water to compact the sand; it is also advisable to use special devices (vibrating plates).
A layer of crushed stone or gravel of the same or greater thickness is poured onto the cushion, which will not allow groundwater to rise to the bottom of the foundation.
After compacting the sand and crushed stone cushions, it is necessary to cover their surface and the walls of the formwork with waterproofing material. This is necessary to ensure that water from the cement (the so-called cement milk) does not go into the ground.
A frame of reinforcement is mounted inside the formwork and concrete is poured. It is important to ensure that air cavities do not form in the thickness of the concrete; to do this, it is enough to pierce the concrete with the handle of a shovel. The concrete surface must be leveled with a shovel or construction vibrator. It is also extremely important to pour concrete in one step, and not layer by layer, which can reduce the strength of the structure. To do this, it is advisable to order a machine with concrete, rather than prepare it yourself in a concrete mixer.

This design is very reliable and allows you to build a basement or ground floor. Sometimes you have to carry out construction in conditions where there is already water in a freshly dug shallow pit. In this case, you will have to constantly pump it out with pumps or carry out proper drainage work on the site aimed at lowering the water level.

Columnar

Such a foundation resists soil deformation well when groundwater freezes. Holes are drilled in the ground, filled with a layer of sand and reinforced with metal mesh and rods.

The walls of the pits are covered with roofing felt or polyethylene, then concrete is poured, its surface is also covered with polyethylene to prevent drying out. Concrete blocks or pieces of asbestos-cement pipes filled with compacted sand concrete are laid on the frozen base. The disadvantage of this design is the impossibility of building a basement, as well as limited load-bearing capacity.

Pile

For many centuries, piles have been used to build houses in swampy or flooded areas. Good examples of this are St. Petersburg, Amsterdam and Venice. Piles are screwed or driven into the soil using special equipment. The best option is screw steel piles with a zinc anti-corrosion coating, which compact the ground during installation, which significantly increases the stability of the support.

Unfortunately, a pile foundation does not allow building a basement or ground floor of a house. In addition, piles cannot be driven or screwed into rocky soil, but in this case you are unlikely to face the problem of protection from groundwater.

To build a house with a basement on a site with groundwater lying close to the surface, we recommend choosing a monolithic foundation on a floating pad. This option costs a lot, but is very reliable and provides maximum protection of the basement from water. If your home does not require a basement or ground floor, you can choose a more economical pile construction, which is suitable even for marshy or flooded areas.

What to do with the foundation if groundwater is close? updated: February 26, 2018 by: zoomfund

The foundation is designed to receive and distribute the load from the house. Its further operation depends on the quality of the foundation of the house. The type of foundation depends on many factors, not least of which is the presence and level of groundwater.

Often there are soils with high groundwater levels, which significantly interfere with the installation of the foundation. It is completely impossible to build a foundation with a basement in such conditions due to the constant load. But making a foundation without a basement is quite possible even with a high groundwater level, provided that the installation technology is followed.

What effect does groundwater have?

The main substance of any foundation is concrete, which receives the harmful effects of groundwater, or rather those substances that are dissolved in them. Chemicals and salts loosen the foundation and cause it to delaminate. You can tell that the base is deteriorating by the appearance of plaque, a musty smell and stains.

In soils where the groundwater level is high, you will encounter difficulties when digging a pit, since water will flow into it, eroding the bottom and reducing the bearing capacity of the soil. That is why you first need to design a drainage system that will help drain water from the base.

Another negative effect of groundwater, but now not on the foundation, but on the soil itself, is suffusion. This term refers to the leaching of all mineral compounds from the soil. If this process is detected, you will have to engage in the process of draining the area, that is, perform water reduction

At high water levels, you can use pile foundation structures, which are more adapted to such conditions.

Groundwater level: definition and dependence on freezing level

To determine the groundwater level in the area selected for construction, it is best to trust professionals who will do it correctly and using technology. If this is not possible, then you can perform the determination yourself. In this case, the person who conducted the research will be responsible for the result. Work is carried out only in autumn or spring, since during these periods the groundwater level is highest. It is necessary to cover a pre-prepared hole with a depth of 3 meters and a width of 1 meter with polyethylene to protect it from precipitation and debris. After some time, a certain amount of groundwater will accumulate in this hole, the level of which needs to be measured. If it is less than 2 meters, then there is no need to carry out additional measures when arranging the foundation. Otherwise they will be needed.

The groundwater level indicator and the level of soil freezing express a relationship that reveals whether it is necessary to take into account the type of soil when installing the foundation. According to the requirements of SNiP, if the first indicator is less than the second, then there is no need to think about the type of soil, but you can calculate the foundation, referring only to the load from the structure itself.

If a house is being built on sandy, clayey soil or sandy loam with a high water level, then the foundation in any case is laid below the freezing level with the obligatory arrangement of a drainage system.

In addition, the groundwater level in such soils is usually increased by 0.5 - 1 m, judging by the practice of building foundations in these conditions.

Important! When carrying out work on arranging a drainage system, one should take into account the fact that the soil can settle significantly.

Foundation arrangement

To create a reliable foundation for a house, you need to choose the right type and design it. Let's consider the main types of foundations and the possibility of their installation on soil with a high groundwater level:

Performing drainage on the site

A drainage system is a mandatory element of arranging a foundation on soil with a high groundwater level. Usually, a pump is used to lower the water level in a pit or trench, but if during pumping springs appear at the bottom, then the pump is not a solution, since water will constantly flow and increase its level.

There are two ways to install a drainage system.

Open drainage. As a drainage system in this type of water drainage, drainage ditches with pipes are used through which water is discharged into the drainage ditch. Such a system will be more effective in areas located on slopes.
Closed drainage is a system of pipes and wells that are hidden underground and clearly designed in advance. To begin with, trenches are dug, the bottom of which is covered with sand and crushed stone.

Important! Before backfilling, the trenches are covered with geofabric, which will prevent silting of the ditch.

Drainage pipes are laid on top of the prepared base; this is usually done under the groundwater level. The entire structure is covered with sand and crushed stone and then covered with soil.

Where the drainage pipes make a turn, inspection wells must be installed. Their size is determined depending on the depth of the pipes.

Advice! If, after the work has been completed, water still remains on the site, then you cannot do without consulting a geologist.

Construction of a columnar foundation

Particularly popular on problematic soil with high groundwater is a columnar foundation, which will perfectly withstand the house in such conditions. The design of this base is the most budget-friendly, which in no way detracts from its dignity.

Such a foundation is made by installing piles around the perimeter of the future building and in those places where there will be load-bearing walls. The number of pillars is determined depending on the load that will be placed on the base. A sand-crushed stone cushion is placed in each well and reinforcement is made, after which concrete is poured. The piles are buried below the soil freezing level. This is done so that the foundation rests on solid soil, bypassing the problematic one.

Important! Before installing the piles, all water is pumped out of the wells to avoid problems with the solution hardening.

After installing all the piles, their upper parts are waterproofed, and a grillage is created, which is a strip that will become a support for the walls of the house.

Thanks to the columnar base, you don’t have to worry about soil heaving in winter. The cost of installation of piles will be significantly reduced if you use individual construction technology, which is the manual preparation of wells for piles.

However, despite its prevalence among private developers, the columnar foundation has some disadvantages. First of all, it is impossible to arrange a basement or ground floor in the house. If, however, a basement is planned, then its installation will significantly increase construction costs. The second disadvantage is that each pile must rest only on solid soil, and only a professional geologist can say at what depth it is. Sometimes it happens that there is basically no solid foundation on a site, even at depth. And lastly, a columnar foundation is not suitable for houses built from heavy building material.

Floating foundation device

It can even be installed in trenches and pits that are filled with water.

This foundation, when arranged in dry trenches and pits, is erected using the following technology:

Digging a trench with a depth of 80 cm and a width of 50 cm.
Laying geotextile on the bottom.
Erecting formwork in a trench to give the foundation a rectangular shape.
Construction of a twenty-centimeter sand cushion.
Filling gravel or crushed stone on top of the sand with a layer equal to or thicker than the layer of sand.
Compacting the created cushion and installing side waterproofing.
Installation of reinforced mesh with a rod diameter of 12 mm in the formwork.
Pouring the mortar into the formwork, which should be done only in one step.
After the concrete has completely hardened, the formwork is removed and the surface of the foundation is covered with a waterproofing mixture.

If the prepared trench or pit is filled with water, then drainage must be done, since water will not allow the concrete to harden and gain strength.

The drainage is a ditch with width and depth of 0.2 and 0.3 meters, respectively. Its installation has already been described earlier.

The rest of the work is no different from installing a floating foundation on dry soil and is carried out according to the previously described algorithm.

It is necessary to install a floating foundation clearly according to the scheme, so any deviation can lead to unpleasant consequences in the form of a poor-quality foundation, on which it will be very problematic to build a house and operate it.

How to protect the foundation from the harmful effects of groundwater

Any foundation must be protected from the destructive effects of groundwater. For this:

The main task of the foundation is to take the load from the house and distribute it evenly onto the ground. Therefore, when laying the foundation, it is necessary to take into account the type of soil and the location of the groundwater level (GWL). The last indicator may be too high, that is, the water is close to the soil surface.

Pouring a foundation under such conditions is difficult and costly. Therefore, the work contractor is faced with the question of what kind of foundation is needed for a private house if groundwater is close? This question affects not only the type of foundation structure, but also an additional choice that concerns the laying depth: below the groundwater level or above.

Groundwater influence

In the construction environment there is such a term - cement bacillus. This is when a concrete structure is destroyed under the influence of negative factors, which include groundwater. But we must understand that it is not the water itself that negatively affects concrete, but the salts and various chemicals dissolved in it. They penetrate into the concrete body, where they interact with cement or fillers, breaking their bonds with each other. Hence the appearance of all kinds of plaque, dark spots and unpleasant odors.

High groundwater level is a problem even at the stage of digging a pit. Water collects inside, which softens the bottom, which leads to a decrease in the bearing capacity of the soil. If this happens, you will first have to think through and install a drainage system, with the help of which it will be possible to pump out the water.

There are technologies that do not require drying the site. To lay the foundation, a pile method is used with driving pillars deep into the ground to dense layers. Not a bad option, but expensive and time-consuming. Without special equipment, such a foundation cannot be built. For private housing construction, this technology is rarely used. Therefore, the construction of a foundation with a high groundwater level is approached from the perspective of drainage.

And one more negative point. The dangerous time for such areas is winter with sub-zero temperatures. Freezing of the soil in winter turns into a dangerous situation for the foundation. Frost heaving and high groundwater level can destroy the foundation structure of a house in one season.

Determining the level

The groundwater level, that is, the indicator itself, is recorded in a geological organization, which has a branch in any large city. You can get information on the State Regulations there. Or you can measure the level yourself. To do this, you will have to dig a hole 3 m deep. Or drill a well to the same depth. A hole diameter of 20 cm will be normal, which will only require a garden drill.

Measurements should be taken in the spring, when the snow has melted. This is the period when the groundwater level is at its maximum peak point. Cover the hole with film to prevent precipitation from getting into it. And after a day you check how much water has accumulated in it. You can check with a pole: lower it all the way so that it touches the bottom. We pulled out and measured the dry area from the wet one to the mark that determines the ground level (the mark must be placed when measuring in the hole). This is the UGV.

If this indicator is more than 2 m, it means that in the area where the house is being built there is a moderate groundwater level. The foundation can be laid without additional measures.
If the length of the dry section is less than 2 m, then the water level is high. We will have to think through a water drainage system, construct it, and provide the foundation structure with protective materials.
It is the second position - with high groundwater - that will require the work manufacturer to select the type of foundation.

Soil freezing depth and groundwater level

The presence of high groundwater flow affects several positions related to foundation laying. They are clearly stated in SNiPs. And most often in the rules there is a relationship between groundwater level and the level of soil freezing. Because these two indicators are the main factors that reduce the strength of a concrete structure. Here are a few positions.

If the water level is less than the freezing level, then the foundation is calculated according to the usual scheme, that is, only for the load from the house.
If the soil at the construction site is weak, soft and mobile, then the foundation is laid below the UPG. In this case, a drainage system must be organized to drain groundwater.
If the groundwater level is very high, then it is not recommended to build a strip foundation.
If there is frequent flooding in the building area, then the only acceptable option is a house on stilts. In this case, the pillars are driven into the ground below its freezing level.

If the groundwater level is high enough and the area is drained, then there is a high probability of soil subsidence. This especially happens on sandy soils.

GWL closer than 0.5 m

In this situation, the only solution is piles. There are three options: ready-made monolithic, screw made from steel pipe and bored.

The ideal option is monolithic. They have been used in construction for a long time; they have increased load-bearing capacity and can easily withstand frost heaving. In addition, there is no need to think about soil drainage. True, this will require special equipment.
have become very popular today. In small private housing construction, such foundations for high groundwater are the optimal and cheap solution. Their only drawback is not the highest load-bearing capacity. Therefore, you will have to calculate the number of piles and the distance between them. It is recommended to install screw piles to a depth of no more than 3 m.
As for bored structures, this is a good option that has a high load-bearing capacity. But this technology also has its downside - a large amount of drainage measures will have to be carried out.

From 0.5 m or more

When choosing the type of foundation, preference should be given to the slab model. The thing is, if we are talking about a house, columnar structures in such a situation will not be able to provide the necessary load-bearing capacity of a large structure.

You can use it, but only a shallow one, which is usually built for small, lightweight buildings. In principle, it will withstand a frame cottage. In this case, it is recommended to build a foundation with an expanded base.

On the subject: When pouring it to a depth of up to half a meter, you need to understand that its thickness and method of reinforcement will depend on the number of floors of the building, as well as on the type of materials from which the walls will mainly be built. In this case, you will have to think about thermal insulation technology. By the way, this is an important stage in the construction of the slab.

Replacing the soil will help increase the load-bearing capacity of the slab. It is taken out to the groundwater level and instead filled with sand or crushed stone with careful compaction.

If the soil on the site is very weak, then the houses are filled with high groundwater until its materials displace excess moisture and stop sinking deeper.

1.5 m or more

Comparing the conditions described above, it should be noted that in this case it is possible to use strip and slab foundations on groundwater. But both structures must be shallow-depth.

Options for close proximity to groundwater

Options for foundations with close groundwater have already been given above. In principle, the slab structure in this case is the most commonly used structure. There is no need to build drainage ditches or think through protection methods, because everything is carried out using standard technology.

High groundwater - building a house without a basement

Everything here is quite simple if you use a surface or shallow slab as a base. That is, a house is being built without a basement and the walls rise immediately from the slab. Here is the sequence of work carried out:

A pit is dug up to the groundwater level;
A cushion of sand and crushed stone is filled with a tamper;
Waterproofing with roll material;
Installation of reinforced frame;
Pouring concrete.

If an insulated base is being constructed, then insulation is placed under the frame. In areas with high levels of subsoil water, this is an ideal foundation option.

Protection from high groundwater level

In the construction of foundations on such soils, three types are used, with the help of which it is necessary to protect the structure of the foundation and the house itself.

Coating, when bitumen mastics are applied to the foundation itself in several layers, due to which a smooth waterproof layer is formed on the surface of the structure.
Rolled, when the structure is covered with waterproofing films or membranes in several layers.
Plastering, when cement mixtures containing waterproofing additives are applied.

The thickness of the waterproofing layer is determined based on the occurrence of groundwater. The higher their level, the thicker the insulating coating.

Construction of a foundation on a floating cushion

What is a floating pillow? This is a thick layer of base made of several materials, which are separated from each other by insulating films. For high groundwater it is done very often. Here's the sequence:

Coarse sand is poured into the bottom of the pit or trench and compacted well.
Backfilling is done in layers with compaction of each layer. In this case, the final result is a layer 50 cm thick.
A waterproofing film is laid, preferably roofing felt.
Crushed stone is poured and compacted to a thickness of 30 cm.
Another layer of roll waterproofing.
Filling the screed with a thickness of 10 cm.

After which you can pour the monolithic reinforced concrete structure of the foundation itself. The pillow creates conditions under which the foundation can move relative to it. Such a foundation is often called a floating monolithic foundation.

Tape

The strip foundation on soils with high groundwater level is poured in exactly the same way as described in the previous sections. It is important to understand here that a strong base in the form of a tape is a large material cost. They mainly concern the consumption of concrete and reinforcement. At the same time, they try to construct the tape itself with an expanded sole.

If you try to save on something, the end result can lead to a weakening of the foundation structure, and, consequently, problems with the house itself will begin to arise. Therefore, one cannot deviate from the construction technology and the exact sequence of construction operations.

Pile type

As already mentioned, a pile foundation with a high groundwater level is the optimal solution. The main thing is to choose the right type of elements to be installed.

As practice shows, when constructing a large, heavy house, monolithic reinforced concrete pillars are used, which are manufactured at reinforced concrete factories.

This technology is called TISE. It’s true that this is not the cheapest technology of all piles, but it is the most reliable.

And although a screw foundation is cheaper, it does not provide the necessary load-bearing capacity for a heavy structure. It must be taken into account that waterproofing in a screw pile or other type of device is a mandatory measure.

Conclusion on the topic

So, the question of what kind of foundation to make if groundwater is close is very relevant today for many private developers. The article examined almost all the situations that they may encounter, and also recommended the types of foundation structures. In fact, it is important to understand that the choice itself is based not only on the types of soils and groundwater level.

It is important to first understand what kind of house will be built in an area with such a soil situation. If you are planning a large building made of bricks or blocks, you will have to allocate a decent budget for its construction. And you can’t save money here, because high groundwater level means moving, unstable layers that have weak bearing capacity.

In contact with

The main structure of any building is the foundation. It takes on and transfers its entire load to the ground. When choosing the type of foundation, the decisive factors are the characteristics of the soil, the depth of freezing, as well as the groundwater level (GWL), which causes many problems for the developer. Foundation construction at high groundwater levels greatly affects the strength of the foundation and load-bearing capacity of the building and requires large investments.

Why is groundwater dangerous?

They collect among the top layers of soil above a natural water barrier (usually clay). Their level is constantly changing, reaching peak values in spring or autumn. The following dangerous factors of high groundwater level can be identified.

Moisture, in contact with the foundation, destroys it and forms fungus and mold in the structures.
The foundation cannot retain moisture, and the basement and basement areas of the building fill with water.
If the groundwater level is high, you cannot simply fill the formwork with concrete. Pile technologies or prefabricated structures made of reinforced concrete blocks are needed, which increases costs.

Determining the groundwater level

For measurements, autumn or early spring is needed, before construction begins. You need to do the following:

First, a hole 3 m deep with a diameter of 1 m is dug and protected from precipitation.
After the water has collected, we measure the depth. If it is less than two meters, then there is no need to make allowances for groundwater when building the foundation.
If more, you need to choose a reliable foundation, protect it with a drainage system and waterproof the basement.

Soil freezing depth and groundwater level

The combination of these factors contributes to frost heaving of the soil, which often leads to destruction of the foundation. Therefore, the following must be taken into account:

When groundwater is below the freezing depth of the soil, the foundation is calculated only taking into account wall loads.
At high groundwater levels, the foundation is laid at depths exceeding the freezing level. At the same time, a drainage system is installed to remove moisture.
When designing, it is necessary to take into account that in places where drainage is installed, the soil may sag, so there must be a reserve depth (0.5 - 1 m)

Choosing a foundation design

If the groundwater level is high and constant, it is necessary to carry out global drainage of the area, build drainage ditches and waterproof the basement. Types of foundations with high groundwater levels you need to choose the one with the maximum area distribution.

Monolithic slab foundation

It is called a solid foundation, because it is a large flat reinforced concrete “pillow” on which the weight of the entire house is evenly distributed. When the soil moves in any direction, the slab does not lose stability. The disadvantage is the high cost.

The best option for areas with quicksand and increased groundwater level. Screw, reinforced concrete, rubble and other types of piles are used. They are driven into the ground or screwed until it stops in the hard layer. The ground part of the piles is united by beams into a rigid structure that can withstand heavy loads. Disadvantage: it is impossible to build basements.

This is a closed reinforced concrete strip that is poured under the load-bearing walls of the building. In private construction it is the most common supporting structure. For this type of foundation, a sand and gravel cushion is made to protect against groundwater. Use only when the water level is periodically increased in the presence of external waterproofing.

Construction of a foundation on a “floating” cushion

Such a foundation is considered the best option for foundation in houses with high groundwater level. Its device consists of the following stages:

First, a ring drainage system is installed.
Dig a trench or pit of appropriate size. The bottom is compacted using a vibrating plate. For slabs, a height of 40 cm is sufficient; the height of the tape above the soil surface is determined by builders based on specific conditions.
A “floating” cushion 50 cm thick is formed from compacted sand, gradually filling the trench layer by layer.
To prevent shallow soil from subsiding, geotextiles or other durable waterproof fabric are laid on top of the cushion.
Next, 15-20 cm of crushed stone is poured and compacted, and then roofing felt is laid.
Inside the trench or pit, formwork is installed from lumber, which is reinforced with bars that support the mounted panels.
Install reinforcing mesh. Monolithic slabs are reinforced with two rows of reinforcement (grade A-3, section 12 mm) and a cell size of 20/20 cm. Vertical rods are cut and fastened in a checkerboard pattern depending on the selected thickness of the slab, observing the following rule: the lower and upper meshes must recede from the bottom of the slab and the top of the formwork at a distance of 5-7 cm.
The foundation strip is reinforced with the same reinforcement. A frame is made of 4 rows of longitudinal rods connected to each other every 40 cm by transverse rods.

When pouring a monolithic slab, you need to use a mixer and finish the job within one day. During the maturing period of concrete, it is protected from erosion by rain and drying out. After removing the formwork, you need to coat the sides of the foundation with a waterproofing compound.

For elevated groundwater levels, installing a strong foundation can cost several times more than conventional foundations. Deviation from foundation construction standards and the use of cheap options will sooner or later lead to serious problems.