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The effect of water on a concrete foundation. Options for building a foundation on clay soils with high groundwater levels. Monolithic slab and pile foundation

Groundwater is underground layers of water in the first (upper) layer from the surface of the earth, which is formed due to atmospheric precipitation, the amount of which directly depends on the season. This level is highest in the spring, when the snow begins to melt, or in the fall, due to the abundance of rain.

To build a reliable house, it is necessary to protect the structure from the influence of groundwater on the foundation.

Groundwater affects the structure of the foundation and the physical condition of the soil around it:

• due to the varied chemical composition found in water, the foundation is constantly susceptible to destruction;
• clay, earth, sand are washed away, which leads to constant subsidence of the building;
• mold, various fungi, a damp smell, white or yellowish salt stains appear.

We build a foundation with a high groundwater level

To start construction on a site with a high groundwater level, you need to properly design the foundation.

When designing a foundation, it is necessary to take into account not only the groundwater level, but also the depth of soil freezing.

Let's figure out what type of foundation is suitable for soil with a high groundwater level:

1. Slab foundation. It does not need to be buried deep in the ground; soil expansion in winter does not affect it. Disadvantage of a slab foundation: if the foundation is not isolated from water, it will gradually wash out a hole in the foundation and it will crack. To prevent this from happening, the slab foundation must not only be placed on a bed of crushed stone and sand, but also isolated from the ground. Ruberoid is perfect for this.
2. Brick foundation. When designing, waterproofing must be taken into account. Thanks to the design of the brick foundation, the expansion of the soil in winter will not affect it. And if you make a good blind area, then even external water will not threaten the house. The disadvantage of this type of foundation: a brick foundation requires a lot of costs for its construction.
3. Columnar foundation. Even if you lay it below the freezing depth of the soil, its cost will be cheaper than other types of foundation. The disadvantage of a columnar foundation is that it is not suitable for heavy buildings.
4. Shallow foundation strip foundation. It is also called floating foundation. Suitable for buildings made of heavy materials.

High groundwater - we build a house without a basement

It is not recommended to build a basement in an area with a high groundwater level. Groundwater will flood the basement and contribute to the destruction of the foundation and the structure as a whole.

If you planned to have a small basement, then it is better to build it separately from the house, insulate it and waterproof it, and build an earthen mound in the form of a hill on top. Such a basement will serve well and for a long time; it will always be dark, dry and cool.

So, when we have figured out everything with the basement, we can move on to laying the foundation. If your house is lightweight, for example, made of wood, you can lay a columnar foundation, since it is best suited for construction on an area with a high groundwater level. However, if the house is too heavy (brick, for example), then a floating foundation would be the best choice.

Floating foundation for areas with high groundwater levels

A floating foundation can be built both in dry trenches and pits, and in trenches that will be filled with groundwater.

Floating foundation in dry pits and trenches

1. It is necessary to dig a trench 80 cm deep and 50 cm wide. At the bottom you need to put material that will prevent the bedding from moving with the soil if water washes it away. For this, it is best to use geotextiles. In order to give a rectangular shape to the concrete, we erect formwork in the trench.

2. Construction of a sand cushion 20 cm thick. Gravel or crushed stone should be poured on top of this cushion. The thickness of the crushed stone layer should be equal to the thickness of the sand cushion or be thicker. For example, with a sand cushion thickness of 20 cm, the thickness of the crushed stone layer should be 20-30 cm. This will perfectly protect the foundation of the house from the influence of groundwater.

After compaction, you need to waterproof the side of the formwork and the cushion itself. This is necessary to ensure that the cement mortar does not seep into the ground.

In order for the foundation structure to be strong, it must be poured immediately. You should not fill the foundation in parts, as its strength will decrease.

3. Before pouring the solution, a reinforced frame made of reinforcement bars with a diameter of 12 mm is lowered into the formwork. Once the frame is installed, pouring can begin. It is very important that no air bubbles are created during this process. To do this, the solution must be constantly pierced with a shovel or rod, and also compacted from time to time.

Floating foundation in pits and trenches flooded with groundwater

If water begins to come out when digging a trench, then it will not be possible to make a solid foundation. Not only will the cement not completely absorb water, but it will also become completely fragile, and due to dirt, unnecessary substances will get into its mixture.

In order to be able to build a foundation in trenches filled with water, it is necessary to install drainage. The remaining construction work corresponds to the construction of a floating foundation in dry trenches and pits.

How to install drainage in soils with high groundwater levels

Drainage - removal of water from the surface of the earth and removal of underground water using a system of drainage pipes, trenches, wells, canals, pumps and other devices.

To lower the water level in the trench, it can be pumped out with a drainage pump. However, if, while using the pump, small keys appear at the bottom that push out water, then pumping should be stopped. In this case, the use of a drainage pump in certain areas will not produce results.

We offer 2 ways to install drainage:

1. Open drainage is the easiest way to drain small amounts of excess melt and storm water. To install an open drainage system, drainage ditches are placed on the site, most often along its perimeter. Water from such ditches is drained into a common drain using drainage pipes. This type of drainage is most effective when the land is located on a slope.
2. A closed drainage system is designed to drain and prevent the rise of groundwater using a system of underground drainage pipes. A closed-type drainage device is a carefully designed system of pipes and drainage wells laid in a trench. A filter layer of sand and crushed stone is made at the bottom of the trench, then drainage pipes are laid on it. To avoid silting of drainage pipes, it is necessary to line the trench with geotextile. In a closed drainage system, pipes are laid below the groundwater level. A drainage layer of sand and crushed stone is created on top of the pipes, which is then covered with soil and a layer of turf.

In places where drainage pipes turn, inspection wells are installed, the size of which depends on the depth of the pipes.

If it is not possible to drain the water when draining the entire area, then you need to consult an experienced geologist.

Protection of the foundation from the influence of groundwater

1. Drain the entire area. After this, install waterproofing around the foundation, and upon completion of construction work, make a reliable blind area to protect the foundation from external water. For this purpose, you can also build a sidewalk along which water will flow.
2. The foundation is protected with cement-sand mortar, the layer of which should be 25 mm. The mixture is applied to the surface, leveled, and then thoroughly dried. A layer of roofing felt or ordinary roofing felt is attached on top.
3. Using mastic from heated bitumen and fluff lime in a ratio of one to two. If necessary, lime can be replaced with sifted dry chalk, which is mixed with regular resin in a one-to-one ratio. This molten mastic is applied to the surface in two layers, their total thickness is 8 mm.
4. The foundation is insulated with two layers of roofing felt or roofing felt. When laying, an overlap of 15 cm should be ensured. When laying, care must be taken that the rolled material is not damaged or has any defects.

Soil heaving in areas with high groundwater levels

You should not miss the fact that on soil with a high level of groundwater, during the frosty period the soil will heave greatly. Therefore, to reduce the pressure of such soils on the foundation, you need to waterproof the base of your building as best as possible.

If you have to build a house on soil with a high level of groundwater, it is important to choose the right foundation and materials for its waterproofing. In this situation, we recommend that you consult a specialist.

The construction of a house can occur on almost any type of soil, but when installing a structure on soil saturated with water, it is necessary to carefully select the type of foundation. It is also important to accurately determine the depth at which the base should be installed. The strength and durability of the structure depends on taking into account all the features. In areas where groundwater is too high, screw piles are often installed. A floating monolithic foundation is also often created.

Drainage works on the site

The simplest option for getting rid of water is to raise the area by at least half a meter. But it is worth remembering that carrying out such work requires large expenses. To do this, you need to fill the area with dry sand or soil, and then level the surface using a bulldozer.

A less expensive option is to create a network of canals throughout the site. After such actions, water will collect in ditches. The depressions are created in the form of open trenches, which are reinforced with clay. If desired, you can install gratings on them so that they do not spoil the appearance of the area.

If desired, you can create closed-type ditches, which are asbestos-cement pipes with perforations. When designing ditches, it is worth carefully studying the site to take advantage of the features of its topography. Ditches are created across the slope, as in this case they allow water to be collected more efficiently. It is worth remembering that if the site is located on a plain, it is necessary to make ditches with a slope. But it is important to take into account that the slope should not be more than 5 cm per 10 meters of length.

The drainage system must discharge water into a roadside ditch or into a specially created reservoir.

Features of a monolithic foundation

A monolithic reinforced concrete base is a fairly reliable support for the structure. It helps distribute the load over a large surface, so it rarely collapses. This type of foundation is often used in areas with high groundwater levels. The monolithic base resists soil pressure well during soil heaving.

A classic monolithic foundation should be created if the site experiences a seasonal increase in groundwater levels. This base option allows you to build a basement. If the house is being built in a swampy area or near a pond, it is worth creating a monolithic foundation on a floating pad.

Floating foundation

The specified foundation type is created as follows:

1. First, a pit is created. It is worth remembering that its bottom should be lower than the groundwater level. If this condition is not met, the lower part of the foundation will be in conditions of high humidity. This can lead to gradual destruction.
2. After this, geotextiles are placed at the bottom. This is necessary to prevent mixing of the backfilled sand with the underlying soil.
3. At the next stage, the formwork is installed and sand is poured. The thickness of the layer should be about 20 cm. After backfilling, the sand must be moistened and compacted using vibrating plates.
4. Then gravel or crushed stone is poured onto the sand. The thickness of the poured layer should be 20 cm. After completing the compaction process of the sand and gravel cushion, it is necessary to cover it with waterproofing material. This is necessary to prevent water from the cement composition from entering the soil.
5. Next, the reinforcement frame is created. The reinforcement must be a single structure, all elements of which are securely fastened together. After this, it is important to check the reliability of the created structure.
6. At the final stage, concrete is poured. It is important to ensure that no voids are formed during pouring. Their appearance can lead to the gradual destruction of the foundation. To prevent voids from appearing, a construction vibrator should be used. The surface of the mixture after pouring is leveled with a shovel. In order for the structure to be strong, it is important to pour it in one go, without dividing the concrete into layers. To do this, you need to order a machine with concrete, since you won’t be able to mix a large volume of mortar yourself and pour it right away.

It is worth noting that the monolithic foundation is quite reliable and allows you to create a basement floor. If water constantly accumulates in a dug pit, it must be pumped out using pumps or drainage work must be carried out throughout the entire area to reduce the groundwater level.

Features of a columnar foundation

Such a foundation resists soil deformation well during freezing of groundwater in the area. To create such a foundation, it is necessary to drill holes in the soil into which reinforcement will subsequently be installed. The walls of the pits are covered with roofing felt, after which concrete is poured. The surface of the drying composition is covered with polyethylene. This is necessary to ensure that the concrete does not crack during drying.

It is worth noting that with such a foundation it is impossible to create a basement. In this case, the bearing capacity of the foundation is limited. That is why, when the groundwater level is high on the site, a monolithic foundation is chosen.

Pile foundation

This type of foundation is used to create houses in wetlands, as well as in areas that are located in flooded areas. Examples include the areas around St. Petersburg, Amsterdam and Venice.

When creating such a foundation, piles are driven or screwed into the soil using special equipment. It is best to use screw steel piles coated with zinc to create the base. During installation, they compact the earth, which helps increase the stability of the support. But it is worth remembering that a pile foundation does not allow building a basement.

If you want to create a house with a basement in an area where the groundwater level is high, you should choose a monolithic base on a floating cushion. This option is quite reliable and protects the structure from groundwater.

How to make a floating foundation

The floating foundation pie consists of several layers:

• sunken soil;
• a layer of compacted sand and gravel;
• concrete base, which is a monolithic slab;
• vapor barrier;
• heat-insulating material;
• waterproofing layer;
• reinforced concrete screed.

It is worth remembering that the technology for creating the type of structure described may differ depending on the characteristics of each case. The creation of a foundation is influenced by the type of soil, terrain features and the structure itself. For example, if the structure is massive, the foundation must be created in such a way that it can withstand heavy loads.

The foundation construction process consists of several stages:

1. Creation of a pit. Its dimensions must correspond to the dimensions of the future foundation. The depth of the pit depends on the distance from the soil surface to the groundwater. This parameter is also affected by the level of soil freezing. After creating the pit, its bottom must be carefully compacted around the entire perimeter. It is worth remembering that you should not leave areas filled with sand or moisture.
2. Laying a sand cushion. In cases where groundwater is located too close to the soil surface, geotextiles should be used. This material is laid around the entire perimeter of the created pit. This will prevent the material from washing out. Each layer of sand and crushed stone must be thoroughly compacted using a vibrating plate.
3. Pouring concrete . Concrete grade M100 is usually used for the foundation of the house. The thickness of the foundation should be about 10 cm.
4. Laying waterproofing film. All seams of this material must be sealed. After completing such work, it is necessary to wrap the edges of the foundation film. This will help protect the base and the entire structure from moisture.

It is worth remembering that the waterproofing layer should be created only after the concrete solution has completely hardened. If you wait less than the allotted time, the foundation will be fragile and will begin to collapse already during the construction of the house. The reinforced concrete slab will be laid on the created structure.

Creation of a reinforced concrete structure

To create a foundation, a reinforcing metal mesh is laid on the waterproofing layer, after which the concrete solution is poured. The concrete grade M300 is used for it. After this, you need to wait a certain amount of time until the concrete dries and hardens completely.

If there is a need for this, communications are laid during the pouring of such a foundation. In this case, the pipes must be laid simultaneously with the pouring of the foundation. It is worth remembering that filling should be carried out without interruptions. If this rule is not followed, the strength of the foundation will be low and it may begin to collapse. This is especially important when creating a foundation on loamy soils and in areas with high groundwater levels.

In some cases, when creating such a structure, concrete blocks are laid, which are mounted in the form of supports on a concrete base. But such actions are performed quite rarely, as this increases the cost of the work. However, the strength of such a foundation is not great enough. When creating a prefabricated foundation, it is best to fill the pillars with concrete and then cover them with a layer of rubber, which will protect the base from moisture. If you take into account all the described rules for creating a foundation, you can make a reliable foundation for a house, even if the groundwater is located close to the soil surface.

Materials and tools

Before creating the foundation, you need to prepare all the necessary tools and materials in advance. To create a monolithic floating base you will need:

1. Tools for digging a pit. Before using heavy equipment, it is important to correctly determine the digging depth. If calculated incorrectly, the foundation will be washed away by groundwater.
2. Sand and gravel
3. Vibrating plate. This tool is required if the base is installed on soil saturated with moisture.
4. Polyethylene film, which is necessary to create a waterproofing layer.
5. Vapor barrier membrane
6. Insulation. Often, when creating a monolithic foundation, foam slabs are used. This material does not shrink and is not susceptible to the negative effects of moisture.
7. Concrete solution. It is important to choose the right grade of concrete so that the foundation does not crack under load.
8. Steel rods and tying wire to create a reinforced frame.

At the preparatory stage, it is important to check the availability of all materials and tools so as not to interrupt work while pouring concrete.

In some cases, in addition to the materials described, concrete blocks are used. It is worth remembering that if the groundwater level is high on the site, you can choose one of several types of foundation for the house, rather than focusing on the common option. These include a floating foundation, piled and prefabricated monolithic, which requires concrete blocks. A strip foundation is not created in such areas, since it does not contribute to the uniform distribution of moisture, which is why it begins to deform.

Since water is an integral part of our planet, it permeates even the upper layers of the soil. Not deep under our feet, under the upper layers of the earth there is groundwater that can interfere with laying the foundation of a building.

The problem of groundwater in the regions of Russia

According to data at the end of 2015, the problem of close groundwater is characteristic of some territories of the Novgorod, Kaluga, Yaroslavl, Volgograd, Ulyanovsk, Saratov, Samara regions, the Republics of Dagestan, North Ossetia, and the Perm Territory. Also, the position of groundwater levels above the average long-term depth by 10-30% was noticed in the south of Western Siberia in certain areas of the Novosibirsk region.

Autumn-winter minimum groundwater levels are higher than the long-term average depth by more than 30% of the long-term amplitude within certain territories of the Republic of Tatarstan and the Perm Territory. In the south of European Russia, such levels were observed in certain areas of the Volgograd region.

The most flooded areas of Russia are located in the south of Western Siberia in the territories of Omsk, Novosibirsk, Tomsk and Kemerovo regions. The highest position of groundwater levels is within certain territories of the Republic of Tatarstan and the Perm Territory, and in the south of Western Siberia - within certain areas of the Omsk and Tomsk regions.

The groundwater level varies depending on the time of year, but is constant in the same seasons. As a rule, the lowest water level (several tens of meters) is observed in rocky areas and areas with low moisture content in the ground and air. On the contrary, high groundwater levels are recorded at the end of winter and spring; this is primarily due to the melting of ice and snow.

Harm to groundwater for buildings

Close groundwater can cause a number of problems, the most popular of which are: gradual destruction of the foundation, flooding of the basement or summer cottage. Such a house will not last long, so it is very important to find out in advance the height of groundwater using engineering-geological studies, which can be carried out independently with proper preparation or contact a special organization engaged in this type of service.

Types of foundations

There are several types of foundations and each of them differs in the type of materials, design, as well as the specifics of its pouring. The choice of foundation depends on your budget, the soil characteristics of the site and the design of the house.

TO main types of foundations include strip, slab, columnar, pile and floating.

Tape

Strip foundation technology consists of several reinforced concrete strips located under the external and internal walls of the building, which can be made of stone, concrete or brick. Strip foundations are also suitable for houses with heavy floors, or if a garage or basement was planned for the house.

Hard. Foundation with a longitudinal reinforcing belt made of reinforced concrete.

Flexible. Foundation with a transverse-longitudinal reinforcing belt made of reinforced concrete.

Monolithic. Wide bonded reinforcement frame filled with concrete. Used when the groundwater level is high, as well as in the presence of weak soils.

Made. Concrete and reinforced concrete blocks, which are connected to each other with cement, which gives the structure strength. Such a foundation is laid to the depth of freezing of the ground, and is used in the construction of multi-story buildings with concrete floors at any time of the year, since this foundation has a high load-bearing capacity.

Shallow. It is used, as a rule, in the construction of small garden houses. Two rows of blocks are laid above the soil freezing level.

Deeply buried. Used in the construction of large buildings with several floors. Three to four rows of blocks are laid below the soil freezing level.

Slab

Slab foundation technology is one large monolithic slab of reinforced concrete, which can be laid at any groundwater level and on all types of soil. It is usually used when constructing a small house, due to the fact that a lot of budget funds are spent on laying such a foundation.

Columnar

Columnar foundation technology is a structure made of pillars located in all corners of the building, where walls intersect, under supports and other points with high loads. The pillars can be made of stone, brickwork, as well as concrete and rubble concrete, and they are 1.5-2.5 m apart from each other. Foundations of this type are used in places where the upper layers of the earth cannot be load-bearing.

Monolithic. It is used in cases where heavy loads are placed on the frame columns.

Made. Consists of stone blocks or concrete. Its advantage is the high speed of construction, but it must be taken into account that the seams of a structure made from such blocks are not reliable enough.

Pile

Pile foundation technology It is a structure of vertically or at an angle installed piles, which are stuck with their pointed end into the soil. To make this entire structure stronger, the upper part of the piles is additionally connected with beams. This type of foundation is very popular, and it is used when building on weak soils, due to the fact that the piles rest on harder layers of soil, passing through layers that are unsuitable for foundations.

Reinforced concrete shell piles. Such piles are installed with special vibratory hammers. They are used if it is necessary to remove excess soil, after which the resulting cavities are filled with concrete mixture.

Screw. The technology of a screw pile foundation has appeared relatively recently, and such technology can be innovative due to the fact that it allows you to quickly build a foundation due to its design. It is also worth noting the reliability of such a foundation, because each pile takes on a load of 2 to 5 tons. screw piles are buried in the soil using a capstan.

Printed. When installing such piles, the technology of forced displacement of earth is used. Concrete mixture is poured into the resulting wells.

Driven. With this technology, special hammers and vibration crushers drive piles into the ground. Unlike the ramming technology, the soil is not removed to the surface.

Floating

Floating foundation technology– the best option if your site has a very high groundwater level. Therefore, the stages of its installation will be discussed in more detail. The first stage is the installation of a ring drainage system, which serves to collect and remove groundwater. Next, you need to dig a pit or a trench, the bottom of which will be compacted using a special vibrating plate about 40 cm high (you need to consult with the builders, based on specific conditions). The dug trench is filled with sand, after which it is compacted, forming a “floating” cushion approximately 50 cm thick, on top of which, in turn, waterproof fabric is laid so that the fine soil does not sag.

Then you need to pour 15-20 cm of crushed stone on top of the fabric, after compacting it you need to lay roofing felt.

Formwork located in a trench/pit, is made of lumber. Then they are supported with pre-prepared shields and reinforced with timber spacers. The next step is the installation of the reinforcing mesh. Using two rows of reinforcement grade A-3 with a cross-section of 12 mm and a cell size of 20/20 cm, monolithic slabs are reinforced. The rods are cut in advance and installed vertically in such a way that the gap between the bottom of the slab and the top of the formwork should be 5-7 cm. And the last step is to reinforce the foundation strip. A frame mesh is created from four rows of longitudinal rods, which are connected by transverse rods.

Innovative ways to combat groundwater

Septic tank

A high water level in the ground at a summer cottage can interfere with the creation of an individual sewerage system. One of the common new and relatively inexpensive ways to deal with nearby groundwater is septic tank installation, made of sheet polypropylene with thick walls.

The operating principle of a septic tank is as follows:

• The first compartment receives drainage from pipes that come from the house. In this part, under the influence of bacteria, the wastewater breaks down into sludge, gas and clarified water.
• In the second part of the septic tank, filtration of small particles continues.
• The third part is a biofilter, into which the remaining particles in the second compartment do not fall.
• The fourth section accumulates purified waste liquid. As soon as the level of wastewater in the chamber overflows, the float pump activates pumping, which pushes clean water into the drainage system located above the groundwater level.

Such a device can boast a service life of 50 years, provided that it is cleaned with sewer machines. And at the same time, thanks to the septic tank, the high water level in the ground will not affect the sewer system in any way, which is the best solution to the problems of high water for those who live in a private house.

Drainage system

The second option for combating groundwater is installation of a drainage system. To combat nearby groundwater, you will need a surface drainage system that will take all the water and carry it into the nearest well.

The main stages of creating drainage:

• First you need to dig a trench 1 meter deep and 0.5 meters wide.
• It is imperative to maintain a slope of 2-3 percent towards the well, ditch or reservoir. If there is no slope, the water will stagnate.
• It is necessary to place drainage pipes in the gravel layer.

It is worth noting that if you regularly take proper care of your drainage, it will last up to 50 years. Complete drainage cleaning should be done every 10 years. Also, to prevent the system from freezing in winter, it is advisable to buy a special heating device, otherwise in the spring the entire summer cottage will be flooded.

The foundation plays a very important role - accepting and distributing the load from the main structure. An important factor when choosing the type of foundation is the groundwater level. When the groundwater level is high, building a foundation requires a lot of effort and material costs. In addition, laying the foundation in such conditions is carried out in strict compliance with certain rules that help reduce the impact of this negative factor.

Impact of high groundwater levels on the foundation

The basis of any foundation is a concrete solution, so the close location of groundwater has a harmful effect primarily on it. More precisely, concrete is not afraid of water itself; the destructive effect is exerted by salts and chemicals that are part of soil water. As a result of their influence, the frozen solution becomes loose and begins to exfoliate. The first signs of concrete deterioration are stains and mustiness.

Another harmful effect of high groundwater is the erosion of the bottom of a trench or pit by incoming water, as a result of which the bearing capacity of the soil decreases, deformation occurs, and. This problem can be solved by constructing a drainage system and draining water.

What to consider when choosing a foundation

When choosing a foundation for building a house on a site with a high groundwater level, you should take into account various factors:

• What load will the main structure exert on the foundation? In other words, what material will be used in the construction of load-bearing walls.
• Will the house have a basement or ground floor?
• To what depth does the soil freeze in winter?
• How high does groundwater rise during a flood, and how long does it take for it to return to normal?

Taking into account these criteria, the foundation with a high groundwater level can be of several types:

• - This is a reliable structure, but unprofitable in material terms. The slab foundation can be built on the surface or deep in the ground. When planning a basement or ground floor, a monolithic slab is installed at a depth of about 2.5 meters. For greater strength, you can place a monolithic base on piles. At the same time, a structure is installed under the slab to prevent water from entering the basement.
• is the most popular option among private developers. However, it can be used with some restrictions: groundwater rises at a certain period or is located below the freezing level of the soil. The high location of groundwater allows the construction of a reinforced concrete strip in the upper layers of the soil. In this case, the load on the base must be taken into account in order to prevent its subsidence or destruction. When choosing a strip base, you should remember that in this case there will be no basement in the house.
• is one of the reliable options. Such a foundation can be made on metal, screw, reinforced concrete or bored piles. Their installation is carried out after accurately determining the depth of the dense soil layer. You can also pour the support yourself rather than using a finished product. To do this, you need to strengthen it with a reinforcement cage and fill it with concrete mortar.

Installation of a drainage system in areas with high groundwater levels

The construction of foundations, the base of which is supposed to be built below the groundwater level, inevitably leads to the use of various methods of water reduction. In other words, options are selected for removing water from a pit or trenches and keeping it at a certain distance.

Drainage involves the removal of melt and groundwater. To equip the system, drainage pipes, wells, channels, pumps and much more are used.

There are 2 ways to install a drainage system.

Open depression

You can pump out water with a drainage pump, but in this case certain conditions must be met:

• There is a reservoir nearby where the pumped water will flow.
• No visible signs of suffusion. With this phenomenon, the smallest particles of soil are carried away along with water, which leads to subsidence of the soil layers located above. The bearing capacity of such soils is very low due to constant subsidence.

Also, the open dewatering system involves a simplified version of the disposal of melt, ground and storm water. To organize such a process, drainage ditches must be placed around the perimeter of the site. Water of various origins flows into them for one reason: the absence of soil resistance and capillary rise of liquid. Such systems are most effective if the site is located on a slope.

Closed drainage system

Closed drainage helps drain groundwater, thereby preventing it from rising. The basis of the system is underground pipes. A closed drainage is a carefully planned structure of pipes and wells. The system is located in a trench, the bottom of which is covered with sand and crushed stone, and also covered with geological fabric. Pipes of a closed drainage system are laid under groundwater. The top is covered with an additional layer of sand and crushed stone, which helps drain water. The entire system is covered with soil and a layer of turf.

Floating foundation in conditions of high groundwater levels

If the structure being built is too heavy, for example, a brick house, then it is better to opt for a floating foundation.

This type of foundation can be built in a dry trench or pit, or in depressions filled with groundwater.

Floating foundation in a dry trench

To arrange the foundation in these conditions, you must perform the following steps:

1. They dig a trench about 1 meter deep and 0.5 meters wide and cover the bottom with geological textiles. This material will prevent the bedding from moving if water washes away the soil.
2. To give the foundation a rectangular shape, formwork is made.
3. Construct, the thickness of which should be 0.2 m. Gravel or fine crushed stone is poured on top of the sand. The thickness of this layer should be equal to or slightly greater than the sand cushion. Such a foundation will be a good protection for the foundation from groundwater. Each layer to be poured must be compacted thoroughly.
4. The walls of the formwork and the cushion of sand and gravel are covered with waterproofing material, which will not allow the concrete solution to seep into the soil.
5. Do not forget about the frame made of reinforcing bars. This design increases the reliability and stability of both the foundation and the entire house.

Floating foundation in trenches flooded with water

When the groundwater level is high, the dug pit or trench is filled with water. Under these conditions, building a reliable foundation is simply impossible. The concrete solution will absorb water, and dirt can cause unnecessary substances to enter the concrete, which inevitably leads to a decrease in its strength.

When planning the construction of a foundation in such conditions, it is important to properly organize water drainage and develop a drainage system. Otherwise, the work is carried out similarly to the construction of a floating foundation in dry trenches.

Methods to protect the foundation from the effects of groundwater

Construction of a house on a site with a high groundwater level requires mandatory work to protect the foundation from the negative impact of this factor.

1. An effective system for draining water of various origins is created throughout the site. Then they make a reliable one, which will prevent external water from penetrating to the base.
2. A sand-cement mortar is applied to the surface of the foundation in a layer of about 2.5 cm. The protective coating is well leveled and left until completely dry. Then the foundation is covered with roofing felt.
3. Mastic is prepared using lime powder in a ratio of 1:2. The mixture is applied to the surface of the foundation in two layers with a total thickness of no more than 8 millimeters.
4. Waterproofing is carried out with roofing felt or roofing felt. In this case, the material is laid in several layers, overlaying strips of 15 cm. When using this method, it is important to check the material for damage and defects.

Building a foundation with high groundwater requires careful consideration of each step, the correct choice of foundation, taking into account all positive and negative factors.

A foundation with a high groundwater level is one of the most complex and critical structures.

Such a foundation for a house must be built taking into account many different factors, each of which must meet all the requirements associated with the danger of flooding and premature destruction of the building.

Accordingly, it is important to correctly determine the level of soil freezing, select the most suitable foundation design and ensure the presence of an effective drainage system.

Determining groundwater levels and possible concerns

Ground water level

The construction of the foundation at a high groundwater level must be stable and reliable. The extent of the threat of subsidence and destruction of the building is determined long before the start of construction work. For this purpose, in the spring or autumn (at a time when the amount of moisture contained in the soil reaches its maximum level) in the place where, in accordance with the construction plan, the basement will be equipped, a hole should be dug at least 3 m deep.

Dig a hole at least 3 m deep

To obtain accurate data, you will need to reliably protect the pit from weather precipitation. After a few weeks, a certain amount of water will appear and settle at the bottom. Perhaps the bottom will remain dry, and then the foundation does not require additional protection.

If the water is located at a distance above 2 m from the surface, it is necessary not only to calculate the depth at which the foundation will be built, but also to choose the right structure.

What should the foundation be like in case of high groundwater, experts can say after conducting geological surveys.

Piles will raise the level of the house to a safe height

Among the existing foundation structures on high-level groundwater, pile structures are especially popular and trusted by consumers.

Their arrangement will help ensure high-quality and reliable protection of the foundation of the house from the negative influence of groundwater:

• flooding of basements;
• destruction of concrete structures;
• the occurrence and development of fungus and mold;
• violation of the integrity of the foundation itself when freezing during the cold season.

At high groundwater levels, the walls of the pit may float

In addition, high groundwater level causes the walls of the pit to melt and a sharp reduction in the bearing capacity of the soil. This will require additional work to develop an effective drainage system, including wells and catch basins.

The most dangerous process is the leaching of minerals from the soil, which significantly worsens the strength characteristics of the soil and leads to a change in its structure. Installing a foundation in such conditions has a number of limitations. Calculation of the depth at which the supporting structure will be poured is carried out taking into account the qualitative characteristics of the soil:

• loams;
• sandy;
• clayey;
• mixed.

The level of heaving and the depth of soil freezing depend on this. If the freezing depth is less than the ground level, then there is no need to make adjustments for soil characteristics when planning.

The calculation is carried out with adjustments for soil type and possible subsidence of soft soils.

The data obtained most often forces one to abandon the construction of a strip structure, since the associated work will be very labor-intensive and require significant material costs.

A variety of foundations and the correct choice of the desired design

A slab foundation is suitable for clay soils with high groundwater level in a shallow version

What kind of foundations are needed for houses, if groundwater is close, is chosen depending on the various features of the site itself on which construction is being carried out. A foundation on water is a structure that should ensure the stability of the building, its durability and reliability. To do this, it is necessary to take into account both the quality of the soil and the upcoming loads coming from the building.

Construction of a foundation on clay soils with a high groundwater level involves the construction of any type of foundation:

• belt, the trenches of which are deeply buried;
• pile;
• slab (shallow).

The strip base requires the creation of a monolithic reinforced concrete structure located under the external and internal load-bearing walls.

The depth of the trench must exceed the freezing height

First of all, markings are made on the site, according to which they dig pit trenches for the strip foundation. Their depth must exceed the freezing height. The calculation is carried out adjusted for the characteristics of weather conditions (temperatures in winter) and soil.

If groundwater is close, and construction will be carried out on clay, a strip foundation will perfectly replace a “floating” monolithic slab. The weight of the building is evenly distributed over the entire surface of the slab, which is laid on a sand and gravel bed.

Before making such a foundation, you will need to remove soil from the entire area of ​​the future foundation. The pit is dug to a depth 50 cm greater than the thickness of the slab. The calculation is based on the soil freezing depth.

A pile foundation for a house is the best option for creating a high-quality, reliable foundation on clay soils.

By changing the parameters of the piles, it is possible to install supports on hard rocks that are not subject to destruction under the influence of groundwater.

To carry out work in an area with high groundwater level, it is necessary to calculate the load on each individual pile.

Construction of various types of foundations

If groundwater is close to the foundation site, then before you begin constructing a slab foundation, you will need to prepare ditches along the entire perimeter of the future building. It is better if it is a trench 20-30 cm wide and at least 50 cm high (depth). The ditches will be filled with rain or melt water, and thus drainage will be carried out. For more information about the preferred type of foundation, watch this video:

To protect the foundation walls, treat them with waterproofing mastics

The “floating” slab does not lie on clay soil, but on a cushion created from sand and gravel. This type of foundation must be poured by building it on bulk soil. Before pouring, install a drainage system, laying drains at a slope of at least 5 cm for each meter of pipe. To protect the slab, it is necessary to line the inner surface of the base with waterproofing materials. Most often, roofing felt is used, laying overlapping sheets 10-15 cm wide. Fastening is done using bitumen.

A reinforcing frame is laid on the waterproofing and filled with concrete, the filler of which is fine gravel. It is better to fill the entire base in one day.

A strip foundation requires careful preparation of the pit trenches. They must be deep and wide enough to exceed the freezing depth of the ground and allow the formwork structure to be assembled efficiently.

The monolithic tape is poured, taking care of the correct filling of its bottom, high-quality compaction and installation of waterproofing. A frame is installed inside the formwork, connected from reinforcing bars of various sections. Concrete is poured in layers with mandatory compaction of each layer. For useful tips when building a house on soil with high groundwater level, watch this video:

The pile grillage foundation is recognized as the most reliable when constructing buildings in areas with high groundwater level. When making such a foundation, it is important to follow soil indicators, depending on which the size of each of the piles used is determined. Piles are used:

• screw;
• bored;
• driven.

Screw structures can be installed independently without the involvement of heavy construction equipment. After installing all the piles, a grillage is assembled on them or a beam is laid, which is necessary to tie the entire structure together.