Foundation in a swamp: choosing a foundation. How to make a foundation in a swamp: technology for constructing a slab foundation What kind of foundation for a bathhouse in a swamp

Construction of the foundation is one of the most expensive stages in the construction of a private house. In swampy areas, this process is complicated by soil instability and the need to perform additional amounts of work: filling access roads for construction equipment, installing a drainage system, and due to high humidity, installing high-quality waterproofing of all elements of the building.

Reliable foundation for marshy areas

The developer can choose either reinforced concrete or steel screw piles as the foundation for his house. Swampy soils are characterized by a high groundwater level, so concrete, which tends to gradually deteriorate from moisture, must be protected from its effects. For this purpose, you can use water repellents, which will increase the service life of the piles by 10-12 years. These are impregnations Aquasol, Elakor-MB4, Gidrotex-F, waterproofing mastics based on bitumen. A foundation made of screw piles is more reliable and durable, but it also needs additional protection: it is recommended to coat these products with anti-corrosion primers or paints.

Pile foundations in swampy areas are beneficial for several reasons: firstly, these supports can be installed in the deepest, most stable layers of soil, bypassing sticky soil, which will ensure the reliability of the foundation. Secondly, piles allow you to build a house in areas with difficult terrain, where there are significant differences in elevation. Thirdly, steel or reinforced concrete supports can flawlessly withstand the load not only of a private low-rise building, but also of more massive buildings.

Is it possible to build a strip foundation on a swampy area?

A strip foundation is a budget solution for individual construction, so many developers tend to use this option. But for swampy areas it is not always economically profitable, since the construction of a reinforced concrete strip will require the following list of expensive works: stabilize the soil to the freezing depth (build drainage communications), remove the top layer of soil (on average, up to 40 cm), backfill the site under the house using gravel and sand, level and compact it.

Due to the risk of repeated waterlogging of the soil due to the characteristics of the soil, the concrete strip is built only on a base of road slabs (which can be either new or used). It is on them that the formwork is mounted and the strip foundation for the house is erected. Therefore, the construction of such a foundation will be comparable in price to the installation of reinforced concrete or screw piles, which are more reliable for this geology.

They are able to provide the building with stability, which is the main requirement for buildings on marshy soils. These soils are highly heaving, therefore any foundation that is not buried below the freezing point of the soil is unreliable. Therefore, the recommendation of builders when choosing a foundation for unstable soils is clear: piles.

Which is more profitable?

— with walls made of flexible timber or brittle aerated concrete? In each specific case, the answer to this question will be different.

How to make a foundation for a country house in areas with marshy soil.

Areas with weak, marshy soils are considered unfavorable for building a house in terms of soil conditions.

You can build a house on any soil, you just need to do it correctly.

Soil properties in wetlands

Wetlands are characterized highly compressible soils. Such soils include:

  • Loose sands and sandy loams, water-saturated, fluid-plastic and fluid consistency with a porosity of more than 41%.
  • Loams with a porosity of more than 50% and clays with a porosity of more than 52%.
  • Peaty sandy and clayey soils. Peat soils include soils containing less than 50% organic matter.
  • Peat is soil that contains more than 50% organic matter.
  • Silt is a highly porous, water-saturated sediment formed as a result of microbiological processes in water bodies. Soil porosity can reach 60%.
  • Sapropel is a water-saturated sludge containing more than 10% organic matter. Its porosity is up to 75%

All of the above soils have high humidity - up to 80%, and low load-bearing capacity from the weight of the house. For example, the calculated load resistance for sludge is 0.4-0.6 kg/cm2, for peat sandy soils – 0.4-2.5 kg/cm2.

Wetlands in areas can be of natural or artificial origin. Waterlogging can be the result of human economic activity. Sometimes waterlogging occurs after the construction of a house on the site.

Artificial swamping of the site is caused by:

  • Raising the general ground level during the construction of roads in the village and during construction in neighboring areas. As a result, the natural flow of water from areas located below is disrupted.
  • Construction of fences on a solid strip foundation without water passages.
  • Lack of organized storm water drainage on the site and in the village.

The process of artificial waterlogging usually lasts several years.

Due to high humidity and high groundwater levels soils in wetlands are highly heaving.

A house built on weak and heaving soils is at increased risk of destruction as a result of significant settlement and uneven soil deformations.

Even on a hard foundation the house may gradually sink into the swamp over the years. Under the weight of the house, water is gradually squeezed out of the pores of the soil, the soil under the house becomes compacted and the house gradually settles every year.

How to make weak soil stronger

The layer of weak marshy soil has different thicknesses in different areas. For example, in one area the layer of soft soil may be no thicker than 1 meter. On the other - more than 10 meters. Under the layer of swampy soil there is always a layer of low-compressible soil with “usual” properties for construction.

The load-bearing properties of weak soil can be improved in the following ways:

  • Peat removal – replacing swampy soil with a cushion of non-heaving soil. Replacement is carried out under the base of the foundation through the entire thickness of the swampy soil layer or partially.
  • Construction of the foundation on an embankment of non-heaving soil.
  • Compacting the soil under the foundation.

Building regulations prohibit the base of the house foundation from resting directly on soft soil. Therefore, pillows and embankments are a necessary element in the construction of a foundation on soft soils.

Features of the design of a house on soft soils

When building on swampy soils, constructive solutions are used aimed at reducing soil settlement by reducing the specific pressure of the house on the ground. To reduce the sensitivity of the house frame to uneven deformations, the rigidity or flexibility of the building's load-bearing frame is increased.

To reduce the specific pressure of a house on soft soil and increase the rigidity or flexibility of the building frame, the following design measures are used:

  • They increase the area of ​​support of the foundation on the ground through the use of a foundation - a slab or strip foundation with a widened base.
  • They increase the spatial rigidity of the foundation by installing a monolithic reinforced concrete foundation. (Prefabricated strip foundations made of blocks or masonry materials are not used.) Increase the rigidity of the slab foundation by installing stiffeners or making a foundation-plinth of increased height. Additionally, a monolithic reinforced concrete floor is installed, rigidly connected to a monolithic plinth-foundation.
  • The spatial rigidity of the building frame is increased by installing monolithic reinforced concrete belts at the floor level and reinforcing the masonry of stone walls.
  • Pile foundations are used with support on the underlying low-compressible soil layer.
  • On soft soils, it is advantageous to build houses from light and flexible building structures - logs, beams, frames. The cost of constructing foundations for such houses is much less than for fragile houses made of stone materials.

The task of choosing a foundation design and design features of the house frame comes down to determine the most economical option for specific construction conditions.

For example, which is more profitable– to excavate the entire depth of the swampy soil and make a strip foundation or install a pile foundation or pour a slab foundation on an embankment? Which house will be cheaper to build on soft soils?— with walls made of flexible laminated veneer lumber or brittle aerated concrete? In each specific case, the answer to this question will be different. The correct answer can only be obtained from specialists - designers.

Managers of construction companies usually try to impose a foundation option on the developer based on their interests; the more expensive the better. Or they may, in order to retain the customer, offer a very cheap option, which the developer will then bitterly regret agreeing to.

The figure below shows the construction of an artificial soil foundation and slab foundation for a stone house on weak, marshy soil.

Slab foundation for a one-story house with walls made of cellular concrete with brick cladding. 1 – thickness of weak marshy soil – 10 m; 2 – sand cushion; 3 – embankment; 4 – planning fill; 5 – foundation slab; 6 – base; 7 – waterproofing; 8 – blind area; 9 – groundwater level – 0.4 m from the surface.

Let's consider the measures taken by the foundation designers to build a house on weak, marshy soil.

To improve the construction properties of the soil at the base of the foundation:

  • Partial peat removal has been carried out - the plant layer of soil has been cut off in an area 300 thick mm. (slightly above the groundwater level). A sand and gravel cushion is installed in the resulting recess, item 2 in the figure.
  • An embankment, item 3, was made from non-heaving soil. The soil in the embankment is laid with layer-by-layer compaction. Under the weight of the fill soil, the underlying layers of weak soil become compacted and settle. It is recommended to start building a house 6-12 months after filling to give time for subsidence to stabilize.

After installing the slab foundation, additional leveling soil is dumped, item 4. Leveling filling is carried out with any soil.

Building a house on an embankment contributes to the overall rise in the surface level of the site and ensures the drainage of melt and rainwater from the house and the site.

The height of the embankment, item 3, can be reduced by increasing the thickness of the sand cushion, item 2, so that the total thickness of the bulk soil of the cushion and embankment remains unchanged. It should be taken into account that it is quite problematic to fill and compact the soil of the cushion in water below the groundwater level.

Structural solutions for constructing a foundation for a house in a swamp:

  • To reduce the pressure of the house on the ground, a slab foundation was used - a monolithic reinforced concrete slab under the entire area of ​​the house, position 5 in the figure. Moreover, the dimensions of the foundation slab are increased and extend beyond the walls by 300 mm. from each side.
  • The spatial rigidity of the foundation is increased by installing a monolithic reinforced concrete plinth, item 6, connected by reinforcement outlets to the foundation slab.
  • A monolithic reinforced concrete floor at the upper level of the plinth can further increase the rigidity of the foundation. The single structure of the basement box made of monolithic reinforced concrete is a fairly rigid foundation for a stone house.
  • The house has aerated concrete walls, and a monolithic reinforced concrete belt is installed at the floor level.

The foundation design shown in the figure was developed for rather difficult soil conditions: the soil is water-saturated silt with a thickness of 10 m., high groundwater level – 40 cm. from the surface.

For more favorable soil conditions, the volume of pillows and embankments, as well as monolithic reinforced concrete at the base of the house, can be noticeably reduced.

Gaining increasing popularity among private developers slab foundation option - insulated Swedish slab. In this option, insulation is laid under a monolithic foundation slab, and the stiffeners are directed downward into the ground. The foundation slab serves as the base for the walls and the base for the floor of the first floor. Some disadvantage of this foundation design is the low base. In conditions of significant thickness of snow cover in most climatic zones of Russia, increases the risk of dampening the lower part of the wall of the house.

The reinforcement frame for reinforcing the foundation slab of a private house usually consists of upper and lower reinforcing mesh and vertical connections between them. The number of reinforcement bars and their diameter are determined by calculation.

In the case of the construction of heavy two- to three-story brick houses in difficult soil conditions, it may be more profitable to build a foundation on driven piles.

On soft soils with a layer thickness of less than 3-5 m. the feasibility of building a house on bored or screw piles supported by the underlying low-compressible soil layer should be considered.

Shallow strip foundation for a house in a swamp

Houses with frame walls, as well as walls made of logs and timber, are more flexible and can withstand significantly greater deformations than stone houses. Such houses in the swamp can be built on shallow or non-buried strip foundations.


Shallow strip foundation for a one-story house with frame or wooden walls. 1 – thickness of weak marshy soil – 10 m.; 2 – sand-gravel (crushed stone) cushion; 3 – strip monolithic reinforced concrete foundation; 4 – leveling embankment; 5 – blind area; 6 – waterproofing; 7 – groundwater level – 0.4 m. from the ground surface.

The shallow monolithic strip foundation under the external and internal walls, item 3, is a single spatially rigid frame. In order to increase rigidity, the height of the foundation strip combined with the plinth has been increased. The wide base of the foundation is located at the level of the ground surface on a sand and gravel bed.


Strip foundation reinforcement scheme

For the foundation shown in the figure above, it is enough to make reinforcement mesh in the upper and lower chords from three longitudinal rods with a diameter of 12 mm, class A-III. The reinforcement bars in the mesh are connected by auxiliary ties made of BP wire with a diameter of 6 mm.

The upper and lower mesh are connected by vertical transverse reinforcement rods with a diameter of 8-10 mm, class A-III. Protective layer of concrete for foundation reinforcement of at least 5 cm.

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If you have been given a marshy area to build a house on, there is no need to be upset; with modern technologies it is possible to build a house on a marshy area. The main thing is to choose and build the right foundation - the foundation for the house. And we'll tell you which foundation is better on swampy soil.

This is a multilayer heterogeneous structure, which includes clay, peat, sandstone and has different densities. It is oversaturated with moisture, with a large number of fine-grained particles that weakly resist compression. The instability of the soil makes it difficult to determine the maximum load it can withstand. Therefore, swampy soil is considered the most difficult for building a house. Before determining the type of foundation, area and depth of its foundation, a thorough study of the geological situation of the site is necessary.

Geological soil studies

They are needed to determine basic soil indicators. These include:

  • volume of soil water;
  • soil type;
  • soil freezing level;
  • surface proximity of groundwater.

It is necessary to use a manual probe to sample soil. At least 4 wells need to be drilled on the site (in the corners of the future foundation). It is better to do this in the spring, when the soil is most saturated with moisture. Soil sampling provides the following information: composition, physical properties and thickness of the layers, their depth, changes in the soil over the past few years.

For a wooden house you need to drill a well 5 m or more deep, for brick or stone houses - 8–10 m. DIY foundation on swampy soil can be built if professional geologists assess the condition of the soil.

It is important to consider the depth of soil freezing. Insufficient foundation depth can lead to its destruction. Information obtained as a result of geotechnical research will help determine the type of foundation that will suit you.

Types of foundations for swampy soil

Work on arranging the foundation is the most labor-intensive and expensive stage of construction, which on swampy soil accounts for at least one third of the total cost estimate for building a house. Many years of research have shown that any foundation on swampy soil begins to collapse after a few years if it does not reach the depth of seasonal freezing. On the south side, where the soil moisture is greatest, it begins to “stick out” from the ground if done incorrectly.

Therefore, in order to foundation, erected in the swamp with your own hands, served for a long time make a drainage system. It makes it possible to drain excess water from the site. On swampy soils, three types of foundations are used. Let's consider these types.

Pile foundation

This type of foundation is considered the most suitable for swampy soil. It has the following advantages:

  • relatively low prices;
  • short construction time (can be built in 2 days);
  • construction can be carried out on any terrain;
  • work can be carried out in any weather;
  • increased durability and corrosion resistance;
  • increased strength and stability.

The use of piles of different heights makes it possible to smooth out uneven surfaces of the construction site. Its main part is the pile itself, which can be installed vertically into the ground or by making a slight slope. They are combined using a grillage (a concrete pad in a reinforcement frame).

In swampy areas, the following types of piles are used:

  • Screw piles in a metal shell. They are protected from corrosion with mastic or zinc coating and screwed into the ground using a special lever.

  • Reinforced concrete piles (driven into the ground with a hand piledriver).

  • Complex combined piles. They are placed in a casing pipe, which is removed after the piles are installed and the site is concreted.

Slab foundation

Reliable, but one of the most expensive types. It can withstand sudden temperature changes and heavy loads. The uniform distribution of the weight of the building over the entire area of ​​the foundation does not allow it to sag, and the sand and gravel cushion located underneath allows groundwater to pass through without harming the foundation.

The construction technology is as follows:

  1. A shallow pit is dug (up to about 1 meter deep).
  2. It must be drained using drainage or using pumps (if there is a large amount of moisture).
  3. Layers of sand and gravel are laid at the bottom of the pit, which are carefully compacted and covered with several layers of roofing felt.
  4. To pour concrete, formwork is made and a reinforcing frame of at least 12 mm is constructed.
  5. The prepared area is evenly poured with concrete mortar and the slab is allowed to dry for several days. The formwork is dismantled.

The slab must be filled in one go. A strip foundation is erected on top of it. Such a foundation can be made on your own, it is durable, when shrinking it protects the walls from cracks, and allows you to build a basement floor.

Shallow strip foundation

This is the cheapest foundation, but is only suitable for light buildings made of wooden beams and metal frames. It needs a good drainage system, because it is laid above the freezing point of the soil. They make it only monolithic, which allows the shallow foundation, due to its own rigidity, to resist soil heaving, evenly rising and falling along with the soil. He also needs a good sand “cushion” and insulation of the foundation base.

Nowadays, lay DIY foundation in marshy areas and building a house using modern technologies is not difficult. The main thing is an accurate calculation and a great desire, the rest is a matter of technique. Go for it, you can succeed.

Example with specialist comments (video)

If your site, which you plan to use to build your house, has swampy soil, you should not be upset. Modern technologies easily make it possible to lay a foundation even in difficult conditions. The main rule in this case will be the correct choice of the type of base. You cannot make a mistake, because the service life of not only the foundation itself, but also the entire building, will depend on this.

What is swampy soil?

Before you begin building a DIY foundation in a swamp, you should become familiar with this type of soil. It is a heterogeneous multilayer structure, which provides for the presence of:

  • sandstone;
  • peat;
  • clay.

The swamp is always oversaturated with moisture and has large quantities of fine-grained particles. They resist compression quite weakly. The soil is unstable, so determining the maximum load is quite difficult.

Swampy soil is one of the most difficult for construction. Before determining the foundation depth, type of foundation and area of ​​the structure, it is necessary to study the geological situation.

Features of construction in wetlands: geological studies

If you decide to lay the foundation for a house in a swamp, then at the first stage you must carry out geological research. They are necessary to determine soil parameters. It will be necessary to find out what the volume of soil water is, to what level freezing occurs, the type of soil, as well as the surface proximity of groundwater.

To sample soil, you must use a hand probe. Wells are drilled on the site, which are located in the corners of the future foundation. It is better to carry out research in winter, when the soil is most saturated with moisture. Soil sampling allows you to obtain the following information:

  • thickness of layers;
  • physical properties of the soil;
  • depth of formations;
  • soil changes in recent years.

For a wooden house, 5-meter wells are drilled, while if you are planning to build a stone or brick house, then the depth of the well must be increased to 10 m.

Before starting construction on a wetland, the depth of soil freezing should be determined. If the foundation is laid at insufficient depth, this may subsequently cause its destruction. As a result of geotechnical research, you will receive information that will allow you to determine the type of soil.

Which foundation is better to choose?

The most labor-intensive and expensive process in building a house is the foundation work. The cost of these manipulations will be 1/3 of the total cost estimate for the construction of the building. After a few years, any foundation in a swamp begins to collapse, but only if it does not reach the depth of seasonal freezing.

On the south side, the base begins to bulge if the work was carried out incorrectly. In order for the structure to last as long as possible, it is necessary to make a drainage system. It will remove excess moisture from the area. On swampy soils, three types of foundation are used, one of them is pile.

This design is the most suitable because it has the following advantages:

  • relatively low cost;
  • the ability to carry out construction in any terrain;
  • increased durability;
  • high stability and strength;
  • excellent corrosion resistance.

Screw piles for the foundation can be installed in any weather. Construction time is very short. You can complete the foundation installation in 2 days. If you use supports of different heights, you can smooth out surface unevenness.

The main part of the foundation is a pile, which can be installed vertically or with a slight slope into the ground. The supports are connected using a grillage, which is a cushion in a reinforcement frame.

Screw piles for foundations are one of the types of supports used in swampy areas. These products are protected from corrosion by zinc coating or mastic. Screwing is carried out using a special lever. Piles can be reinforced concrete; they are driven with a hand pile driver. An alternative solution is complex combined piles that are placed in a casing pipe. They are removed after the supports are installed and the site is concreted.

Construction of a foundation based on bored piles

The foundation in a swamp may consist of bored piles. It is built using one of several technologies, including:

  • with waterproofing;
  • with permanent formwork;
  • with removable formwork.

Covers are installed in the drilled holes, which are welded from polyethylene film. The walls are lined with roofing felt, and concrete is poured inside. When creating a pile, you can use removable formwork made of metal or plastic. 2 hours after pouring, the strength of the concrete will be sufficient to preserve the structure. The formwork is pulled out after the mortar has hardened.

Such supports have one drawback, which is that they are not protected from moisture. But the impact of the frozen layer can be neutralized by creating a sand cushion.

A foundation on drilled piles in a swamp can be created using the third method, when the formwork is not removed. In this case, it will perform the function of waterproofing. The technology involves the use of pipes made of the following materials:

  • special cardboard;
  • asbestos cement;
  • metal

This method allows you to protect the piles by eliminating height differences and creating a layer of sand between the supports and the walls of the well. Before installing the structure, water from the well is pumped out by a pump. The lower part of the pipe, which acts as formwork, is filled with waterproofing concrete to a height of one meter.

Such a foundation in a swamp requires increasing the strength of the support. For this, frames made of metal 1.2 cm rods are used. You can also use triangular designs.

Should I choose a slab foundation?

One of the most expensive, but reliable is a slab foundation. It can withstand heavy loads and sudden temperature changes. The weight of the building will be evenly distributed over the entire area of ​​the structure, which will eliminate the possibility of subsidence. Under the slab there is a sand and gravel cushion that allows groundwater to pass through, preventing damage to the foundation.

Carrying out construction on a wetland. Slab foundation - is it suitable?

If the area has marshy soil, then you can build a slab foundation. At the first stage, a shallow pit is dug, and then it is drained using pumps or drainage. Layers of sand and gravel are laid at the bottom, which are well compacted and covered with several layers of roofing material.

To pour concrete, formwork is installed, and a reinforcing frame is constructed from 1.2 cm rods. The prepared area is filled with solution and then left to dry for several days. After this, the formwork can be dismantled.

Such a foundation in a swamp is poured in one go; a strip foundation can be installed on top. It is done on your own, is durable, and when it shrinks, it protects the walls from the formation of cracks. This technology is relevant for those who want to have a basement in their home.

An alternative option is a shallow strip foundation

A strip foundation in a swamp is one of the cheapest, but is only relevant for buildings made of a metal frame or wooden beams. Such a foundation requires a good drainage system, since the structure is laid above the freezing point of the soil. The tape must be monolithic, this ensures the ability to resist soil heaving.

The structure will rise and fall evenly along with the soil. The tape will require a sand cushion, as well as thermal insulation of the base. Such a foundation in a swamp can be poured independently, following the technology. The work is not too difficult.

Construction of a strip foundation

If you decide to build a strip foundation, then first you need to dig a trench of the desired shape. A sand cushion is placed on the bottom, and then a reinforcement frame is installed.

If water appears at the bottom, then you should get rid of it by constructing drainage. Next, the formwork is installed and the mixture is poured, which should be left until it hardens. When everything is dry, the surface is covered with waterproofing.

Finally

Peat bogs and marshy areas are some of the most difficult soils to build on. Wetland soils are oversaturated with moisture and are prone to the formation of unstable quicksand. In winter, such soil is subject to frost heaving, and in spring – erosion. The solid layer lies at a considerable depth, which excludes the possibility of using some types of foundation.

For wetlands, it is best to use floating foundations, also called monolithic slabs. The structure will be solid, thanks to this there will be no partial shift of the house, and distortions and destruction of the walls will be excluded.

Construction on marshy soils can be compared to an extreme sport due to the unpredictability of the results. The main problem of a house on swampy soil is the very poor bearing capacity of the soil and excess moisture. It is possible to build in such conditions only using a guaranteed effective and stable foundation. Not all options for foundation structures will be able to hold the building in a stable position for a long time.

Which foundation is best to use in swampy areas?

In each specific case, the choice of a specific foundation scheme depends on the condition of the soil, the level of groundwater and the types of soil in a particular area. Therefore, before making a decision, it is necessary to conduct exploration and assessment of the nature of the soil, sources of groundwater that flood the area, and the depth of solid rock layers.

Advice! If you can qualitatively assess why a given area is flooded and how to deal with the causes of flooding, you can reduce the cost of a foundation in a swamp several times.

Depending on the results of the study, you can choose the most optimal option for the foundation for the house:

  • Strip foundation with enhanced drainage and deep drainage. Although experts do not recommend using strip foundation systems for waterlogged areas, it can be used for a certain type of soil in a swamp. For example, for soil with a large amount of coarse river sand, with deep aquifers and the absence of natural springs and springs on the surface in close proximity to the building;
  • Pile foundation on bored or concrete supports. When building in a swamp, such a construction of a foundation block is often the only correct and reliable option if the soil gets wet to the point of a watery porridge. In this case, the piles are driven to the level of hard layers under the bottom of the swamp;
  • A floating or slab foundation can be used on very viscous and dense soils in the absence of flooding and rainwater.

When choosing a specific scheme, it is advisable to perform full deep drainage and drying of a small area of ​​soil of several square meters. By digging a hole one and a half meters deep, you can try to get an idea of ​​the soil of the swamp on which you plan to build a house.

Which foundation in a swamp will be most effective?

The main problem in the construction of any buildings is not the technical or technological issues of arranging foundation systems in areas where swampy soil dominates, but the huge costs associated with a large amount of additional work and the need to ensure effective drainage from the basement parts of the foundation. A strip foundation may seem like the cheapest option, but not every swamp can build one.

Strip foundation for a house in a swamp

The construction of a foundation in the form of a strip in terms of the volume of materials used and the amount of work will be the cheapest from the list above. If the results of a study of soil geology show the presence of coarse-grained sand layers up to one and a half meters deep, it is quite possible to get by with the construction of a classic strip foundation. Most often, this situation arises if the owners of the future building choose an area for construction in the floodplain of a river, in a lowland, where swampy and waterlogged soil is associated with the presence of a river.

The construction of a strip foundation in such a swamp is possible only if the following measures are taken:

  • The site must be equipped with a very powerful drainage system using hydraulic barriers to prevent the penetration of water from nearby areas;
  • The foundation for a house on the site is installed in the highest place, taking into account the possible direction of rain flow;
  • Highly efficient drainage system for soil adjacent to the foundation.

Before starting work on building a foundation in a swamp, it is very important to make sure that there are no underground springs, of which, as a rule, there may be a lot in such an area. If reconnaissance confirms their presence, it is better to abandon the use of this type of structure in the swamp in favor of other options.

Pile foundation in a swamp - the optimal solution for heavy houses

If you are planning to build a solid brick house with an attic, you will need to use foundation systems with maximum load-bearing capacity. For a swamp, this is the pile version of the foundation. The essence of the design of such a foundation in a swamp is to install the required number of concrete or bored piles resting on solid layers of rocky soil under the bottom of the swamp. The cost of such a foundation block for a swamp will be many times higher than the previous option. Unlike strip schemes, which can support relatively small frame-type houses in a swamp, a pile version of the foundation for a house in a swamp can easily support a brick building of several floors for many years.

In this case, to build the foundation you will have to use special equipment with which you can drill and fill bored piles. Doing this amount of work manually is quite difficult. The depth to which the pile support is installed can reach 5-7 meters, which is determined by the geology of the swamp.

If hard soil layers are located at a relatively shallow depth of 2-3 meters, screw piles can be used. They are much cheaper, and in some cases you can even install them yourself. As a preventive measure, the top layers of soil to a depth of 60-70 cm are often removed, road geotextiles are laid and backfilled with a sand-crushed stone mixture. The upper heads of the piles are connected by a powerful grillage or a steel frame made of paired channels No. 200.

If the swampy area has a top layer of hard soil, which is often found on peat bogs and lake remains, it makes sense to use a slab foundation, as it is simpler and easier to make with your own hands.

Slab foundation for a small house

The advantages of a foundation system in the form of a continuous monolithic slab include enormous rigidity and strength. Such a foundation structure will not float up and will not tilt, even if the water level of the swamp rises. A good slab foundation is suitable for frame, aerated concrete, foam concrete houses that require special measures to ensure frame rigidity.

The cost of building a slab foundation in a swamp will cost you 20-25% less than the pile version. If we compare the construction of a foundation system on pile supports and a slab version in ordinary dry soil conditions, then the cost of the slab will be as much as 40% more than the pile system.

The slab construction technology will require digging a pit 60-70 cm deep, filling it with a layer of sand and a layer of crushed stone, laying film waterproofing and installing panel formwork around the perimeter of the pit. For a slab foundation structure in a swamp, in addition to high-quality waterproofing, it will be necessary to lay more powerful steel reinforcement. Most often, reinforcement with 12 mm rods is used with the installation of lintels and crossbars. The base and top of the slab must be insulated with expanded polystyrene or foam glass.

Conclusion

If you do not know the exact geology of the swamp area on which you are going to build a building, choose a slab foundation option. With lower construction costs compared to pile construction, it can be done practically with your own hands, and, most importantly, it will not present you with surprises in the form of pushing out or failure of piles in the liquid soil of the swamp.

  • Do-it-yourself foundation for a house made of aerated concrete
  • Foundation for a wooden house
  • How to insulate a foundation
  • Foundation insulation with polystyrene foam

A house can be built in any area. It is good if there is stable soil and the installation of the foundation can be carried out according to the usual standard norms and requirements. Another thing is unstable, swampy soils. This requires additional costs not only for equipment, but also for proper design, taking into account the specifics of the construction site. Swampy areas are not the most suitable basis for construction. But even here, subject to all norms and requirements, it is possible to build a high-quality, strong foundation that will serve as a reliable foundation for the house for many years. The main requirement is the correct technology for building foundations on unstable, wet soil. The article describes in detail what kind of foundation to choose for a foundation on swampy soil when planning construction in such a problematic place.

Types of foundations and their pros and cons

Swampy soil is a difficult base for a foundation. In this case, two types of foundations can be used: pile and slab. A pile foundation is reinforced with metal or concrete piles; a slab foundation is made in the form of a monolithic reinforced concrete slab, which is poured onto a sand-granite bed.

Slab

A slab foundation is designed to ensure that the load of the building is uniform across the entire base of the slab. Such a base can withstand increased loads and is used not only in individual, but also in industrial construction.

Slab technology is applicable on heavily swampy soils, unevenly compressed soils, and with a high groundwater supply. However, the disadvantage of such a foundation is that it is inappropriate to install it on slopes. If there is even a slight slope, the slab can “slide”. The special advantages of a slab foundation include its high load-bearing capacity. The only drawback here is the increased consumption of materials, which is a very painful fact for individual construction.

To pour such a foundation, you will need many times more reinforcement and concrete than when installing a foundation on solid soils, which, naturally, will entail an increase in the entire final cost of the building.

Pile

Installing a pile foundation in swampy areas is more reasonable and has its advantage in the direction of uneven terrain. Piles can be placed in any hard-to-reach place, on slopes, on any technically difficult soil. Among the advantages of a foundation on piles is not only its installation in hard-to-reach areas with complex terrain and unstable soil, but the advantage is the speed of installation of piles and an affordable price.

The opinion that a pile foundation is more suitable for small, lightweight structures is incorrect. By increasing the number of supports, the highest possible bearing capacity of the foundation is achieved, which is in no way inferior to the parameters of the slab base. However, at the same time, the costs of such a foundation will increase and its cost will be equal to that of a slab foundation. When constructing reinforced, heavy structures, this fact should always be taken into account when it comes to the cost-effectiveness of a pile foundation.

Preparatory stage

At the first stage of construction, a full soil study is carried out. For this, a hand-held probe can be used to take soil samples. This method is used in the construction of light wooden buildings and structures.

The probe is lowered into a well 5 m deep. During the capital construction of stone or brick houses, serious geological exploration is required. In this case, the depth of measurements is 8-10 m. Wells for measurements are located in the corners of the future structure. There must be at least four such measurements (wells). Determine indicators of soil composition and depth of its layers; level, quantity and composition of groundwater. One more indicator is needed - this is the freezing point of the soil.

The upper layers of marshy soil are mainly peat. Clay and sandstone may follow. Peat is a porous, completely loose material with low compression resistance and increased instability. If the layer thickness is small, the peat is removed and the foundation is placed on the lower hard rocks. This is a shallow foundation. Its peculiarity is that the slab under the foundation is located above the freezing point of the soil. This base is suitable for light buildings.

A shallow foundation is arranged so that it can rise and fall slightly during heaving processes occurring in the soil. Thanks to this, it does not crack and retains its shape. This base is not used for brick and stone houses. If the peat layer on the construction site is deep enough (more than 5 meters), it is necessary to strengthen the foundation with piles.

Not only the peat layer is a problem when building a foundation on swampy soil. The second problem is the nearby groundwater. There are two ways to combat this problem:

  • lower the water level;
  • raise the area.

The installation of a drainage system helps to significantly reduce the groundwater level. To drain water from the construction site, trenches are dug to a depth of about two meters, and the entire drainage system is led to drainage wells. A layer of crushed stone is poured into the trench and drainage pipes are laid on it. Drained water from wells is pumped out using submersible pumps.

To raise the site, you need to make an embankment of stone and sand. To do this, remove the top, weak layer of soil and fill the area with a layer of stone and sand. Such an embankment is carefully compacted and compacted with rollers.

Slab foundation installation technology

The slab foundation must be made in accordance with all standards according to the following basic scheme:

  1. Removing the soil layer. Depth 1 m.
  2. Making a mound (pillow) from a mixture of gravel, stone and sand. The embankment is compacted and concrete preparation is done.
  3. Covering with waterproofing and thermal insulation.
  4. Making a frame from reinforcement. Tying the frame with wooden blind areas.
  5. Pouring concrete over the frame and its subsequent compaction with an industrial vibrator.
  6. Leveling the surface as a rule.

Slab foundation installation diagram

Installation of a pile foundation

The main thing here is the piles. They can only be reinforced concrete or combined. There are three types of piles:

  • screw metal;
  • driven reinforced concrete;
  • bored

Bored piles with asbestos-cement formwork are installed only when draining the supporting soil layer. They have fairly good load-bearing capacity. Screw metal piles are somewhat inferior in their load-bearing characteristics to bored piles, but they have high installation qualities: speed and ease of installation, ease of transportation.

Scheme of a bored pile foundation

A distinctive feature of screw supports is the ability to extend them to the required length. Driven piles are installed using pile driving equipment. At the same time, it is not always possible to use heavy equipment in individual construction.

The main criteria when calculating the number of support piles are the type and magnitude of the load. Regardless of the type, piles can be installed in the following order:

  1. Rows under the walls.
  2. Alone under a support.
  3. Bushes under the columns.
  4. Fields under strong vertical loads.

All calculations of the length and volume of piles are performed based on geological survey data in accordance with construction standards and regulations. The lower ends of the piles should rest on dense soil. It should be noted that on each of the foundations considered, any residential building in a swampy area can be installed. Any of the construction technologies is suitable for building a house; restrictions can only be related to the operating conditions of the building being constructed.

In conclusion, it should be noted that not all building materials are suitable for buildings in wet areas. For example, at high humidity it is not recommended to use foam concrete, expanded clay concrete, or aerated concrete due to the strong hygroscopicity of the material. Timber is also not the best material. On swampy areas, it is best to build brick, stone or frame houses. But the most important thing is to lay the foundation correctly and absolutely accurately. To a greater extent, it is precisely because of this that a house built according to all the rules will last a long time and reliably.

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Never drying out swampy soil with moisture-loving vegetation that can be systematically moistened is not the most favorable place to build a house frame. The close location of groundwater creates seasonal fluctuations in soil, especially during spring warming. Modern construction technologies can solve the problem of how to organize a foundation in a swamp so that it can withstand the load of a house.

Soil analysis

What does swampy land represent? This is an area with a porous structure, which is 90% water. The remaining percentage is formed by chaotically located particles of minerals - peat, sand, clay. The unsystematic order of occurrence of rocks does not allow calculating the load on the soil.
Soil studies on the site will help identify the following characteristics of the area:

  • type of soil mass;
  • groundwater volume;
  • freezing depth;
  • distance of the aquifer from the surface.

The data obtained make it possible to determine the physical properties of the layers, their thickness and depth, and to characterize changes in the soil over the past few years. Based on geological expertise, you can choose which foundation to build in marshy areas.

How to explore the soil yourself?

It is not advisable for summer residents to delve into the details of geodetic surveys. Private developers need to take a number of simple measures:

  • selection of earthen material from four wells. The drilling depth is 5 m for wooden structures, 8 m for large stone buildings. It is better to probe the surface in the spring, when it contains the maximum amount of moisture.
  • Mechanical analysis is carried out by taking a small piece of earth. It rolls out in your hands and bends into a ring. A disintegrated element indicates sandstone, an unstable element indicates loam, a dense element indicates clay;
  • inspection of vegetation. On excessively moist marshy soils, wild rosemary, blueberries, sedge, cloudberries, horsetail and other crops are present.

Research and determination of soil type include determining changes in groundwater level.

When does the groundwater level change in a swamp?

The volume of groundwater varies throughout the year. During the thaw period, their number increases significantly. The lowest groundwater level was recorded in winter. A high aquifer imposes restrictions on building a frame in a swampy area. A moisture concentration of 2 meters or less poses a threat of flooding of trenches, pits, and the appearance of mold in the house or basement. A clear operating algorithm will help minimize the impact of springs on the life of the foundation.

Pile frame

A base designed for wetlands. Supporting elements are piles that are driven into the soil. A pile foundation in a swamp allows you to solve the problem of heaving, instability of the top layer of the earth, and allows you to smooth out the unevenness and slope of the territory.
Advantages of the structure:

  • low-cost, non-labor-intensive process (in 2 days you can build a supporting structure);
  • mounting the frame reduces the amount of earthwork: garbage removal, digging a pit, concreting;
  • the ability to choose building materials for piles: wood, steel, reinforced concrete;
  • increased strength, long service life.

It is rational to use a pile foundation in swampy, unstable terrain with a high groundwater level. There are several limitations to consider when choosing a support structure:

  • weak bearing capacity in horizontally moving soil;
  • additional financial costs for the arrangement of the basement (filling voids).

The average depth of a well pit is 10-15 m. To mount a pile frame at a high groundwater level, use pillars at least 25 m long. The piles must be driven in until they fit tightly to the ground.

Work algorithm for constructing a foundation on piles

Construction work is permissible at any time of the year.

  1. We treat the tongues with an antiseptic to prevent the development of corrosion.
  2. We plunge the piles into the ground: we screw in the driven ones, and for the screw ones we use a special lever.
  3. Cut off the excess protruding part.
  4. We fill hollow pipes with cement.
  5. Using an electric welding machine, we mount the support platforms on the cut parts of the piles.
  6. We treat the surface with a waterproofing solution.
  7. We connect the structure along the heads with a horizontal grillage.

High speed of construction and resistance to soil vibrations make it possible to increase the service life of the structure.

Slab foundation

The structure is widely used for the construction of a monolithic stone building. Concrete slabs are resistant to temperature changes and loads.
The problem of high groundwater levels is solved with the help of a sand and gravel cushion located at the base of a monolithic slab, buried to the level of soil freezing. Rocks allow spring flows below their location, which prevents deformation. The sequence of technological steps will allow you to create a solid slab foundation in the swamp.

  1. We prepare the wetland, clear it of vegetation and debris.
  2. We drill holes in the corners of the future structure.
  3. We drain the trench. For groundwater levels up to 2 meters from the surface, use pumps; from 2 meters and below, limit yourself to the drainage system.
  4. We will strengthen the bottom of the pit with an embankment of sand and gravel. This will protect the foundation from the effects of groundwater. We form roofing felt flooring on top.
  5. We make formwork from lumber.
  6. We install reinforcement made of metal rods along the entire perimeter of the form-building structure.
  7. We fill the trenches with concrete mixture in several approaches. The thickness of each layer should not exceed 0.2 m.
  8. Dismantle the concrete form after the solution has dried (it will take several days).
  9. We treat the vertical and horizontal surfaces of the frame with waterproofing mastic.

A foundation in a swamp made of monolithic slabs is an expensive type of construction. Changes in soil heaving will not affect the reliability and strength of the frame. Therefore, slab foundations are mainly used for marshy areas.

Tape base

A shallow foundation for a house is suitable for the construction of small frame structures made of wood. The peculiarity of the type of supporting structure is that the depth of the masonry is higher than the freezing level of the soil. When arranging the feed, you need to take into account a number of nuances:

  • The role of the drainage system is performed by a cushion of sand and gravel.
  • When the soil heaves, the reinforced frame rises slightly, but the use of monolithic technology allows it to maintain its shape and prevent the appearance of cracks.
  • At the design stage, soil characteristics should be determined. This will allow you to calculate the effect of loads on the future construction and determine the safety margin.
  • The sequence and technique of performing the work of arranging a foundation, which is located in a swampy area and is relevant in case of high groundwater loss, is identical to laying a deep-depth tape - digging a pit, forming a cushion, constructing formwork, reinforcement and layer-by-layer pouring of cement mortar.
  • It is advisable to install a channel for water drainage along the entire perimeter of the foundation at a distance of 1.5 - 3.00 m.

Ease of installation and low cost make the tape popular as a foundation on marshy soil.
Dampness and moisture have a destructive effect on the frame. It is difficult to predict how soil density will change over time. To avoid the effects of swelling of the ground, use waterproofing systems. When choosing the type of foundation that will be located in soft, swampy terrain, focus on the climatic conditions of the area, the type of structure and the budget.

A reliable and solid foundation on marshy soil is a very complex and difficult task. The entire complexity of construction in swamps is determined by the bearing capacity of the soil. Swampy soil is prone to deformation. If during construction the soil had the required density, then over time everything can change. Swampy soil is especially dangerous in winter. The moisture in it freezes, and the earth swells in the immediate vicinity of the foundation. In addition, dampness and moisture have a destructive effect on the foundation. So what measures should be taken?

Before starting the construction of a foundation on swampy soil, the geological situation on the site should be carried out.

What kind of foundation is needed?

One of the most expensive stages of construction is, especially on swampy soil. The groundwater in these areas is very high, and there is a risk of flooding in spring and winter. To avoid such problems, before starting foundation construction, you should think about installing drainage, which is needed to drain excess water. Before choosing the desired type of foundation, area, and depth at which it can be laid, it is necessary to study the geology of the construction site. Well-proven types of foundations in swampy areas include:

  • slab base;
  • pile foundation;
  • shallow foundation.

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How to pour a foundation slab with your own hands?

Scheme of the foundation - slab structure.

For work you will need:

  • shovels (bayonet and shovel);
  • hammer and nails;
  • roulette;
  • automixer;
  • saw;
  • Bulgarian;
  • sand;
  • water;
  • gravel;
  • wooden boards;
  • reinforcement Ø 10-12 mm;
  • film;
  • concrete M200.

People living in northern latitudes are of the opinion that only a monolithic slab with reinforcement is suitable for a foundation on swampy soil. The pleasure is quite expensive, but the reliability is worth it. Before laying such a foundation, the soil layer should be removed to a depth of 1 m. Then a cushion consisting of sand and gravel is made. It needs to be compacted very well. Such actions will slightly raise the platform under the foundation.

If the cushion is laid correctly and efficiently, then groundwater will flow freely under the base, the effect of heaving during severe frosts will be significantly reduced, and the pressure of the structure on the soil will be distributed evenly.

Scheme of a columnar foundation.1 – horizontal waterproofing; 2 – grillages, 3 – sand cushion.

The foundation cushion does not retain moisture inside. Additional stability of the house is gained due to the non-buried structure.

After this, you can begin the actual construction of the foundation slab. Before you begin to reinforce the slab, the pillow is covered with roofing felt in several layers. Ruberoid will prevent moisture from penetrating into the concrete and will not allow the concrete “milk” to leak out. Reinforcement of the slab is performed both from below and from above. After this, concrete is poured, and vibration is a prerequisite (it gives the concrete additional strength).

The shape and dimensions of the slab must correspond to the design of the future building. The lower part of the base must be equipped with stiffeners. Thickenings that have a smaller height are made both in longitudinal and cross sections (steps up to 1.5 m).

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Construction of a pile foundation

Required tool:

  • building level;
  • shovels;
  • sledgehammer and hammer;
  • Bulgarian.

The pile-type foundation was developed specifically for swampy areas, but construction is expensive. The work almost always requires complex work, engineering surveys and the rental of special equipment.

But in this case, the end justifies the means, because the piles will perfectly protect the structure from negative external factors. Using special equipment or a sledgehammer, the structural elements are driven into the soil to the required depth. Bored piles are sometimes used. They are shaped like large screws or self-tapping screws. When using them, you don’t need to hammer anything in, you just have to screw it in.

The piles themselves are quite long, due to which they cross dangerous soil zones and enter layers that have a much greater load-bearing capacity. It turns out that the pile will rest on a reliable foundation. In rare cases, wooden piles are used, but this is not recommended by professionals (wood does not tolerate exposure to water).

The best option for constructing a foundation on marshy soil would be to use reinforced concrete piles. Products made in accordance with all norms and rules can last a very long time. Naturally, there are limitations in service life, but the swamp would rather dry out than concrete made according to modern standards would collapse.

After driving the piles, they begin. Usually for swampy areas it is made in the form of a reinforced concrete slab with holes pre-drilled for pile elements. The presence of a grillage is necessary to distribute the loads exerted on the foundation by the weight of the building. The next step is the construction of wall structures, floors, roofs and other components of the structure. It should be remembered here that the foundation can be loaded with walls only when the concrete has gained the necessary strength. This will happen after 2-3 weeks.