Insulating the foundation from the outside is necessary work to ensure the preservation of heat in the room, protection from moisture, and saving energy resources.

The optimal solution is to carry out all the manipulations during the construction of the building, but it is possible to implement the plan after the construction of the building is completed.

For each individual case, we have developed our own most convenient algorithm, according to which the foundation of a private house should be insulated from the outside, and materials have been selected that allow us to achieve the highest quality and most effective insulation of the foundation.

Variety of materials for thermal insulation

Insulation of the foundation base from the outside is carried out:

Each of the listed materials is ideal for providing high-quality insulation of the foundation of a house from the outside.

In all cases, it should be remembered that thermal insulation of the foundation is not necessary in order to increase the flow of warm air entering the room. Every effort should be made to prevent the cold from penetrating into the building.

The insulation must be moisture resistant

If they want to avoid material costs and save as much as possible on arranging a warm foundation for a house, many owners of private buildings carry out all the work using the ground. The backfill method allows you to achieve a positive result, but modern materials guarantee that a reliable and high-quality warm foundation will be created.

When deciding how to insulate the foundation, you must first choose the method of performing the work, because the thermal insulation material can be fixed on the outside of the building or on the inner surface of the base.

Depending on which insulation was chosen and on the method of insulation, materials for insulating the foundation necessary to achieve the goal are selected.

You can purchase everything you need if you know how to properly insulate the foundation of a residential building in order to provide the owners with comfortable living conditions. The materials used should not be deformed under the influence of aggressive environments or allow moisture to pass through. They must be characterized by a long service life, resistance to temperature changes, low weight, strength and high density.

Taking into account all the requirements, experts recommend using the following as insulation:

• penoplex;
• extruded polystyrene foam;
• sprayed polyurethane foam.

Before insulating the foundation of a house from the outside with your own hands, it is necessary, in strict accordance with all requirements, to prepare the base surface on which the thermal insulation material will later be fixed.

To spray polyurethane foam you will have to invite professionals with equipment

Spraying polyurethane foam requires the participation of craftsmen and the use of special equipment; in addition, such a coating is resistant to exposure to ultraviolet rays.

That is why owners of country buildings strive to insulate the foundation of a private house using penoplex, which is cheaper, but quite durable and of high quality.

Insulating the outside of a house with polystyrene foam is also popular because it does not require the use of special fasteners. To securely fix it, it is enough to use an adhesive composition similar to polyurethane foam. This is foam cement.

Execution of work

Knowing how to insulate a foundation from the outside, you can correctly select the most suitable material and prepare the foundation.

This stage requires special attention, since the algorithm for performing the work depends on the features of the constructed frame. In cases where we are talking about piles or pillars, then the construction of a brick wall will be required to fill the gaps between already installed piles or pillars:

1. You will have to dig a trench around the entire perimeter of the house and place a sand cushion at the bottom, which will need to be thoroughly compacted.
2. The second stage is laying the reinforcing mesh, on top of which the concrete base is poured.
3. After 10 days, the concrete will gain strength and laying can begin.

Another option that is considered when deciding what and how to make a warm foundation is to use slag or expanded clay. Having decided how to insulate the foundation of the house, you can begin making calculations and purchasing materials.

Surface preparation begins with sealing all detected defects on the outer surface of the foundation base of an already constructed building.

For this purpose, you can use a sand-based plaster mixture, and the largest cracks can be filled with polyurethane foam. Primer is applied on top of the plaster. This should be a deep-penetrating composition that ensures high-quality adhesion of materials. For more information about insulating the base, watch this video:

Having made the final decision on how to insulate the foundation from the outside, you need to take care of arranging high-quality waterproofing. To treat the foundation from the outside, coating materials such as bitumen mastic are needed.

From the outside, the foundation is insulated in two layers

Now it's time to attach the first layer of polystyrene foam. It is necessary to apply an adhesive composition to it and press it tightly to the surface that is being insulated.

All seams and joints are foamed and after the foam has hardened, it is cut off and the entire covered area is covered with reinforcing mesh to create a second layer of plaster.

To insulate the foundation from the outside, two layers of polystyrene foam are required. The final decoration will be:

• slabs;
• panels;
• plaster and paint;
• tile.

Before choosing the best way to insulate the foundation of a built house, you need to decide what and how to insulate the area underneath it. To do this, you should know how to insulate the foundation, given that much depends on the quality of the floor. Penetration of cold air is possible from the underground or basement. Treatment of old floors, during which it is good to use modern insulating materials. For more information about the stages of work, watch this video:

By considering various methods and options for foundation insulation, you can see that this process is not as simple as it might seem.

Failure to comply with the nuances of the technological process causes disruption of the microclimate in the room, heat loss, and unjustified energy costs.

However, knowledge of the features of each individual structure and the building materials used for its construction will help to achieve success. So, for example, a concrete base is insulated only from the outside, because practically no cold air passes through it, but the false base of a pile foundation requires mandatory insulation of the inner surface.

Every person who owns a private house or cottage or dacha faces the problem of heat loss, especially in winter. Approximately 1/5 of heat loss occurs through the foundation, and it is this foundation that is often forgotten to be insulated, especially in houses that do not have a basement. However, it is necessary to insulate the foundation, since this can significantly reduce heat loss, reduce humidity in the basement and extend the life of the structure as a whole. So how to insulate the foundation of a house from the outside? This will be discussed further.

There are several reasons that indicate that it is simply necessary to insulate the foundation:

• A common mistake made by building owners is to insulate the basement from the inside, not the outside, while the foundation itself is not protected from the harmful effects of moisture on it. Thus, under the influence of moisture, cracks form in the foundation at low temperatures, which over time can lead to partial or complete destruction of the foundation. That is why it is necessary to do insulation not inside, but outside the foundation.
• External insulation of the base also allows not only protection from high humidity, but also makes it possible to prevent freezing of the foundation in winter. When thermal insulation is performed correctly, insulation can reduce the impact of moisture on the foundation, since it is much more resistant to it.

Methods for insulating the foundation from the outside

How to insulate the foundation of a house from the outside with your own hands? Today, the building materials market offers a wide selection of insulation materials. The most commonly used insulation methods are:

• The classic and ancient method is to insulate the foundation with gravel, expanded clay or sand.
• Using sheet insulation (for example, polystyrene foam).
• Use of sprayed material (eg polyurethane foam).

Each of the materials has its own advantages and disadvantages, which will be discussed further.

This type of insulation for the foundation of a house is most often used in private construction, since polystyrene foam has the following advantages:

• The material has high strength and durability.
• Has high moisture resistance.
• The material is quite easy to install and secure to the base, which allows you to do the finishing yourself.
• Expanded polystyrene is inedible for rodents and is resistant to damage.
• Carrying out external decorative finishing is not particularly difficult.
• The cost of the material is affordable for almost everyone.

As for the technology of finishing the foundation from the outside, it is as follows:

• It is necessary to insulate the foundation of the house from the outside immediately after it has been erected and the rough floor of the first floor has been completed. However, it is also possible to insulate the foundation of an already finished house, but to do this you need to dig a trench around the foundation at least 1 m wide and with a depth equal to the depth of the foundation.
• Before proceeding with insulation, the foundation walls must be cleaned of all contaminants.
• If the groundwater level is elevated at the construction site, a drainage system must be installed. To do this, a layer of sand is poured into the bottom of the trench, a layer of geotextile is laid, then perforated pipes with a diameter of about 10 cm into which gravel is poured. The pipes are also wrapped in geotextile and covered with sand. They need to be taken to a special collector well.
• The next step is to coat the foundation walls with a latex-based primer. This primer will allow you to completely fill all the cracks and small cracks in the foundation, and will also ensure good adhesion to the waterproofing material.
• Then they make waterproofing (usually self-adhesive), which is smoothed with a roller, and the joints are sealed with a special sealant.
• Now you can start laying the insulation. It is fixed to the walls using special glue, which is applied to the polystyrene foam in a small strip at a distance of 1-2 cm from the edge of the sheet, as well as in small dots along the entire perimeter.
• Thus, continue along the entire perimeter of the foundation. If the foundation is high and one row of polystyrene foam is not enough, then the insulation is laid in a checkerboard pattern, like a brick, in several rows.
• Once all walls are insulated, large gaps are sealed with foam or sealant.
• Where the foundation will subsequently be covered with sand, there is no need to further strengthen the polystyrene foam, but on the protruding part it is secured using special dowels.
• Next, the insulation must be plastered, and a reinforcing mesh must be used to give strength (it must be buried in a layer of plaster).

Thus, by doing everything correctly, you can achieve high-quality insulation without leaving cold bridges. In addition, this finishing gives the house a full, complete look.

This method of foundation insulation differs from the previous one in that it does not need to be fixed; it is applied directly to the foundation walls using a special sprayer. Polyurethane foam is sprayed onto the surface of the foundation in liquid form, after which it hardens directly on the walls for some time. This finishing method allows you to avoid insulation joints and also ensures a tight fit to the walls.

According to the application technology, polyurethane foam can be applied to the wall without any effort, and there is no need to additionally prepare the surface (i.e., no need to cover it with a primer, treat it with glue, etc.), just clean it of dirt.

Usually the insulation layer is about 5 cm, and rarely more. This layer allows for high-quality insulation. It should also be noted that polyurethane foam is resistant to moisture, which indicates additional waterproofing of the foundation.

It must also be said that such material can only be applied using special installations with sprayers, so doing it yourself is practically impossible.

This method of insulating the foundation from the outside has been proven for decades. In fact, expanded clay is a porous material that is quite light in weight and has good thermal insulation properties. However, this method is not advisable to use if in an area with a sufficiently high groundwater level, since the material is hygroscopic, that is, it easily absorbs excess moisture.

In order to reduce the hygroscopicity of the material, it is necessary to shield expanded clay from the external environment using waterproofing materials.

Expanded clay insulation technology is as follows:

• Along the entire perimeter of the foundation along its walls, it is necessary to dig trenches, the depth of which is slightly greater than the freezing level of the soil.
• Next, the walls of the trench must be waterproofed using any waterproofing.
• After this, the trenches are filled with expanded clay, and a blind area is made on top of it.

The blind area is performed as follows:

• They install formwork from planed boards, just like for the foundation. The width of the blind area is usually at least 60 cm.
• To strengthen the blind area, reinforcing mesh is laid on top of the expanded clay.
• Next, the concrete solution is poured.
• After some time, when the blind area has gained strength, the formwork is dismantled.

Thus, to summarize, we can safely say that the most rational material for insulating the foundation is expanded polystyrene, which is popularly called polystyrene foam. It is budget-friendly and of high quality, and also allows you to perform insulation yourself, without the involvement of specialists. However, how and with what to insulate the foundation of a house from the outside is up to the owners of the house to decide.

Insulation of the foundation of a wooden house

Many owners of wooden houses are faced with the fact that in winter the floor freezes on the 1st floor. This phenomenon can only be eliminated in one way - to insulate the foundation of a wooden house from the outside. The foundation of a wooden house is built from different materials. The method of insulating the foundation of a wooden house depends on the type of supporting structure of the building. Modern thermal insulation materials are used to insulate the foundation of the house. This article presents options for insulating foundations of various designs.

The foundation of a wooden house is a supporting structure that is in direct contact with the natural foundation and the structure itself. In addition to its supporting function, the foundation protects housing from the negative influences of the soil. It is important that the base of a wooden house does not cause heat leakage from the home.

The foundation of the house is constantly exposed to moisture penetration from the soil and changes in ambient temperature. In winter, moisture that gets into the body of the base of the structure freezes and destroys the supporting mass. The cold begins to penetrate into the home through cracks. As a result, the floors in the house will always be cold in winter. That is why it is necessary to insulate the base of a wooden house.

It is impossible to insulate an old foundation from below, but its walls are quite accessible for thermal insulation. Since supporting structures can be of different types, the thermal insulation of the foundation from the outside is carried out in different ways.

Materials for foundation insulation

Insulation of the foundation must be done at the stage of its construction. Although there are circumstances when careless builders did not take care of this in due time. And now the owners of the house have to re-insulate the base of the wooden house.

The time comes, and homeowners think about which insulation to choose. Among the wide variety of heat-insulating agents, it is necessary to highlight materials suitable for insulating foundations:

• expanded polystyrene;
• polyurethane foam;
• expanded clay;
• Styrofoam.

All these materials have low thermal conductivity and high resistance to temperature changes.

Expanded polystyrene

Penoplex (expanded polystyrene) slabs

This material has high thermal insulation properties, moisture resistance and insusceptibility to low temperatures. Thanks to these qualities, extruded polystyrene foam has gained great popularity as external insulation for the foundations of wooden houses. Expanded polystyrene is convenient for insulating strip foundations and plinths.

The material has a fine-cell structure. It is produced by exposing polymer granules to high temperature and pressure in carbon dioxide. Insulation comes on sale in the form of a slab material called penoplex. The service life of polystyrene is about 40 years.

Manufacturers often call expanded polystyrene boards penoplex. Penoplex with a thickness of 50 mm corresponds in heat-shielding properties to 75 mm of foam plastic and 95 mm of mineral wool.

Video on insulating the foundation with penoplex:

Polyurethane foam

The polymer is sprayed onto the foundation walls using special equipment. Once on the treated surface, polyurethane foam greatly increases in volume. In terms of its thermal insulation properties, a 50 mm layer of polymer is similar to a 120 mm thick sheet of expanded polystyrene.

Insulation of the foundation with polyurethane foam

The hardened foam on the walls of the base of the building forms a seamless, dense coating. Unlike sheet insulation, the sprayed outer coating does not require additional sealing of the seams. In addition, the polymer has high adhesion and “sticks” to almost any surface.

Expanded clay

Expanded clay granules are produced by firing a foamed clay solution. Expanded clay has high thermal insulation qualities. This is one of the cheapest thermal insulation building materials.

Lining the external walls of the foundation with expanded clay prevents the base of a wooden house from freezing, even in the conditions of the Far North. The only drawback of the material is its low commercial availability.

Styrofoam

Polystyrene foam is essentially the same polystyrene foam, but has not been extruded (pressure treated at high temperatures). Foam boards are used to insulate the foundation and basement of a house. To prevent heat leakage from a wooden house from below, foam plastic with a thickness of 40 to 120 mm is used.

Polymer boards are easy to process. Most often they are attached to the foundation walls using bitumen mastic. Foam plastic is also fixed to the wall with dowels - fungi.

Polystyrene foam, along with its high thermal insulation qualities, is a very fragile material, so the outside walls of the foundation lined with foam plastic necessarily need a final protective coating.

Methods for insulating the foundation of a wooden house

Mostly wooden houses are built on strip, column and pile foundations. In each case, it is necessary to cover the base and basement of the house with insulation.

Strip foundation

This type of foundation can be made monolithic or constructed from prefabricated reinforced concrete blocks. Also, the support strip under a wooden house is made of rubble stone or flagstone.

The technology for how to insulate the foundation of a wooden house from the outside with your own hands is as follows:

1. A trench is dug along the perimeter of a wooden house to the depth of soil freezing.
2. The foundation walls are cleaned of soil residues and covered with bitumen mastic.
3. The insulation boards are installed on a vertical surface, heating the bitumen waterproofing layer with a burner.
4. A reinforcing metal or polymer mesh is fixed to the insulation.
5. All surfaces are primed, puttied and plastered.
6. Insulation is laid on the sandy cushion of the blind area.
7. The blind area is concreted, asphalted, lined with ceramics or stone.

Insulation scheme for a strip foundation of a wooden house

The concrete monolith of the house support strip with a thickness of 40 - 50 cm does not need insulation. The physical characteristics of such a reinforced concrete mass have sufficient heat-insulating properties.

Columnar foundation

As a matter of fact, it makes no sense to insulate the columnar foundation itself. The main heat leakage occurs through the space between the bottom of a wooden house and the ground. The constant movement of air masses underground creates an outflow of heat from the lower floor of the building.

To prevent this negative phenomenon, the outer perimeter of the underground is covered with vertical fences. Fences can be made from a variety of materials: from wooden panels to reinforced concrete slabs. Enclose the base with siding (thin-sheet metal or polymer panels). Siding performs a purely enclosing function.

Due to the enclosed space, drafts stop and the underground air temperature stabilizes in the positive range, and this ultimately leads to effective insulation of a wooden house.

The basement fence is erected from brick, wild stone or other masonry material. It is important that the masonry of the fence is not rigidly connected to the columnar supports. Due to various geological movements, the pillars can move the masonry of the fence. In this case, the wall of the base may crack and collapse.

A hermetically sealed space inside the base can lead to increased air humidity. This in turn will create a favorable environment for the growth of fungi and mold. To prevent the air in the underground from stagnating, it is imperative to make vents in the basement enclosure - small openings that provide natural ventilation for the underground.

For greater reliability of thermal insulation of the base of the house, polyurethane foam is sprayed onto the internal surfaces of the fence.

Pile foundation

The principle of insulating the pile foundation of a wooden house is the same as in the previous case. The house, located on stilts, also has an open underground, which must be closed from the outside environment.

Wooden houses are supported on both wooden and reinforced concrete and screw piles. To insulate the basement of a house on a pile foundation, wooden panels, polymer or metal siding are most often used.

Features of foundation insulation with expanded clay

The method of insulating the foundation with expanded clay has its own characteristics. Since, unlike slab insulation, expanded clay is a bulk material, they do it this way:

• a trench around a wooden house is made 20 - 30 cm wide; the depth of the ditch is made just below the soil freezing mark;
• sand 10 cm thick is poured onto the bottom of the trench; then make a layer of crushed stone or gravel of the same thickness;
• sheets of roofing material are attached to the walls along the outer perimeter of the trench;
• the ditch is filled with expanded clay; pour the granules in layers of 30-40 cm; each layer is compacted;
• the top of the insulation is covered with a cement screed;
• a half-brick thick wall is placed along the screed; masonry is carried out to the height of the building’s base;
• a metal mesh is laid across three rows of bricks, connecting the masonry and the base of the house;
• the space between the masonry and the base is filled with expanded clay;
• a blind area made of cement mortar is installed on top of the masonry; the screed is covered with a galvanized sheet.

Base insulation with expanded clay

If the roof insulation is not done simultaneously with the thermal insulation of the supporting structures of the building, then the thermal insulation of the foundation will not bring the desired result. The heat will go up, the floors and walls in the home will remain cold.

The base of a wooden house must be insulated, since the owners try to eliminate the cold in living quarters by increasing the load on the heating system of the house, and this results in exorbitant financial costs for heating the home. In this regard, it is better to properly insulate the foundation once and live in a warm house for many winters without incurring unnecessary expenses for heating the house.

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Insulating the foundation of a house performs several functions: it not only prevents heat from escaping through the base of the house and reduces heating costs, but also acts as waterproofing and protects the foundation from frost heaving of the soil. Without thermal insulation of the foundation, the first floor of the house will be cold and damp. Practice shows that insulating the foundation of a wooden house from the outside solves all these problems. It is much more effective than insulating only from the inside. In some cases, thermal insulation of the foundation is done both from the inside and outside.

Why is it better to insulate the foundation from the outside?

Experts believe that this option is preferable for several reasons.

It is recommended to insulate the foundation from the inside only if the basement has good ventilation. Otherwise, the humidity in the basement will increase, in addition, the inner layer of insulation shifts the dew point, because of this the entire base is exposed to moisture and cold. This reduces its service life and leads to rapid destruction.

Wooden houses are usually placed on a columnar, pile or strip foundation. These types differ in their design, which means their insulation is done differently.

For thermal insulation of any type of base, extruded polystyrene foam (EPS, penoplex) is used. It is durable, has a long service life, does not emit toxic substances, is resistant to compression loads, does not allow water to pass through, and does not grow mold or moss. It is easy to use, attached to the foundation with special glue or with the help of umbrellas; the foam boards have a convenient connection to each other.

Strip foundation

First, they dig a trench all the way to the bottom of the foundation. Its width is 80-100 cm, since the blind area is also insulated at the same time. If the foundation is of a recessed type, then the first 40 cm deep trench is dug to the width of the blind area, and then, to save effort, you can make it 50 cm wide.

If the house was built some time ago, cracks may appear in the concrete. They are covered with a mixture of cement and construction adhesive if the cracks are small. Larger damage is repaired with cement mortar.

The next step is waterproofing. To do this, the surface of the foundation tape is covered with bitumen mastic, onto which roofing material is glued. The sheets are glued overlapping, the seams are additionally coated with mastic. More modern roll materials are also used, such as self-adhesive roll waterproofing.

After this, the insulation is glued. Although penoplex is often attached to dowels, it is still better to give preference to glue or liquid nails - they do not violate the integrity of the sheets. How to insulate a strip foundation with polystyrene foam, watch the video:

The joints between the sheets are foamed with liquid foam.

After installing the insulation, geotextiles are glued onto it. It will reduce the effect of soil heaving on the heat-insulating layer.

Next, the trench is backfilled to the level of the blind area. Sand and small crushed stone are poured under the blind area in a layer of 0.15-0.2 m, and the cushion is thoroughly compacted. This layer will protect the blind area from loads arising from soil movement. A layer of dense insulation is placed on top. The same penoplex is suitable due to its resistance to compression loads. Concrete is poured on top; it can additionally be reinforced with mesh.

Attention! To reduce the effect of frost heaving, the insulation layer is placed at the level of the base of the foundation. The most effective combination of penoplex insulation up to the level of the walls in combination with insulation of the blind area at the level of the sole.

Pile foundation

How to insulate the foundation of a wooden house on stilts? For a pile foundation, as for a columnar foundation, a fence is built - an imitation of a base, closing the space between the piles. This will already reduce heat loss to some extent. For effective thermal insulation of a pile foundation you need:

• arrange a basement,
• insulate it inside and out,
• insulate the floor.

You can build a thin brick wall around the perimeter, or you can use slab materials that are attached to the sheathing. If you choose the option with a brick wall, you need to pour a shallow concrete strip 20 cm thick on which the wall will be built. It is not necessary to use ceramic bricks; you can take foam blocks or foam glass.

Important! The space under the floor should not be sealed. After installing the intake, vents must be made in it - ventilation holes measuring 10-15 cm. They are placed evenly on all sides of the house so that they are opposite each other.

To fasten panels or slabs, a sheathing is made from a metal profile or wooden blocks. For example, DSP can be used as outer cladding. There are already insulated facade panels that perform decorative and thermal insulation functions.

A shallow trench is dug under the casing, into which a layer of sand (2-3 cm) is poured, expanded clay is placed on it, and the trench is covered with earth on top, so that there is no gap between the soil and the casing.

The video shows the structure and insulation of the false base:

To insulate a pile foundation, use

• expanded polystyrene,
• Styrofoam,
• foam glass in blocks,
• liquid penoizol (urea foam).

The first two options are most often used. Foam glass is too expensive for a private home, and liquid foam insulation requires special equipment or the work of specialists, which is also expensive. It’s easier to insulate the foundation of a wooden house with your own hands using polystyrene foam or expanded polystyrene from the outside. The main thing is that the material does not absorb water, so mineral wool will not work here. The foam is glued to the adhesive foam; for reliability, you can use additional wooden planks, which are attached with self-tapping screws to the sheathing through the foam.

Important! It is advisable to attach polystyrene foam or polystyrene foam to the guides, and not between them. In this case, there will be no gaps or cold bridges, since the thermal conductivity of wood, and especially metal, is greater than that of foam plastic.

You can insulate a pile foundation with polystyrene foam or EPS from the outside or the inside. If this is done outside, then the insulation is attached before finishing. If the finishing is already attached to the base, for example, if these are facade panels or DSP boards, then the insulation is mounted from the inside.

Floor insulation

To insulate the floor in a wooden house on a pile foundation, I usually use mineral wool, basalt wool, expanded polystyrene, foam plastic, and liquid insulation.

Thermal insulation is done during the construction and installation of the floor as follows:

1. They make a subfloor on which the insulation will lie.
2. A vapor barrier and windproof layer is first placed on the sheathing.
3. Then they put insulation.
4. Vapor barrier and waterproofing are placed on top.
5. After this, a finishing floor is constructed.

The layer of mineral wool must be at least 10 cm. If it is necessary to lay wool in two or more layers, this is done in a checkerboard pattern (so that the seams do not coincide). The video shows floor insulation in a house on a pile foundation.

For waterproofing, you can use glassine, polyethylene, isospan, and wind- and moisture-proof film. Polyethylene is the cheapest option, but it is not the best.

Important! In a wooden house on a pile foundation, it is imperative to treat all wooden floor elements with an antiseptic.

The insulation of a columnar foundation differs little from the insulation of a pile foundation; the same materials and techniques are used.

Conclusion

Insulating the foundation helps not only retain heat and reduce heating costs, but also protects the foundation, makes it more durable, performs a waterproofing function, and prevents dampness in the house. Wooden houses are usually made on a strip or pile foundation, which can be simply insulated with your own hands.

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The complex of protective measures to eliminate winter heaving of soils includes insulating the foundation of a wooden house. Depending on the operating conditions of the home, the heat insulation layer can be attached to the outside of the foundation strip (constant heating) or to the inside (during periodic heating of the building). The work can be easily done with your own hands, but there are several technologies that will be discussed further.

Overview of insulation options

Before sheathing the underground part of the foundation, the plinth from the inside or along the outer surface, you need to understand exactly why this is necessary. A layer of thermal insulation is necessary for the building to reduce heat loss; insulating the blind area solves another problem - preserving geothermal heat to eliminate swelling of clay soils.

There are several operating modes and building structures:

• a constantly heated house - the soil under the sole cannot freeze, however, it is necessary to insulate the blind area to prevent freezing of the soil layers adjacent to the reinforced concrete structures, which, when heaving, try to raise the foundation, or to create a crush-sliding layer of thermal insulation on the outer edge of the tape, which will prevent freezing tape, protects waterproofing, compensates for heaving forces;
• cottage with a basement floor - geothermal heat is stored in the lower level, it is only allowed to insulate the tape (basement) from the outside in order to shift the thermal circuit with the dew point to the street, forever eliminating condensation on the internal walls;
• lack of heating + strip foundation - to prevent freezing, the insulation must be glued to the tape outside, inside, placed under the sole (in the case of MZLF) and around the perimeter of the house under the floor or ceiling;
• periodic heating - the technology is completely similar to the previous case; on the outside, crushable sliding thermal insulation can be used.

Foundation insulation scheme

Attention: If the project includes a hanging grillage on pillars or piles, it is impossible to retain geothermal heat. It is useless to insulate the crawlspace, since there are no heat sources inside the underground. When using low grillages, the base and blind area are insulated from the outside.

Strip foundation

In 75% of cases, individual developers build strip foundations with their own hands. Depending on the depth of the sole, the effect of loads from swelling is not the same:

• the bottom of the deep tape is located below the freezing point of the soil, there is no heaving underneath it, however, the area of ​​the side faces on which the tangential forces of frost heaving act increases sharply;
• with MZLF the opposite is true - the lateral area of ​​the tape is too small for tangential forces to pull it to the surface, but uneven swelling is possible under the sole, since the freezing layer of soil is 0.7 - 1.5 m, a sand or crushed stone cushion cannot completely compensate for it able.

In both cases, it is enough to insulate the blind area and the outer edge of the tape, solving all the problems.

MZLF

In strip foundations, for ease of operation, a structural element is made - a plinth. It is often created from concrete, the service life of which is much higher than that of wall materials that work in contact with the ground. However, the reinforced concrete structure immediately becomes a giant bridge of cold:

• frost penetrates through the base to the ceilings and floors;
• heat loss increases;
• increasing energy consumption.

When insulating the basement from the outside, the following factors must be taken into account:

• the structure can protrude outward relative to the wall;
• go inside;
• or be flush with the facade cladding.

Insulation scheme for a shallow strip foundation.

In the first case, polystyrene foam insulation must be run over the plinth deep into the wall to prevent freezing of the concrete along the top edge. In the latest versions, the thermal insulation is combined with polystyrene foam for the external wall insulation, and there are no cold bridges.

Attention: The insulation layer of the underground and above-ground parts of the foundation must be continuous, although different problems are solved.

Deep laying tape

Even if the cottage does not have a basement, but the foundation strip is deep, it makes no sense to install polystyrene foam or stone wool from the inside. The soil under the house cannot freeze, unlike a reinforced concrete structure, in which moisture can accumulate. After several seasons, microcracks in concrete will open much larger, and the service life will decrease.

Attention: If all measures to eliminate swelling have been taken (warm blind area + drainage around the perimeter of the tape + non-metallic material under the base, in the backfill cavities), high-quality waterproofing of the concrete, then the deep tape in a house without a basement does not need to be insulated from the outside to its full depth.

Pile and column foundation

When constructing a grillage on piles or pillars with your own hands, you must consider the following points:

• hanging grillage - swelling is not dangerous for screw and bored piles in tubular formwork, pillars buried below soil freezing; it is useless to insulate the blind area and backfill, since there are simply no heat sources underground;
• low grillage - monolithic beams are protected from swelling by an air gap of 15 - 20 cm, covered on the sides with sheet materials, geothermal heat is retained by the base of the building, there is no particular point in a warm blind area, but the end of the grillage, which is a cold bridge, must be covered with a heat insulator from the outside.

Attention: There are design solutions for low grillages with floors on the ground in the form of a floating screed. Even when backfilling with non-metallic materials is used, freezing of the lower heaving layers under the grillage is possible. Therefore, polystyrene foam is placed under the screed from the inside, and the base is covered with insulation from the outside.

Is it possible to insulate from the inside?

The recommendations (albums of technical solutions) of leading manufacturers of extruded polystyrene foam contain options for buildings for seasonal residences, which are built with your own hands, mainly in gardens. If the building does not have heating, the base, together with the underground part of the MZLF, is covered with EPS from the inside. Vertical thermal insulation is connected to a horizontal layer of polystyrene foam under the floor along the ground.

Seasonal use (garden house)

The base is covered with a heat insulator from the inside in the only case - if there is no heating in the home at all. The thermal insulation diagram looks like this:

• expanded polystyrene is laid under the floors on the ground;
• fixed externally on the entire vertical surface of the MZLF;
• continues horizontally at the bottom of the trench along the perimeter of the dwelling (width 0.6 - 1.2 m).

Insulation of MZLF during seasonal operation.

An additional layer in the corners is not needed, nor is running along the top edge of the base. Cold bridges are inevitable here; the walls are usually not insulated.

Periodic operation (dacha)

When building a home in which heating is turned on periodically (for example, a summer house), a special insulation scheme is used:

• horizontal layer - under the floor along the ground in all rooms + under a blind area 60 - 120 cm wide from the walls of the building;
• vertical contour – base + underground part of the MZLF from the outside to the insulation of the blind area.

There is no need to glue polystyrene foam to the tape from the inside, since reinforced concrete freezes from the street. Unlike the warm blind area of ​​houses with constant heating, there is no need to increase the thickness of the EPS in the corners. Episodic heat losses in this case can be ignored.

Attention: Expanded polystyrene is not intended for outdoor use, as it is destroyed by solar ultraviolet radiation. After gluing, the base must be covered or covered with an opaque material.

Frequent mistakes when insulating the foundation.

Thus, all options have been considered when using insulation with your own hands from the outside and inside. This will help reduce the construction budget without reducing the efficiency of the building's thermal loop.

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The maximum heat loss in any building occurs through the ceiling and floor. It is for this reason that special attention should be paid to the issue of thermal insulation of the room. Before insulating the foundation of a wooden house, it is necessary to select the correct insulating materials.

Why is additional thermal insulation necessary?

Foundation insulation can be done from the outside and from the inside. In the first case, we can talk about preventing the penetration of cold air masses. In addition, insulating the base of a wooden building with your own hands eliminates the possibility of the foundation freezing. This increases the overall lifespan of the building. Among the advantages of this procedure, the following points should also be noted:

• increasing the service life of communication system elements;
• saving on home heating;
• protection from the influence of groundwater;
• preventing condensation formation;
• formation of a favorable microclimate indoors.

In order for the implemented thermal insulation layer to provide reliable protection, you must first correctly select the most suitable insulation materials.

Operational features of modern insulation materials

The modern market of insulation materials offers a wide selection of necessary products. However, despite the large assortment of goods, polystyrene foam, expanded clay, polystyrene and polyurethane foam are most often in demand among consumers. Often, foam glass is also used for external insulation.

Insulation	Operational Features
Polyurethane foam	Expensive material, the installation of which requires the use of special equipment. It is applied to the foundation surface by spraying. It has high thermal insulation capabilities.
Styrofoam	More affordable products in terms of price. The special structure of this material contributes to difficulties during installation - during cutting, the foam crumbles very much. Additional waterproofing may be required during work.
Expanded clay	The expanded clay layer is capable of absorbing moisture very well, due to which this material is positioned as a very good heat insulator. It creates a kind of cushion around the base of the house and prevents the penetration of cold air.
Foam glass	Used relatively recently. It is easy to process and prevents moisture penetration.
Polystyrene	Considering the flammability of such material, it is strongly recommended to refrain from using it as facade insulation. But for underground insulation, polystyrene is ideal. Its resistance to high moisture deserves special attention.

Earth as insulation

The easiest way to insulate the foundation part of a wooden house with your own hands is to fill it with earth. However, there are many questions about this method. This method is advisable to use only before the construction of walls begins.

The complexity of this insulation method lies in the need to use a large volume of soil. In a different scenario, achieving a positive final result will be very difficult. Moreover, even if you insulate the foundation from the outside with earth, you may not get the expected effect. This is due to the low thermal insulation potential of the material.

It should also be added here that insulating the foundation with earth with your own hands will involve great difficulties. In this case, there is a need to use specialized equipment, the rental of which is expensive.

Methods for insulating the foundation part of a wooden house

Insulating the foundation from the outside is most often done using expanded clay, polystyrene or polyurethane foam. The affordable price level of these materials and high thermal insulation capabilities have a direct impact on this choice. Moreover, the likelihood of resolving this issue with your own hands is attractive.

Insulation with expanded clay

The material absorbs moisture and removes it from the base of the house. In the case of a correctly implemented insulation scheme, an air gap is formed, which is also a good heat insulator. Thanks to this, the likelihood of foundation freezing is minimized. Do-it-yourself insulation of the base of a building with expanded clay involves several stages.

Stage No. 1

When insulating a built house, it is very important to thoroughly clean the surface of the soil. If necessary, cracks should be repaired. Waterproofing can also be carried out.

Stage No. 2

At the next stage, the trench is filled with soil. A small concrete blind area is made on top of the formed embankment. It will protect the thermal insulation material from moisture. The basement part of the base of a wooden house can be insulated by plastering.

Stage No. 3

If necessary, you can also insulate the basement with your own hands using expanded clay. The insulation is poured during the flooring stage. A sand cushion is first prepared, on top of which a layer of waterproofing is placed.

Polystyrene insulation

Polystyrene is presented in the form of a modification of polystyrene foam, characterized by mechanical strength. To achieve the maximum effect of insulation outside the house, it is recommended to give preference to material with fire retardant additives.

• Preparing the foundation. At this stage, the base of the house is freed from soil, dust, traces of oil and bitumen. If necessary, cracks are sealed.
• Installation of polystyrene plates. The insulation is attached to the base of the building using an adhesive mixture. It may take about 48 hours for the material to dry completely.
• Basement insulation. Polystyrene from a wall made of wooden material should be separated by using non-combustible insulation. Basalt wool can be used as such a material.

Insulation with polyurethane foam

The main feature of using such insulation is its connection to the depth of the material. The larger it is, the higher the quality of thermal insulation will be. To install polyurethane foam you will need to perform a number of steps:

1. Prepare the soil.
2. Prepare the foundation.
3. Waterproof the foundation of the house.
4. Installation of insulation.
5. Build external protection.

At the stage of excavation work, the base of a wooden house is completely freed from soil and excess dirt. For maximum effect, it is recommended to place a sand cushion at the bottom of the trench.

The cleaned foundation must be well primed. This will allow the thermal insulation material to perform its direct functions for the maximum period of time.

The implementation of a waterproofing layer allows you to minimize the likelihood of moisture penetration into the room. Thanks to this, the total service life of the building will tend to increase.

Polyurethane foam is positioned as a sprayed insulation. This structural feature of the material guarantees seamlessness and perfect evenness of the coating. High adhesion to any coating facilitates the issue of arranging external protection for the base.

Important! Polyurethane foam does not tolerate direct exposure to sunlight very well, therefore, if it is used to insulate the base, it is recommended to additionally cover the coating with other materials.

What's the result?

Insulating the foundation of a wooden house from the outside can be done using various thermal insulation materials, which are presented in a wide range on the market. High-quality preparation of the base is the key to a positive final result.

The use of insulation when arranging the foundation is a common way to improve the thermal insulation performance of a building and protect the foundation from the negative influence of sub-zero air temperatures. Among other insulation materials, extruded polystyrene foam has gained great popularity. Unlike conventional polystyrene foam, the material has an increased safety margin; in addition, the special shape of the boards allows the installation process to be significantly simplified.

Let's figure out how to insulate the foundation of a house with penoplex from the outside with your own hands. The procedure is very similar to thermal insulation of walls. Special heat-insulating slabs are fixed to the side parts of the foundation, which are located above and below the soil surface. The use of insulation allows you to reduce the rate of heat exchange between the foundation walls and soil layers.

Why insulate the foundation

Some owners of private houses refuse to insulate the basement, trying to save as much money as possible. At the same time, experts in the field of construction work insist that thermal insulation of this part of the house is simply necessary, and it is better to attach the insulation to the outside of the structure.

General scheme of foundation insulation with penoplex

The following arguments are put forward in favor of insulation:

• After insulation, the foundation becomes protected from the negative effects of sub-zero air temperatures. This factor is especially important in places with high humidity. If, when the temperature drops, moisture gets into concrete cracks, it begins to rapidly expand and ultimately tears and damages the concrete structure;
• The degree of protection of the foundation from temperature fluctuations increases. The concrete structure experiences much fewer cycles of compression and expansion, as a result, the service life of the building without major repairs to the foundation is significantly increased;
• The insulation becomes an additional barrier to groundwater that tends to penetrate to the foundation.

What is the best way to insulate the foundation: from the inside or the outside?

The foundation can be insulated from the inside or outside. Both methods have their advantages and disadvantages.

Internal thermal insulation

The advantages of internal insulation include:

• Improving the microclimate in the basement;
• Effective control of indoor dampness;
• Protecting the basement from groundwater penetration.

The disadvantages of internal insulation include:

• Such thermal insulation does not protect the foundation from soil freezing;
• Moisture easily enters the pores of the concrete base and destroys it;
• The dew point shifts inward.

Insulation from the outside

This insulation method has the following advantages:

• The foundation is reliably protected from freezing;
• The dew point shifts towards the street;
• The concrete base is protected from any negative influence from the environment;
• The overall service life of the premises increases significantly;
• Some insulation materials can provide additional strengthening of the foundation;
• When installing a thermal blind area, you can protect not only the foundation from freezing, but also the soil within a radius of about half a meter from the installed insulation.

External insulation will require more time and materials, and this is the only drawback of this method.

It is very important to understand that external insulation of the foundation provides a reliable guarantee of protection for the entire house, and thermal insulation from the inside will only protect the basement from the cold

Having assessed all the advantages and disadvantages of external and internal methods, we can conclude that it is better to give preference to external insulation.

In order for the insulation to fully cope with the tasks assigned to it, it is worth remembering that thermal insulation of the foundation should be carried out only after all the walls have been insulated. Be sure to treat all joints between the insulation with polyurethane foam - this will increase the efficiency of the thermal insulation of the room.

By the way, preference is given to insulating the foundation from the inside only if for some reason it is impossible to install insulation from the outside.

What is the best way to insulate?

When planning work on installing thermal insulation for the foundation, the issue of choosing and purchasing suitable insulation is initially resolved. The material for foundation insulation should have the following characteristics:

• Be resistant to deformation against the background of constant pressure from the soil;
• Do not absorb moisture from the soil.

On the modern market, insulation materials are presented in a wide range, and a newcomer to the construction industry may get confused in the abundance of offers. It is worth saying that the common insulation “mineral wool” is not suitable for thermal insulation of the foundation. Not only is it not durable, but it also absorbs moisture well, as a result of which all its positive performance characteristics are negated.

Despite fire resistance and low thermal conductivity, mineral wool has a significant drawback - high hygroscopicity

In modern construction of private houses, two materials are best suited for foundation insulation:

• Polyurethane foam.

Polyurethane foam is a modern insulating material that guarantees thermal, sound and water protection of a concrete structure. The material is sprayed onto the surface using special equipment in several layers. This application technology eliminates the appearance of gaps and seams. The advantages of the material include:

• Possibility to apply thermal insulation coating without seams or gaps;
• Excellent adhesion characteristics;
• Low thermal permeability;
• Steam protection;
• Increased reliability;
• Long service life;
• There is no need to purchase additional material for steam and water protection of the foundation.

The main and rather significant drawback is that special equipment is required to lay the material, as a result of which the process becomes impossible to implement at home. In addition, polyurethane foam has a high cost.

Penoplex, in turn, does not require special skills or special equipment for installation. Among other things, it has the following advantages:

• The cellular structure does not allow moisture to pass inside, as a result of which the slabs do not collapse over time after freezing;
• Increased strength characteristics;
• Ensuring a long service life of the foundation;
• Low cost;
• Long service life of the material;
• Preservation of thermal insulation characteristics throughout the entire service life;
• Rodents do not use the material as food, unlike regular foam.

Penoplex insulation reduces heat loss by 20% and helps the foundation last longer

Penoplex is an improved version of polystyrene foam. The material allows moisture to pass through very easily, and after several cycles of defrosting and freezing it will simply crumble into segments. Let us add that several years ago, expanded clay was also in demand on the construction market as insulation for the foundation. The material is inferior to penoplex due to its high cost, as well as reduced efficiency in providing thermal insulation.

Calculation of insulation thickness

In addition to the correct choice of insulation, it is necessary to pay attention to calculating its optimal thickness. If the penoplex is of insufficient thickness, this may result in freezing of the foundation and transfer of the dew point into the basement, which will ultimately lead to the appearance of condensation on the walls and an increase in humidity levels.

You should not take too thick a material: this will not increase the degree of thermal insulation, but the costs will significantly hit the family budget.

Correct calculation of the thickness of the insulation material is the key to warmth in the house, absence of humidity and minimal financial costs.

Thermal resistance is denoted by the Latin letter R. This value is constant, but for each region the value is different and depends on general climatic conditions. For example, for the Moscow region it is equal to 3.28 m 2 K/W. For other regions of Russia, the value can be taken from the table:

Region	Thermal resistance, m 2 K/W
Moscow	3,28
Krasnodar	2,44
Sochi	1,79
Rostov-on-Don	2,75
Saint Petersburg	3,23
Krasnoyarsk	4,84
Voronezh	3,12
Irkutsk	4,05
Yakutsk	5,28
Volgograd	2,91
Astrakhan	2,76
Ekaterinburg	3,65
Nizhny Novgorod	3,36
Vladivostok	3,25
Magadan	4,33
Chelyabinsk	3,64
Tver	3,31
Novosibirsk	3,93
Samara	3,33
Permian	3,64
Ufa	3,48
Kazan	3,45
Omsk	3,82

Thermal resistance is calculated using the formula:

R = h 1 /λ 1 +h 2 /λ 2

where h 1 is the thickness of the foundation (in meters), λ 1 is the thermal conductivity coefficient of the foundation (for a reinforced concrete foundation λ 1 = 1.69 W/m ° K); h 2 – thickness of the insulation material (in meters); λ 2 – thermal conductivity coefficient of insulation (for penoplex λ 2 =0.032 W/m ° K).

Thermal conductivity coefficient of various materials

Therefore, the thickness of the insulation is calculated using the formula:

h 2 = λ 2 (R-h 1 /λ 1)

Let's consider an example of calculating the thickness of thermal insulation material for a private house in St. Petersburg with a reinforced concrete foundation half a meter thick (h 1 = 0.5 m):

h 2 = 0.032(3.23-0.5/1.69) = 0.094 m, that is, 94 mm.

The value must be rounded up to the nearest centimeter. Thus, the thickness of penoplex for insulating a half-meter reinforced concrete foundation of a house in the Leningrad region is 10 cm.

Insulation technology

Following the sequence of penoplex insulation will allow even novice builders to cope with the process.

It is advisable to carry out work on insulating the foundation at the stage of construction of the future house. This makes the process much easier. But what to do if the house was built several years ago and was not initially insulated?

In this state of affairs, the foundation is excavated to the ground. Ideally, dig to the depth of the soil, but if working resources are limited and it is not possible to cope with such a volume of work, it is worth digging a trench near the foundation for the length of the insulation used.

The thickness of the trench is determined by adding the thickness of the insulation sheet used, as well as the minimum space required to complete the work. Making a trench too wide will be inconvenient, especially if you do not plan to involve specialized construction equipment in the process. A trench that is too small will complicate the work process.

If you decide to use special equipment for excavation, it is recommended to be careful not to damage the foundation walls

The bottom of the dug trench must be filled with sand, the layer of which should not be less than 20 centimeters. Be sure to compact the sand thoroughly and make a slight slope in the direction opposite to the foundation. Sand will act as additional protection against moisture.

After the foundation has completely dried, it is necessary to begin preparing the future surface for laying sheets. We carefully clean the foundation wall and plinth from adhering soil, damaged pieces of concrete and other contaminants. It is most convenient to clean with a brush with stiff synthetic bristles.

After cleaning, it is necessary to level the surface: only a flat concrete wall will ensure a reliable fit of the waterproofing coating.

Leveling the foundation walls is carried out according to the following principle:

• We install beacons on the surface of concrete walls, the distance between which should be at least 1 meter from each other. Beacons must be mounted on the entire surface where insulation will be installed in the future;
• Prepare the solution. To do this, thoroughly mix 4 parts sand and 1 part cement in a container, after which we begin adding water. Make sure that the consistency is not too liquid or dry, otherwise the leveled surface will not be reliable;
• Pour the mixture onto the surface from bottom to top;
• We apply a rule to the beacons and with a sharp movement from top to bottom we level the surface, while removing excess solution;
• After the first layer of the mixture has dried a little, you can apply the finishing layer, which will finally level the surface.

To level the walls, it is recommended to use a rule about two meters long, since working with a float takes too much time

This method is suitable for more or less even walls. If differences of more than 2.5 centimeters are observed on the surface, a reinforced mesh is additionally used.

You should proceed to the next stage of work only after the cement mixture has completely dried. On average, the process takes from 7 to 20 days. If a recently poured foundation is being insulated, insulation begins no earlier than a month after installation.

It is better to isolate the foundation from moisture penetration in two layers with the application of bitumen mastic and waterproofing Technonikol.

It is recommended to buy ready-made bitumen mastic - it’s easier than preparing the solution yourself. If you decide to do it manually, then be sure to add used machine oil to the mixture, which will protect the mastic from cracking when the air temperature drops.

It is most convenient to apply mastic using a roller. The layer thickness must be at least 2 mm. After the bitumen has dried, we proceed to installing Technonikol. The sheets are glued from top to bottom. The back side is melted using a burner, and the joints between the sheets are covered with mastic. The material fills all small pores and cracks and prevents moisture from causing Technonikol sheets to peel off.

To avoid cracking of the mastic under the influence of temperatures, it is recommended to add used machine oil to the solution at the rate of 5 liters of oil per 12 - 15 kg of bitumen

Installation of penoplex

It is most convenient to install penoplex sheets using an adhesive solution or foam glue. Additionally, you can use dowels in the form of umbrellas, but they violate the integrity of the insulation sheet.

Apply glue to the sheet using a notched trowel, then the insulation will lie smoothly, without gaps between the sheet and the foundation wall.

Experts advise giving preference to foam glue in cylinders. It not only simplifies and speeds up the process, but is also used more economically.

After pressing against the wall, the adhesive should cover at least 40% of the foam board

If the sheets are laid in two levels, then a checkerboard order must be observed. In this case, the distance and gaps between the insulation sheets should be minimal. The gaps can be additionally treated with foam.

Reinforced mesh and finishing

To enhance the overall strength of the structure and protect the insulation from external sources, it is recommended to use reinforced mesh. The material is used only if the foundation is above the ground and can be damaged in the future.

The mesh is laid on foam sheets, and an adhesive solution is placed on top for fixation.

At the next stage, they begin finishing the foundation. You can get by with regular plaster, use siding or any other material for exterior finishing.

If desired, the resulting trench can be filled with sand or expanded clay, and the materials will act as an additional layer of insulation.

Backfilling of the trench is not carried out completely, but space is left for the formation of a warm blind area. The work is carried out in several stages:

1. At a depth of about 30 cm from the surface of the earth, pour a layer of sand 10 cm thick and compact it thoroughly;
2. We spread waterproofing material at the foundation (ordinary roofing material will do, the joints between which are lubricated with bitumen mastic). The boundaries should be adjacent to the foundation on one side and extend from it to a width of about a meter;
3. We lay foam sheets on the waterproofing layer, and treat all joints with glue or foam;
4. Next, a blind area made of concrete mixture is constructed. It must be done at an angle from the foundation, which allows for further drainage of wastewater.

The foundation is the foundation of your home, so don’t skimp and do the insulation well

Only maximum compliance with all the rules for laying insulation on the foundation will protect the foundation of the house from freezing and subsequent premature destruction. Savings on foundation insulation may result in more serious financial costs in the future.

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Thermal insulation of the foundation is no less important than the thermal insulation of the walls, especially in areas with a harsh climate. Frozen soil cannot protect the foundation of a house from moisture and cold, and the foundation itself, after repeated freezing, begins to collapse faster. To get rid of these problems and reduce the cost of heating your home, you need to know how to insulate the foundation of a house from the outside, and how you can do it yourself.

The foundation of a house is regularly exposed to moisture, increased load, and temperature changes. After the onset of frost, the accumulated moisture freezes, destroying the material, and through cracks in the concrete the cold penetrates into the home. As a result, the house always has cold floors, dampness emanates from under the baseboards, and condensation or frost appears on the basement walls (in severe frosts). For thermal insulation to be effective, the insulation must have the following characteristics:

• low thermal conductivity;
• waterproof;
• good mechanical strength;
• resistance to temperature changes.

There are no strict requirements for the vapor permeability of the material, but insulation materials with low vapor permeability are usually used, just like the concrete foundation itself. The flammability of the material is not of great importance, because the underground part of the building is least susceptible to fire risks.

Which insulation to choose

Mineral wool insulation for foundations is not the most suitable option: they tend to accumulate moisture, losing their thermal insulation properties, and are not sufficiently resistant to mechanical loads. Soil pressure will lead to shrinkage of the material, and the effectiveness of insulation will decrease to zero.

Prices for mineral wool

But polymer insulation does not have such disadvantages and fully meets the necessary requirements.

Let's take a closer look at their characteristics.

Expanded polystyrene

Expanded polystyrene, or polystyrene foam, is very widely used in thermal insulation. It is lightweight, its sheets have the correct shape, and therefore installation is not a problem even for a novice master. The material is available in various densities and thicknesses, and depending on this has certain areas of application. Only the densest sheets with a thickness of at least 50 mm are suitable for foundations; the rest are best used for insulating walls and partitions.

In terms of thermal conductivity, foam plastic is much more effective than wood, expanded clay, and mineral wool insulation. It almost does not absorb water, is not prone to shrinkage and deformation, and serves as an excellent sound insulator. In addition, polystyrene foam boards fully retain their properties when exposed to salt and chlorinated water, soap solutions, and weak acids. The insulation can come into contact with bitumen mastics, lime, water-soluble adhesive solutions and cement plaster.

For slab foundations, as well as deeply buried foundations, it is necessary to use polystyrene foam marked PSB-S-50, which is able to withstand heavy mechanical loads and provide reliable protection against soil swelling. For columnar and standard strip foundations, PSB-S-35 grade foam is used.

All other varieties are not suitable for foundations due to the low density and fragility of the sheets.

Expanded polystyrene made by extrusion is significantly superior to polystyrene foam in all respects. It is many times stronger, absolutely moisture-proof, and has the lowest vapor permeability and thermal conductivity. Microorganisms also do not develop in it, even under conditions of prolonged exposure to dampness.

Foundation insulation with extruded polystyrene foam - EPS

EPS boards with a smaller thickness have a much greater effect. To thermally insulate the foundation in a temperate climate, an insulation thickness of 40 mm is sufficient, in northern conditions - about 60 mm (a two-layer laying of slabs with a thickness of 30 mm is recommended). For ease of installation and greater packing density, the slabs are equipped with tongue-and-groove joints.

They are attached to the base using an adhesive solution and disc-shaped dowels.

Laying of EPS slabs can be done vertically (when insulating columnar and strip foundations) and horizontally (when installing a slab foundation).

Due to its increased strength, the material perfectly tolerates the load from the concrete layer, does not flatten or shrink, unlike polystyrene foam and polyurethane foam. The most popular brands of extruded polystyrene foam are Penoplex and TechnoNIKOL.

Main characteristics

Sprayed thermal insulation, or PPU, is increasingly used to insulate foundations. Polyurethane foam forms a very durable seamless coating that is resistant to adverse influences. At the same time, it simultaneously performs the functions of vapor and waterproofing, which greatly simplifies the work process. Another useful property of this insulation is its high adhesion to the base. It adheres equally firmly to stone, concrete, brickwork, and wooden structures, is easily applied to hard-to-reach areas, and fills the slightest cracks.

Polyurethane foam is applied in two ways - pouring and spraying. The first option is more labor-intensive and expensive, so it is rarely used when insulating private houses. The second method is actively used to insulate the entire building - from the roof to the foundation. Before application, the components are mixed in a foam generating unit with air and the finished mass is sprayed under pressure onto the working surface. Within a few seconds, the composition hardens, and upon completion of the work, you can immediately begin finishing. The only disadvantage of such insulation is that it is impossible to do without installation, and this is an additional cost.

In addition to the described insulation materials, bulk materials, in particular expanded clay, can be used for foundations. It is environmentally friendly, inexpensive, has good thermal insulation characteristics, and is suitable for both vertical and horizontal insulation. But since expanded clay can absorb moisture, losing some of its properties, and the work process requires more effort and time, this insulation is used less and less, giving way to more modern and effective materials.

Prices for expanded polystyrene

Expanded polystyrene

Foundation thermal insulation technology

Insulation of pile, column and strip foundations can be carried out both during the construction process and during the operation of the house. Before installing the insulation, the base must be prepared, which includes cleaning, sealing cracks, and installing waterproofing. The better the preparation, the more effective and durable the result. Slab foundations are insulated directly during construction, because thermal insulation slabs are located horizontally under a layer of reinforced concrete.

Strip foundation

The most labor-intensive stage in insulating such a foundation is excavation work. The foundation must be excavated to its base or to the level of soil freezing. If possible, it is better to hire special equipment, because digging by hand will take a lot of time and require a lot of physical effort. The foundation is dug around the entire perimeter to a width of at least 1 m, then the bottom of the trench is compacted and covered with a layer of sand and crushed stone.

The foundation walls are cleaned of soil with a stiff brush and left open for 10 days to allow the moisture to evaporate. For this reason, work must be carried out in the warm and dry season.

Step 1. The dried walls are carefully inspected for damage, and any identified defects are eliminated. Before sealing, cracks are opened and cleaned of dust; if necessary, the surface is leveled with cement-sand plaster. If unevenness exceeds 20 mm, the plaster is additionally reinforced with metal mesh. After plastering, you must wait until the surface is completely dry.

Step 2. Waterproof the foundation. It is most convenient to use coating waterproofing, for example, polymer, rubber or bitumen water-soluble mastics. Compositions containing organic solvents cannot be used, since polystyrene foam boards are destroyed upon contact with them.

To improve adhesion, the surface is pre-treated with a bitumen primer, applying it in a thin continuous layer. It takes about a day for the primer to dry, after which you can begin applying mastic.

Step 3. Stir the mastic; if the mass is too thick, add a little water.

Prices for bitumen mastic

For application use a wide brush with dense bristles or a roller. The composition is evenly distributed over the walls in a continuous layer, very carefully coating the corners. The layer should not be transparent, but it should not be made too thick, so that streaks do not form. The mixture is rubbed well over the surface, filling the smallest pores of the depression. When the first layer has hardened, apply the second in the same way. Usually two layers are enough, but if the area is often flooded with groundwater, it is recommended to apply 3 layers of mastic.

Step 4. After the waterproofing has dried (after 5-7 days), you can begin installing foam plastic or EPS. To attach the plates, a special adhesive composition is used, for example, ALLFIX, Ceresit CT 83, Titan.

Installation of insulation is carried out from the bottom up, in horizontal rows, with mandatory bandaging of the vertical seams. Apply glue, press the slab to the surface and check its position with a level. When installing the next slab, it is necessary to align the mounting grooves as tightly as possible so that the joints are barely noticeable.

Advice. When laying thermal insulation slabs in two layers, the joints of the lower layer must be completely covered by the slabs of the upper layer. Combining joints will lead to the formation of cold bridges, which means that the effect of insulation will be lower than planned.

Step 5. As a rule, the underground part of the insulation does not need additional fixation, because after backfilling the material is tightly pressed with soil. But in the above-ground part of the slab it is recommended to strengthen it with dowel nails with wide heads. Fastening is carried out after the adhesive solution has completely dried. To do this, through holes are drilled in the slabs (in the center of the slab and in the corners) and buried 40-50 mm into the base. Next, insert the dowels and hammer them in until they stop.

Step 6. To protect the surface of the slabs from accidental damage, plastering is performed with a fiberglass reinforcing mesh. Apply the adhesive solution to the insulation, spread it in an even layer 40-50 mm thick, lay a mesh on top and forcefully smooth it with a spatula, deepening it into the solution. For convenience, it is recommended to cut the mesh into pieces and overlap them by 10 cm.

Step 7 After a day, a final leveling is carried out, and when this layer dries, the surface is treated with a grater and emery cloth.

Step 8 Fill the trench with soil, leaving a distance of about 30 cm to the top. The soil is compacted well to reduce shrinkage. A layer of sand 10-15 cm thick is poured on top, which is also carefully compacted, and then a waterproofing membrane and a layer of insulation are laid at a slight slope from the wall. The final stage is the arrangement of the blind area by pouring a concrete screed.

If it is decided to insulate the foundation with polyurethane foam, there is no need for leveling and waterproofing. After digging a trench and clearing the base of the earth, it is only necessary to eliminate cracks and also remove peelings, if any. When the foundation walls are dry from moisture, you can begin applying polyurethane foam. You can rent a spraying installation from a construction company or buy it, but if you do not have the skills to work with such equipment, it is better to turn to specialists. After the material has hardened, the trench is filled with soil, and a blind area is made on top, as described above.

Columnar foundation

Thermal insulation of columnar and pile foundations is performed a little differently. To thermally insulate the space between the grillage and the ground, it is necessary to build a fence that acts as a plinth. This design does not carry a load, so there are no special requirements for the mechanical strength of materials.

Step 1. A narrow trench up to half a meter deep is dug between the foundation pillars, and a third of it is covered with a layer of sand and small crushed stone.

Step 2. A frame of metal rods is laid on top and a layer of concrete mortar is poured.

Step 3. After the concrete has hardened, the space is bricked around the entire perimeter, leaving small vents in the opposite walls for ventilation.

Step 4. When the masonry is dry, insulation boards are glued to the outside and then plastered using reinforcing mesh. After the plaster has dried, the trench is filled with soil and compacted.

Finally, decorative finishing of the base is carried out - this can be painting, applying decorative plaster, or facing with artificial stone.

Instead of a brick fence, you can install a frame made of timber or a metal profile between the foundation supports. Before installation, the timber must be treated with antiseptic impregnation and dried well. The beams are fastened using metal corners, bolts 65-80 mm long and self-tapping screws; it is preferable to use welding to assemble the metal frame. After installation, the frame is sheathed with EPS or foam plastic boards, and corrugated sheets or plinth panels are attached on top.

Slab foundation

With horizontal insulation, the slabs can also be laid in one or two layers. Most often, insulation with a thickness of 50 or 100 mm is chosen for slab foundations. Thermal insulation begins after the foundation pit has been prepared and the sand cushion has been backfilled.

Step 1. The sand layer is thoroughly compacted over the entire area and leveled horizontally. The smoother the base, the denser the insulation will lie.

Step 2. Film and heat-insulating boards are laid on the sand cushion, joining the mounting grooves. In each subsequent row, the joints are shifted by the width of half the sheet.

Advice. When laying insulation in two layers, the lower slabs are placed in rows along the long side of the foundation, and the upper slabs are placed in rows along the short side. This will not only eliminate cold bridges, but will also further strengthen the strength of the thermal insulation layer.

Step 3. Along the perimeter of the foundation, close to the slabs, formwork is installed, inside which a reinforcing frame made of steel rods is mounted. Concrete is mixed and poured.

Step 4. After the concrete has hardened, a blind area is made. Carefully level and compact the sand with a slight slope from the foundation. The slabs are laid tightly and covered with a waterproofing membrane on top. The membrane sheets are overlapped by 10-15 cm. Next, they are backfilled with sand, again everything is leveled and compacted.

Prices for thermal insulation materials

Thermal insulation materials

Video - How to insulate the foundation of a house from the outside

Video - Insulating the foundation with polyurethane foam

Video - Insulating a slab foundation