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.

Why do you need to insulate the foundation from the outside?

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

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.

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.

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.

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.

Recently, among the residents of our country, the fashion for building wooden cottages has been gaining increasing momentum. After all, people sometimes want to escape from the bustle of the city and be alone with nature. Wood materials are ideal for the construction of such houses. Where does the construction of any building begin, no matter what material is used during its construction? Of course, with the construction of the foundation. The main topic of this article is the insulation of the foundation of a wooden house.

It is much easier to build a foundation for a house made of wood, because in this case quite acceptable loads will be placed on the supporting structure.

There are a number of requirements for foundation walls that relate to strength. To meet them, materials are used that can withstand high loads. Indeed, during the operation of the structure, pressure from structures located above will constantly be exerted on the foundation. For example, floors between floors.

To better understand, imagine a fragile little table. If you put a lot of weight on it, the tabletop will begin to sag and eventually break. With the foundation everything is about the same. The base, which is a kind of substrate, is subject to pressure from the structure installed on top. The loads are quite significant. This is where the requirements for strength come from.

Why is the load-bearing structure insulated?

Insulated foundation in section.

Heat loss is an inevitable drawback that manifests itself after the construction of absolutely any foundation. Sometimes during the construction of wooden houses they do without erecting a supporting structure. This is due to the lightness of wood compared to stone. However, many wooden houses still have an appropriate foundation. One cannot discount such a procedure as thermal insulation of the foundation, even if wood conducts heat much better than stone.

In cold weather, heat loss will be unreasonably high. And it turns out that due to the properties of wood and special insulation materials, the house will be warm, and the lower part will be cold. In this case, you will have to spend a lot on utilities so that the house is always warm.

How to insulate the foundation of a house?

According to most experts, polyurethane foam is the best material for insulating the foundations of wooden houses. This material has very low thermal conductivity, which means that less of it will be required for thermal insulation in a wooden house than other thermal insulators. The size of the thermal insulation layer depends on the thickness of the base and the heat-insulating material. Usually it is 30, 50 or 100 millimeters.

Of course, polyurethane foam alone is not enough. Insulation with foam plastic and expanded clay is also carried out. However, polyurethane foam copes with the tasks somewhat more effectively. He has proven himself to be the best during the construction of many objects. In general, factors associated with the project directly influence the choice of waterproofing material. Know that polyurethane foam is durable and reliable. But you shouldn’t give up other materials. Project requirements should be taken into account. Perhaps polystyrene foam is the best option for realizing your ideas.

In addition, you can use foam glass, which is also a good heat insulator. It is made from foamed glass. Silicate glass is heated at a temperature of 1000 degrees, then, as it cools, it acquires excellent mechanical and thermal insulation properties.

Thermal insulation of the supporting structure of a wooden house with polyurethane foam

There are only two ways - thermal insulation from the inside or outside. The first option means carrying out work in the basement from inside the house, the second - on the street. If you have chosen polyurethane foam, then insulation comes down to simply spraying this material onto the base. Spray guns are great for this type of work. 35 kg/m3 – this should be the density indicator of the material.

You can watch a video that shows how to insulate, as well as the advantages of insulation by spraying polyurethane foam.

It is best to insulate the foundation from the outside. This will save the base from freezing, which has a positive effect on the entire structure. If the house has a basement, the microclimate in it will improve.

Polyurethane foam should be protected from sunlight if it is decided to use it outside the building. Plastering based on a metal or polymer mesh is quite suitable. However, there is another option - fixing porcelain stoneware or stone using special glue.

Internal and external thermal insulation are almost the same technologies. If you decide to insulate the house from the inside, then you need to cover all the walls, from floor to ceiling, with polyurethane foam.

Often, when insulating the foundation of a wooden house, not only the walls, but also the ceiling and floor are insulated - this also has a beneficial effect on the microclimate. The surface on which polyurethane foam is sprayed is finished with standard cladding. You can choose any material you like.

Other materials used in thermal insulation

The installation of other heat-insulating elements directly depends on the type of material itself. For example, foam boards are attached to the surface with glue. Expanded clay is poured, then a layer of waterproofing is created. As a rule, such work is not particularly difficult, but in terms of the simplicity of working with polyurethane foam, it is incomparable.

To insulate a building using polyurethane foam, you just need to use a spray gun. When insulating with foam plastic, you need to do much more physical movements: treat the slabs with glue, attach them to the surface, make sure that the layer is even, etc. Doing it correctly, and even with your own hands, is not so easy.

How to insulate a house on a columnar foundation

Another option for insulation is in the section.

Thermal insulation of a columnar foundation is a process that constantly raises many questions. The intake device is the most acceptable option when insulating a columnar foundation.

A fence is a kind of partition that fills the space between the foundation piles. It can be made from various building materials. Let's look at them.

• Wooden pick-up. In this case, the fence can be made of timber, boards or logs. A trench 30-40 centimeters deep is dug between the pillars. Then a cushion of sand and gravel is placed there, and bars with grooves are attached to the pillars, into which 4-6 centimeter boards are inserted to form wooden panels. After this, the lower part of the intake is covered with expanded clay.
• Brick fence. In this case, a trench is also dug and a cushion is filled. The bricks are placed in a row, one or two at a time.
• Insulation sheets. This method is used when insulating a private house, the length of the foundation pillars of which reaches 0.8 meters. Steel sheathing is attached to the posts. Insulation (foam plastic, expanded polystyrene) is attached to it from the inside. On the outside there are corrugated sheets. The space between the insulation and the ground is filled with expanded clay.

For aesthetic beauty, you can make blind areas, which are a waterproof covering (asphalt or concrete strip) that runs along the entire perimeter of the building from the outside. The blind area will protect the building from floods and precipitation.

Tips and rules for thermal insulation of old foundations

Insulating an old foundation is perhaps the most complex process of all possible thermal insulation processes. During the winter, you may feel a cold floor or notice heat on the outside of your home, which indicates heat is escaping. In this case, you need to wait until spring or summer and provide high-quality insulation between the lower crown and the foundation so that the heat is retained in the house and does not escape through cracks. Almost every well-worn foundation of a village house has such “symptoms”.

You can do the following when carrying out thermal insulation in an old wooden house:

1. dig a recess 1-1.4 meters wide and 50 centimeters deep around the walls of the house; if there is swelling of the soil, then it should be taken into account when digging;
2. pour 20 centimeters of sand into the bottom of the mini-trench and compact it thoroughly;Guys! Potency returned at 60 years old! For pennies I regained my iron POTENTITY! Write down the recipe: take one...

A wooden house has always been considered warmer. This is understandable, since wood has very low thermal conductivity and “saves” the thermal energy of the room by itself. But the weak point of a wooden house is its foundation. Therefore, even experienced builders often ask how to insulate the foundation of a wooden house.

It has been theoretically proven that the lion's share of heat loss in a wooden house occurs due to the fact that the thermal insulation of the foundation almost always leaves much to be desired.

A modern wooden house does not have such disadvantages, since people have already learned how to insulate the foundation during construction. This begs the desire to insulate the foundation, doing this with minimal losses to the nervous system and maximum efficiency.

The most reliable way is to insulate the foundation from the outside and inside. But for this you will have to raise the floor, install insulation, lay the floor and finish work after the repairs have been made. This path is too long and expensive. You can simply insulate the foundation of a wooden house from the outside, and the efficiency will be about 75% of the double-sided insulation proposed above.

The most “ancient” way to insulate a foundation is simple to the point of primitiveness - this is the usual addition of sand around the base of the building.

The bedding layer can resist freezing of the foundation for a long time. But this method is not suitable for modern architecture, since it all looks very unaesthetic. Currently, foundation insulation is carried out using more advanced methods. Since they are very different in their technology, we will describe them separately.

Frost protection, its types

This is not the name of the method, but just the main task of insulation. To install such protection you will need:

• shovel;
• boards or other material for formwork;
• roofing felt;
• insulation directly (it is better to take expanded clay, but other material may be suitable);
• cement and sand.

A layer of soil is removed along the perimeter of the wooden house in the immediate vicinity of the base. Your instinct should tell you the depth, but you shouldn’t overdo it in this direction: with a large trench depth, you can ensure that the foundation under the influence of the gravity of the entire house can give additional shrinkage.

The walls, of course, will not crack (this is also an advantage of wooden houses), but the foundation may lose its integrity. Then it will have to be insulated more radically. It is enough to limit yourself to a depth of about 45 cm. In order to adequately insulate the foundation, depth does not have to be considered the basis of all work. A wooden house needs a solid foundation, so it is better not to dig deeper.

So, the trench is ready, and you have to make the formwork. The design can be anything, since it is not of fundamental importance. The bottom and walls of the resulting structure will have to be laid with roofing felt. This measure is necessary to ensure that the insulation does not fill with moisture, otherwise it will not “work”.

Next, insulation comes into play: we pour expanded clay into the resulting foundation pit, cover it all with another layer of roofing felt and fill it up. The work is not finished yet, as there is a blind area to be made. Do not forget that the width of the blind area should cover the laid thermal insulation.

It makes sense to take care of forming a certain slope around the foundation of a wooden house from the outside. This is necessary to ensure that rain or melt water does not stagnate and penetrate into the insulation. This will be a kind of guarantee that the insulation will not have to be replaced soon.

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Application of polyurethane foam or polystyrene foam

Now let’s look at the question of how to reliably insulate the foundation of a wooden house using more modern materials. To solve this issue you will need the following materials and tools:

• hammer;
• heat insulator (polyurethane foam or polystyrene foam sheets are quite suitable);
• reinforcing mesh;
• plaster (it is better to take decorative plaster for exterior work);
• screwdriver and set of screws;
• roofing felt or bitumen.

Insulating the foundation of a wooden house using these materials is easier than you might think. First, the base is cleared of earth and plaster. After it has dried, you can begin the main work. It is better to immediately waterproof it using roofing felt or ordinary bitumen.

If you use bitumen, then at the same time you should also insulate the foundation. In this situation, bitumen will also work like glue. But you need to monitor the temperature of this “glue” so as not to spoil the structure of the insulation. We glue the thermal insulation onto a cooled but still viscous layer of bitumen. We don’t really count on the reliability of gluing and fix the thermal insulation.

You can use long screws or dowels, the main thing is to securely fasten the insulation to the foundation. And one more point: we do not allow gaps between the insulation sheets. Any “loophole” for moisture and cold is quite capable of leading to a wooden house being attacked by fungus. The foundation of a wooden house needs very reliable insulation from moisture.

Today, one of the most effective options for thermal insulation of wooden houses is considered to be insulation of their foundation. If done correctly, you can save up to 25% of the heat leaving the house. In modern construction, several options for such insulation are used. The choice depends on the type of supporting foundation and the financial capabilities of the home owner.

Why do you need base thermal insulation?

Insulation of the foundation of a wooden house can be internal and external. In any case, thermal insulation will help prevent many of the destructive factors.

External insulation (regardless of material) protects against freezing and cold air entering living rooms, allowing you to save approximately 1/3 of electricity. In addition, the foundation, insulated from the outside, is protected from the destructive effects of moisture from the soil, which extends the life of communications and the very foundation of the building.

Arranging thermal protection from the inside contributes to the formation of an optimal microclimate in the basement and, accordingly, in the house, creates an obstacle to the penetration of groundwater and the accumulation of condensation, which eliminates the appearance of mold.

Types of foundations and methods of their thermal insulation

Depending on the method of support on the ground, the following types of foundations used for wooden buildings can be distinguished:

• columnar;
• monolithic;
• tape;
• pile

For the construction of wooden and frame houses, in most cases, shallow foundations are used. They are made of concrete or brick in the form of a strip or slab structure. It is better to insulate such a foundation from the outside. The thermal insulation layer is located at a distance of approximately 1.5 m, behind which a frost-free layer of soil is created.

Columnar base

This type of foundation is constructed from pillars that are dug below the frost line by about 2 m.

The posts are located at all corners and intersection points of the building structure, as well as in places with maximum load.

In this case, the base is made thick and the floors are thoroughly insulated; there is no basement.

Pile structures

When making a screw base, instead of monolithic pillars, piles are used that are screwed into the ground.

It is insulated in the same way as a columnar foundation.

Monolithic is made in the form of a slab under the base of the house; in this case, a basement is not provided.

To equip its buried version, they dig a pit; for a shallow one, the top layer of soil is simply removed. Such a foundation can be insulated with any modern materials only from the outside.

Tape

A strip foundation is created under the walls along the perimeter of the building, provides for a basement, it can be made of concrete blocks.

It can be insulated from the outside and inside without any problems.

Choice of insulation

The most popular insulation materials for insulating the base from the outside are:

• expanded clay;
• polystyrene foam, polystyrene, penoplex;
• polyurethane foam.

cotton wool

Internal insulation of the foundation of a house is usually carried out using cotton wool materials (mineral, glass, basalt).

They will require double-sided waterproofing (to avoid getting wet, lumps, and cold penetration through the voids).

Styrofoam

You can also use polystyrene foam. It is accessible, cheap, and easy to install. But this is a fragile material, so you need to work with it carefully.

Despite its fire safety, when insulating the outside, experts give preference to foam plastic, since contact with electrical wiring is excluded, and the operational characteristics of the insulation make it possible to create an effective thermal insulation system.

PPU

Polyurethane foam is considered a universal insulation material. It is commonly used as a thermal insulator under floors and in basements.

Apply by spraying onto surfaces. A heat-insulating layer forms after drying.

It does not require additional insulation, is very light, and lasts a long time.

To insulate the foundation, penofol is also used - foamed polyethylene covered with aluminum foil. It is thin, retains heat well, and protects against moisture.

Used as an additional material with other types of insulation.

EPPS

Most often, extruded polystyrene foam is used for any method of insulating a load-bearing base.

This is a universal material that has excellent moisture-repellent properties, is relatively cheap, and has a long service life.

Expanded clay

Expanded clay is a good choice for insulating a shallow foundation. Due to the porous structure of the granules, it retains heat well. It is an environmentally friendly and inexpensive material. Thermal insulation with expanded clay is often carried out externally.

To do this, the foundation is dug out around the entire perimeter and cleared of soil. After this, all cracks in the base are eliminated and waterproofing is installed. Protection from moisture can be carried out using a coating method, for example, bitumen mastic or by gluing with waterproofing materials (optionally, roofing felt). Insulation is poured into the trench and a concrete screed is poured.

When is it better to insulate the base of a wooden house?

The optimal period for arranging foundation insulation is considered to be the beginning of construction work, when the walls have not been erected and the subfloors are not ready. But if thermal protection was not provided at the construction stage, then it can be done during the operation of the building.

If you have the opportunity to choose an insulation option, then it is better to go with the external one. According to experts, internal insulation shifts the dew point, and the foundation is easily exposed to external humidity and cold, which quickly destroy it.

The insulation layer in the basement creates increased dampness, which can be eliminated with additional ventilation, and this is an additional expense.

Another drawback of arranging the system from the inside is a noticeable reduction in the area of ​​the room.

Features of thermal insulation

Before installing an insulation system, the foundation of the building in use must be completely excavated. The surface is cleaned of soil and other contaminants, damage and cracks are eliminated.

It is important to protect the foundation from groundwater. To do this, waterproofing is performed.

Bitumen mastic, special deep penetration solutions, roofing felt, and liquid rubber are used as waterproofing materials.

Installation of insulation

For external thermal protection, foam boards or extruded polystyrene foam are most often used. The insulation is installed using special glue without organic solvents. Additionally, you can secure them using dowels with a wide head. After the glue has completely dried (about two days), the underground part of the foundation is backfilled.

The material is attached to the base in the same way. But in its upper part it is necessary to use non-flammable insulation, for example, mineral wool. So, slabs of expanded polystyrene or polystyrene foam, which are not highly fire resistant, are separated from the wooden structures of the building.

Reinforcement and cladding

A reinforcing mesh is installed on the surface of the insulation, which is embedded in the adhesive solution.

Then you can do the finishing touches. Artificial stone or brick, tiles, and decorative plaster are suitable for this.

Ventilated facades

If fibrous materials are used as insulation, after its installation it is necessary to lay a vapor barrier layer. After that, a sheathing is installed, on top of which the facing material is attached.

Thus, a ventilation gap is formed between the thermal insulation and the finishing, due to which moisture does not accumulate in the insulation and it does not lose its properties.

Conclusion

Insulating the foundation of a wooden house is not an easy task, but the result is worth the effort. To ensure that money and time are not wasted, it is necessary to choose the right material depending on the type of foundation, climatic conditions of the area and financial capabilities.

Important! The required quantity and the total cost of the work performed depend on the degree of efficiency of the heat insulator.

Before insulating the foundation of a wooden house, it is important to calculate heating costs and the degree of thermal insulation required.

The most popular option is foam insulation. The method is cheap and quite effective. But the flammability of the insulation forces us to take fire safety measures. Mineral wool also retains heat well, does not burn, but is afraid of moisture, so without proper hydro- and vapor barrier, all work may be useless. Polyurethane foam is an excellent heat insulator, but it is expensive and its installation is possible only with the help of special equipment. In general, there are many options, you just have to choose which one suits you best.

Insulating the foundation allows you to reduce heat losses and improve the microclimate in the interior. The work can be carried out both at the stage of foundation construction (the best option) and on an already operating building. Let us consider in detail the algorithm for performing work in each case. Foundations can be insulated with expanded clay - an old and ineffective technology; heat saving indicators do not meet modern requirements. Today, various polymers are used for these purposes - cheap, durable and high-quality materials.

Material. Important Notes and Illustrations	Characteristics
	Thermal conductivity is 0.037 W/m2K. For a more clear understanding of this value, we point out that the thermal conductivity of wood is 0.12 W/m2K, expanded clay 0.14 W/m2K, and brick 0.7 W/m2K. As you can see, in this indicator it exceeds the specified materials by several orders of magnitude. It is second only to air, whose thermal conductivity is 0.027 W/m2K. Waterproof. The material does not absorb moisture and does not change its physical characteristics during prolonged direct contact with water. Index vapor permeability is less than 1% of the speed of vapor movement in the air; such indicators are ignored during practical calculations.
	Brand PSB-S 15 (GOST-15588-86). Density, kg/cub.m 11-15. Compressive strength at 10% linear deformation, MPa, not less than 0.05. Bending strength, MPa, not less than 0.07. Thermal conductivity in a dry state at 25±5 °C, W / (m×K) no more than 0.037. Humidity of slabs, %, no more than 1. Self-burning time, sec, no more than 3. Water absorption in 24 hours, %, no more than 1.
	Material density (kg/m3) from 28 to 45. Thermal conductivity coefficient (W/(m °K) 0.030 at 250 C. Fire safety category from G1 to G4. Vapor permeability coefficient 0.007 – 0.008 (mg/m·h·Pa). Compressive strength at 10% linear deformation 0.2 – 0.5 MPa (kgf/cm²; t/m²). Standard dimensions: width 600 (mm); length 1200 – 2400 (mm); thickness 30 – 100 (mm); Temperature range of use -50…+75 (°C).

The disadvantage is rather low strength indicators, but they are easily compensated for by the use of special technologies for laying the material.

Important. In all cases, insulation of the external surfaces of the foundation with polystyrene foam should prevent contact of the material with the ground.

1. Firstly, this will make the load on the area of ​​polystyrene foam plates uniform and will prevent damage to their integrity.
2. Secondly, sand compensates for the compression forces of the earth during freezing, which will also protect the insulation from mechanical damage.

You can replace sand with other durable and moisture-resistant materials, but this will cost much more and the overall effect will be less. Using other materials can only reduce the overall amount of work.

Most often the material is used for interior work, but in some cases it can also be used to insulate strip foundations. It occupies a leading position in terms of heat conservation; such indicators are achieved by increasing the number of air chambers. But it is the large presence of cameras that negatively affects physical strength indicators. In addition, polystyrene foam is afraid of harsh ultraviolet radiation and cannot be in contact with water for a long time.

The “brother” of expanded polystyrene. The differences are the best in terms of thermal conductivity, but the worst in terms of physical strength. Most often used in the industrial construction of buildings and structures for various purposes.

Modern construction technologies and innovative materials make it possible to achieve high efficiency of work at relatively low financial costs. There are several methods of foundation insulation using various materials; the specific choice of method should be chosen taking into account the type of foundation and the characteristics of the building.

Insulation with polystyrene foam boards

Let's consider the option of building a strip foundation with wooden formwork. Insulation work begins after the formwork is removed.

Step 1. Check the linearity of the side surface of the foundation. In most cases it will have to be leveled. Concrete seams will definitely appear between the joints of the boards and loose boards; they need to be cut down. In addition, large bulges should be corrected; the size of the bulges cannot exceed 0.5 cm per linear meter. Such irregularities allow the slabs to bend without mechanical damage and are partially eliminated by changing the thickness of the glue. Large irregularities cause a significant increase in material consumption, and it is quite expensive. Check the linearity of the surfaces with a flat strip or rope stretched at the corners.

Step 2. Take measurements of the foundation and draw up a rough plan for cutting materials. A very important operation, consider several options and choose the most optimal one. The cutting map will help to significantly reduce the amount of irretrievable waste, reduce the number of seams and speed up the work.

Step 3. Laying polystyrene foam boards.

It’s more difficult here; it’s very difficult to give general universal advice. The fact is that the slabs must be adjacent to the foundation over the entire area; air pockets cannot be left. In the case of insulating ceilings or walls, the glue does not need to be applied to the entire surface of the polystyrene foam; it will stick as it is, and the finishing lining will protect it from mechanical damage.

When insulating the foundation, this method is ineffective. There are two ways to level the foundation surfaces: by additional plastering or by increasing the thickness of the glue. The first method is more labor-intensive, but less expensive. The second method, on the contrary, requires less time, but more money to purchase expensive glue. Make your decision on the spot, taking into account both the condition of the foundation surfaces, your professionalism and the thickness of your wallet.

Step 4. Place polystyrene foam boards in rows according to a previously drawn up cutting map. Control their position using a long level or a level rod. The technology of gluing the slabs itself should not create difficulties; these are not ceramic tiles; millimeter precision is not required. Follow the recommendations of the glue manufacturers exactly; its consistency should not be too liquid or too thick.

You only need to press the plates with your hands. In order to slightly correct their position, you need to make small rhythmic movements with the plate up/down or left/right. The plates should fit as closely as possible to each other.

In most cases, the height of the underground part of the foundation is not the same, this is explained by the characteristics of the landscape. It is desirable that the visible top sheets of insulation are level; it is recommended to level the first bottom row. To do this, before starting work, you need to beat off a horizontal line at the lower edge of the foundation, and cut each slab at the required angle. This way you will be able to bring the edge of the insulation through the row into a horizontal position.

Step 5. Glue the slabs along the entire perimeter of the foundation, check the adhesion strength.

All wide seams between the slabs must be sealed with mounting or construction foam. There will definitely be seams; it is unlikely that you will be able to make the surface of the foundation absolutely flat. But this is not considered a defect; construction foam has excellent performance qualities.

Step 6. Carefully fill the trench with pitch. If the soil on your site is sandy loam, you don’t need to pour sand. If for one reason or another there are difficulties with the delivery of sand, this is not a problem. Take a metal mesh with a mesh size of approximately 1÷2 centimeters and sift the available soil. Large stones will be removed, and the sifted earth will not damage the insulation.

Insulation of a new foundation

Now let's look at a new technology for insulating the foundation through the use of permanent formwork

Insulation of foundations with permanent formwork - photo

This method has many advantages and only two disadvantages.

1. The first drawback is that formwork can be used for the construction of foundations only for low-rise wooden buildings. The load-bearing characteristics of the structure do not allow the method to be used for brick buildings.
2. The second disadvantage is that the cost of foundation work can increase up to 30%.

Permanent formwork consists of hollow blocks made of polystyrene foam.

Fixed formwork - photo Permanent formwork – corner block

The blocks are laid dry and fixed to each other using special tongue/groove mechanisms. The design features of permanent formwork make it possible to pour reinforced strip foundations. After the concrete has cooled, the trenches are backfilled and you have a ready-made insulated foundation. Moreover, not on one side, but on both sides, the efficiency of insulation, accordingly, doubles. The wall thickness of foam blocks varies widely; choose the optimal values ​​taking into account the specific features of the foundation. If you correctly follow the recommendations of permanent formwork manufacturers, the external and internal surfaces will be of high quality. There will be no need to foam any seams for one simple reason - there won’t be any.

Video - Video guide for installing permanent formwork

Video - Installation of permanent polystyrene formwork

A more complex case requires a significant amount of excavation work to be done manually. We will use polystyrene foam boards as insulation. We recommend using polystyrene foam for all types of insulation; among all its “brothers” it has the highest physical strength. The thermal conductivity of polystyrene foam is slightly higher, but the difference is so insignificant that it does not have any noticeable effect.

Step 1. Assess the condition of the facility, think through issues with temporary storage of land. The work will continue for several days and there may be heavy rains. If problems with the ground and temporary drainage of rainwater are not thought through in advance, then flooding along the perimeter of the dug trench is inevitable. And this is very dangerous, waterlogged soil under the foundation strip sharply reduces its load-bearing capacity, the consequences can be extremely unpleasant.

Step 2. Remove the tiles around the house or dismantle the concrete blind area. It is much easier with tiles, but the blind area will have to be cut with a grinder and a diamond blade. Work with an angle grinder very carefully; it is one of the most dangerous tools. Moreover, his injuries were severe. Be prepared that while sawing the blind area there will be a huge amount of dust: close the windows in the house, if the facades have decorative plaster or are covered with wooden clapboard, then it is better to cover them with film.

Step 3. Start digging a trench; the width of the trench should allow you to freely “handle” the shovel. If you do not remember the depth of the foundation, you will have to make a “test hole” and evaluate the condition and size of the foundation. This will help you draw up an optimal work plan and calculate the required amount of materials. Sometimes foundation strips are poured without formwork in the ground; the surface of the foundation is very uneven and it is not possible to correct it. In this case, there is an old method - insulation with expanded clay. The work is significantly simplified and cheaper, but the insulation efficiency is low.

An example of a excavated pit near the foundation

Expanded clay needs to be poured into a trench along the entire perimeter of the building, pour 10 centimeters of sand on top and restore the original appearance of the blind area on it.

Important. The fresh part of the blind area will definitely sag and become slightly lower than the old one.

There are three ways to solve the problem.

Step 4. If the foundation walls are suitable for insulation with polystyrene foam, great. Let the surfaces dry a little, once dry, take a wire brush and carefully remove all remaining soil. Keep in mind that in the place where dirt remains, the glue will not hold the insulation.

Step 5. If possible, remove any large projections. Working in a narrow trench is inconvenient, but you will have to work hard. Small ones can be cut down with a chisel; for larger ones, you need to take a hammer drill.

Step 6. Place the polystyrene foam boards on the glue, and check their position with a straight edge. The lath must simultaneously overlap at least two slabs, so you can place several insulation slabs in the same plane. If there are gaps, don’t worry, they are perfectly foamed with construction foam.

Step 7 Backfill the trench. Do not pour the entire layer of soil at once, carry out the work in stages. In order to reduce the inevitable shrinkage of fresh soil, it must be compacted. You will not be able to compact the soil to a depth of more than 20–25 centimeters using improvised “pushes” and your own feet. Accordingly, this thickness of fresh soil must be added after compacting the previous one. It may take more time, but then you will have fewer problems.

There is also such an option for carrying out the work; it can be used if the surfaces are very uneven, but you still want to insulate. For such insulation, you will have to seek the services of specialized companies, and only do the preparatory, excavation and finishing work yourself.

The better you prepare the surfaces, the more thoroughly you clean them of dirt, the more durable and effective the foundation insulation will be.

The company’s services will cost you a lot, you should immediately keep this in mind; resort to this method of insulation only in cases of extreme necessity. The surface of liquid polystyrene foam must be insulated from moisture; liquid rubber is used for this purpose. It provides reliable water protection for surfaces of any shape, but it will also cost a pretty penny. After insulating the foundation, excavation work is carried out similarly to those described above.

Waterproofing after insulation - example

	Values	Indicators and characteristics of sprayed polyurethane foam	Values
Thermal conductivity coefficient, W/MK	0,019-0,03	Cost of material, rub./m3	5500 rub. (material + work)
Coating thickness (Novosibirsk), mm	100-150 mm	Coating thickness, mm	100-150 mm
Adhesion to brick, concrete, metal, wood, kg/cm2	1.5-3 kg/cm2	Availability of additional fasteners	-
Bridges of cold	No	Presence of sheathing	-
Presence of vapor permeability layer,* mg/(m h Pa)	0,1-0,5	Availability of vapor barrier	-
Water absorption by mass,%	1	Ecological cleanliness	Safe
Work performance, ºС	+5С /+30 ºС	Moisture	Stable
Application temperature, ºС	-180...+100	Aggressive environments	Stable
Moisture, aggressive environments	Stable	Microorganisms, rodents	Stable
Shrinkage during use	-	Presence of phenol, formaldehyde, % by weight	-
Effective service life, years	25-50 years	Presence of fibers in the air	-
Flammability group	G1, G2	Presence of ozone-depleting gases	-
Actual heat loss	1.7 times lower than the normative SNiP 2.04.14-88 Energy Saving No. 1, 1999	Reliability	Work related to spraying polyurethane foam is carried out using modern equipment designed for these purposes. All stages of work are carried out by professionals who have all the necessary knowledge, so the possibility of defects is practically excluded.

Often in villages you can find old houses that have no foundation in the modern sense of the word. The log houses were placed on several stones, slightly dug into the ground. Over time, such houses sagged and leaned, and one or more of the lower rows of the frame rotted. By the way, all bathhouses were built using this “simplified method” at that time. Is it possible to insulate the foundation of such a house and how to do it?

First of all, the house needs to be jacked up and the rotten rows of the frame replaced. These works are complex; only real masters should undertake them. We will tell you what to do next with the foundation at the end of the article.

The work shown in the next photo can hardly be called foundation insulation.

It's more like patching holes with construction foam. How they will affect the improvement of the building’s heat saving performance, we do not undertake to judge. But we can say with confidence that the tree under the foam will rot at twice the speed.

Conclusion

Unfortunately, in this article we are forced to urge readers to carefully analyze the information available on the Internet. Let's give a few examples of “harmful” information that cannot be kept silent about.

Example 1. Almost all articles on the topic of foundation insulation, among numerous recommendations, propose to insulate absolutely all buildings, including wooden ones.

Why shouldn't this be done? Everything is very simple, the vast majority of buildings have wooden floor beams, joists and boards, and log houses are all built according to this rule. To prevent premature deterioration of wooden structures, construction standards not only recommend, they categorically oblige the installation of ventilation ducts in the foundation.

State regulations specify in detail the minimum frequency of air changes in the underground, and provide calculations for the size of the vents and their specific location. Insulating foundations in order to reduce thermal energy losses through floor coverings is possible only in one case: all floors are made on a concrete screed, and ventilation is not carried out through the basement part of the foundation.

The question is, why insulate the foundation in such houses if there must be constant drafts under the flooring? Or close the vents and completely change all the floor elements in a few years? The result of such work can only be a waste of time and money and fair ridicule from knowledgeable people.

Example 2. Cold foundations cause a loss of 10÷15% of thermal energy. Very strange, to put it mildly, calculations. Proving their complete absurdity is a waste of time.

Example 3. Warm foundations are needed for basements, but for which basements it is not specified. If basements are used to store food products, then there is no need to insulate anything. The optimal temperature for storing vegetables is ≈+5°; the foundation in houses with basements has a depth of about two meters, they are always relatively warm. The top slab, although slightly, heats up through the floor coverings. The question is, is there even the slightest risk that cucumbers in a jar will turn into “lollipops in a jar” in winter? Answer: yes, but you need to have a house far beyond the Arctic Circle, where there is permafrost.

Insulate the foundations only of those basements in which people stay for a long time; they can be different in purpose. And that insulation should be done not outside, but inside the foundation. Internal insulation allows you to speed up the time it takes to warm up the room to comfortable temperatures.

And finally, how to insulate the foundation of an old wooden house? No way, raise the house, replace the rotten wooden structures with new ones, if possible strengthen and level the existing foundation and carefully lower the building to its original place. If you also treat the lumber with antiseptics, then the safety of the house will last not only for your lifetime, but also for the lifetime of your children.

Video -