Insulating the foundation of a house from the outside: the best way to protect the foundation of the building

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Thermal protection is an important task that must be completed in order to reliably protect the box from the negative effects of atmospheric forces, and create a favorable microclimate inside the house. Insulation of the foundation of a house from the outside is most often carried out using polystyrene foam or other insulation materials. Sometimes a combination of technologies is used for more reliable protection. When choosing a material, it is important to take into account all environmental conditions.

Insulating the foundation from the outside allows you to protect the building and create an optimal microclimate inside

Why insulate the foundation base from the outside?

The base and foundation are considered the most vulnerable parts of any building, because it is these structures that bear the greatest load exerted by load-bearing walls and ceilings. Due to the fact that this part of the house is located below the surface of the earth, it is constantly exposed to moisture and freezing.

It is necessary to insulate the basement in order to protect the house as much as possible from freezing and humidity

Helpful advice! Insulation of the foundation and blind area is a task aimed at maximizing the strength and durability of structures, on which the service life of the building itself ultimately depends.

The basement is a continuation of the foundation, rising above the surface of the earth, which then goes into the external walls of the building. In other words, this part of the building is a connecting element of the foundation and load-bearing walls starting from the floor level on the first floor. It is the base that protects the building from high humidity and cold, and thanks to the presence of the base, the house has a more attractive appearance.

First of all, it should be noted that insulation materials must provide comprehensive thermal insulation of both the basement wall (basement) and the blind area around the building. Otherwise, it will be wrong to talk about the effectiveness of such measures. Theoretically, it is possible to insulate the foundation from the inside and outside, but the effectiveness of each method will be different.

Internal waterproofing and insulation of the foundation will help to insulate the room from the penetration of cold, but in this case, condensation will accumulate in the space between the wall and the insulation, which has a detrimental effect on the walls. In addition, when insulating the foundation from inside the house, the base will not be protected from frost. As a result, cracks may appear and slowly expand, which will ultimately cause a decrease in the strength characteristics of the building.

The strength and service life of the building will depend on the insulation of the foundation.

Insulating the foundation from the outside allows you to protect the basement and the material from which the base is made from freezing. The dew point also shifts towards the insulating material, which is considered more resistant to humidity and low temperatures than the base itself. The result of the work is a warm basement and a longer period of operation of the supporting structure. It is better to carry out such work at the construction stage. If you do this after construction is completed, the task will be much more difficult.

Before insulating the foundation of a house, you need to familiarize yourself with the conditions when work may not be necessary. For example, if this is a small country house intended only for summer use, you can skip this stage of construction. Other situations when you can neglect performing external work and limit yourself only to floor insulation:

• with a low base - up to 0.5 m;
• It is not always necessary to insulate a shallow foundation;
• if the building is located in favorable climatic conditions with no harsh winters.

Requirements for insulation

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.

The material for foundation insulation must meet a number of requirements

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.

The photo shows an insulated foundation

Insulating the foundation of a house from the outside: main advantages

A massive reinforced concrete foundation without thermal insulation on the outside will always be a powerful cooling accumulator in winter, as a result of which the cold will spread to neighboring building structures. Obviously, the floor level in ground floor rooms is usually located above the basement, and the walls and ceilings have their own insulation. However, such proximity always leads to excessive heat losses and, consequently, to additional costs for energy used for heating. Practice shows that the optimal material for insulating the foundation base provides up to 20-25% heat savings, regardless of other conditions.

Houses with an insulated foundation consume up to 25% less energy for heating than non-insulated buildings

The first important argument in favor of insulating the foundation of a house is to prevent heat leakage from the building. High-quality insulation of basement walls and blind areas around the house significantly reduces (almost to 0 °C) the effects of winter soil swelling. The reason is simple: the soil near the basement and under the house simply does not freeze.

All regions have their own indicators of soil freezing depth, which depend on climatic characteristics. Below this limit, the temperature is kept relatively constant due to the constant flow of geothermal heat from below. If you do not insulate the foundation of a private house, the base of the walls will not be able to stop the spread of soil freezing. As a result, not only the upper part of the foundation itself freezes, but also a strip of earth along the inside of the strip.

Important! After the foundation of the house is insulated, the freezing zone does not reach the ground or foundation walls, which will protect them from premature destruction.

All high-quality reinforced concrete foundations are characterized by a certain frost resistance. For example, a properly prepared M300 cement mortar usually has a frost resistance of F200, that is, it can withstand up to 200 freezing and thawing cycles without losing its basic characteristics. However, one should not think that one cycle is equal to one year. Several dozen such cycles can occur in one season, given the unstable autumn or spring weather. And this, in turn, means that it is best to take measures to avoid exposure to temperature changes on the foundation, that is, to insulate the foundation of the house.

An insulated building is more frost-resistant, which affects its durability

Why is it necessary to insulate the foundation?

From 15 to 20% of the heat escapes through the foundation. It is impossible to get rid of the problem by thermally insulating the basement separately. In addition, insulating the foundation will help get rid of the following problems:

• destruction of the base, since materials exposed to low temperatures quickly lose their quality characteristics;
• excessively cold floors on the lower floor;
• dampness in the basement, which contributes to the development of fungus and mold, which subsequently spread to the walls of the house.

Reliable thermal insulation and waterproofing makes it possible not only to provide a comfortable atmosphere in the house, but also to extend its service life.

How to finish the foundation of a private house

If thermal insulation is installed, the freezing zone does not penetrate into the house and does not reach the foundation wall. And this immediately gives many advantages. The entire height of the strip foundation - from the bottom to the top of the basement - will be in approximately the same temperature conditions. This means that the reinforced concrete structure will not have strong internal stresses, which are often caused by significant thermal disturbances. The lack of insulation of the strip foundation becomes one of the reasons for the rapid wear and tear of the building.

How to insulate the foundation? Until recently, a mixture of clay and straw was used to insulate the basement, but over the past few decades, technology has improved. A large number of new thermal insulation materials have been developed, which are characterized by a convenient shape and ease of installation. All modern materials must meet the following requirements:

1. Low thermal conductivity. The lower the thermal conductivity coefficient, the better the thermal insulation properties of the building material.
2. Low level of water absorption. Insulation that is susceptible to moisture absorption does not fulfill the requirements assigned to it and loses its consumer qualities. This is especially dangerous if the material absorbs moisture in winter, when freezing water disrupts the structure of the sheets.
3. High compressive strength. The soil exerts a lot of pressure on the base, which the insulation must endure without changing its properties.
4. Resistance to harmful microorganisms. Material that is susceptible to fungal growth and mold will quickly become unusable. Also, insulation sheets should not be exposed to rodents.

Quite often, expanded clay is used to insulate the outside of private houses.

The price of foundation insulation will depend on the working conditions, on whether the work is carried out during construction or already at the stage of its completion. The cost is also influenced by the type of material used, where the main ones are:

• sprayed insulation – polyurethane foam;
• thermal insulation sheets - polystyrene foam, penoplex, mineral wool, extruded polystyrene foam;
• expanded clay - an inexpensive, bulk type of thermal insulation;
• thermal panels - consist of three layers, including the finishing layer, where plaster or facing tiles are used;
• warm plaster;
• priming.

Thermal insulation during construction

The best way to properly and reliably insulate the entire foundation with penoplex is to do it yourself at the stage of building a house. In this case, special bitumen mastic is most often used to glue polystyrene foam boards to concrete. First, the surface is leveled with cement mortar, then cleaned and covered with the first layer of mastic (primer). Rolled waterproofing is glued onto it, and insulation is placed on top. The whole “pie” is shown in the diagram:

As can be seen in the diagram, an additional protective coating of geotextile can be laid on top of the thermal insulation layer, although often the penoplex is simply covered with soil. Additional protection will not require much expense, but will significantly extend the service life of the insulation. The technology for insulating foundations with expanded polystyrene using bitumen materials is shown in detail in the video:

Another interesting way to insulate the base of a house without a basement is used in cases where the foundation is a solid concrete slab. The essence of the method is that polystyrene foam is laid on a sand bed, and a monolithic concrete base is poured on top of it. In this case, it is possible to immediately install a heating circuit for heated floors inside the monolith. This design is called the Swedish stove; a diagram of its structure is shown in the figure:

Here you can see that the Swedish slab refers to shallow foundations, insulated not only from below, but also from the sides. In terms of energy efficiency, this technology is one of the best, but it requires a very scrupulous approach to the work. Failure to comply with technological requirements can lead to cracks in the slab and damage to the underfloor heating system.

The main disadvantage of the Swedish stove is the inability to carry out repairs in case of cracking. But if the insulation of the slab is laid correctly, then such a foundation will easily stand for several decades. At the same time, the use of a solid slab is possible on various subsidence soils. In practice, this insulated structure is often used to build wooden houses instead of a traditional strip foundation.

Insulating the foundation of a house from the outside with polystyrene foam

Insulating the foundation with polystyrene foam is considered one of the popular methods among builders that prevents freezing of the foundation. The base and foundation are covered with expanded polystyrene slabs, which are characterized by increased density; the thickness should not be less than 5 cm. Among the main advantages of insulating the foundation with expanded polystyrene are:

• high thermal insulation qualities and optimal thermal conductivity coefficient;
• inability to absorb moisture or degrade when exposed to water due to its closed cell structure;
• long period of operation - over 50 years;
• good sound and noise insulation properties;
• resistance to ignition due to the applied fire retardant;
• no possibility of mold or fungal growth;
• simple and quick installation of sheets, easy processing and the possibility of self-fixing without the use of special tools;
• low cost of material and its installation.

Expanded polystyrene as foundation insulation has a lot of positive qualities

If we talk about polystyrene foam, it is worth noting that it has a significant disadvantage - instability in front of rodents, which can damage the sheets. Disadvantages also include a large number of joints between sheets. Extruded polystyrene foam (penoplex) has slightly fewer negative characteristics, characterized by its smaller thickness but higher density.

Insulating the foundation and blind area of ​​a house from the outside with polystyrene foam is more effective than with conventional polystyrene foam, due to the interlocking system of joints, which ensures a more dense arrangement of sheets relative to each other. In addition, the material is characterized by less fragility, it does not crumble when cut and can withstand greater loads.

Helpful advice! Insulating the foundation of a house from the outside with penoplex provides a thinner layer of insulation without compromising the ability to retain heat. This makes it possible not to deepen the window openings so much, which will allow more sunlight to penetrate inside.

Extruded polystyrene boards have many different advantages, including lightness, high heat transfer resistance, ease of processing and installation (including due to the clear geometric shapes of the panels), environmental friendliness, durability and many others.

Expanded polystyrene has excellent thermal conductivity, as well as sound and sound insulation

When insulating the foundation of a house from the outside with your own hands using polystyrene foam, it is quite easy to calculate the required amount of material, especially if you have a building plan with the parameters necessary for vertical and horizontal basic insulation. The calculation is usually based on the standard dimensions of Penoplex boards (1200x600 mm) and the range of insulation thicknesses of Penoplex F panels developed specifically for foundations (in ml):

• 20;
• 40;
• 50;
• 60;
• 80;
• 100.

Polystyrene foam insulation technology

The cheapest and fastest way to insulate the foundation is to use polystyrene foam. To install it, you will need a minimum set of tools: a knife, a hammer drill, a construction mixer. You will also need to purchase glue for PPS, primer, plaster, construction mesh, and disc dowels.

The work is divided into several key stages:

• If the house has already been built, then its foundation will have to be dug up. To do this, a trench is made around the perimeter of the building about a meter wide and equal to the height of the foundation. Remains of soil are removed from surfaces. Leave for a week to allow the moisture to evaporate.
• Surfaces are primed with a latex-based composition. This will help protect cracks and cavities from moisture. For this purpose, you can use mastic.
• Expanded polystyrene sheets are attached using glue. You need to press them lightly with your hand so as not to damage the material. In areas of the foundation located above the ground level, the sheets are fixed with disc-shaped dowels. You will first have to drill holes for them using a hammer drill. The sheets are very light, so insulating the foundation of a house with expanded polystyrene from the outside can be done alone.
• The seams formed between the EPS boards are sealed with polyurethane foam or rubbed with glue.
• The last step is filling the trench with soil. The soil is thoroughly compacted.

PPS, which is located above ground level, does not look aesthetically pleasing, so it will have to be plastered. Before this, a construction mesh is placed on it. Drying time of the layer is 2 days.

What is foamed polyurethane foam, how is it used to insulate the foundation

Do-it-yourself insulation of the foundation of an already built house has recently become popular with the help of foamed polyurethane foam, which is characterized by excellent consumer qualities. The only disadvantage is the need to use a special installation during application, in which the polyol and isocyanate are mixed under pressure, after which the synthesis of the polymer begins. During the reaction, carbon dioxide is formed, which creates bubbles that are separate from each other. Spraying is carried out in a thin layer on a previously cleaned and prepared base.

Before insulating the foundation, it is recommended to familiarize yourself with the positive and negative qualities of the material:

Foamed polyurethane foam is used for insulation of already constructed buildings

1. Excellent thermal insulation properties, which are improved due to the presence of carbon dioxide bubbles, because the thermal conductivity coefficient of polyurethane foam is slightly lower than that of air.
2. Resistant to mold and fungal growth.
3. Continuity of the applied layer without gaps, joints, cracks or seams.
4. Light weight, which allows the solution to be used on houses with any type of foundation. At the same time, high strength, rigidity and elasticity.
5. Easy repair. If a certain area is damaged, it can be easily cleaned and filled with a new portion of polymer.
6. Quick application. Spray insulation takes no longer than one day to complete.

In addition to the need to use special means for application, the disadvantages include the high cost of the material and the inability to carry out the work independently.

How to organize water drainage from the base?

Melt and rain water lead to the destruction of the foundation over time. Often even proper insulation cannot save in such a situation. Therefore, it is important to organize the drainage of liquid from the base of the house. For this purpose, an open or closed drainage system is made.

The easiest way to do it yourself is open drainage. It consists of ditches about 0.5 meters wide and 1 m deep, dug along the entire perimeter of the building. The walls of such a trench are beveled at an angle of 30 degrees for better water drainage. Liquid from the pits should move to the drainage well. Therefore, the efficiency of such a system is much higher if the site has a slope.

Closed drainage has recently become the most popular. It consists of pipes that are dug into the ground outside the building around the perimeter. They are laid at an angle to allow water to flow independently into the drainage well. Pipes must be wrapped with geotextiles.

How mineral wool and warm plaster are used to insulate the foundation

Mineral wool refers to a whole range of building materials, but basalt wool is most often used to insulate the base or foundation. The starting raw materials are rocks, from which, in the process of heating and melting, thin threads are drawn out, which serve as the basis for the insulation. The material is produced in rolls or slabs. At the same time, the use of rolled mineral wool allows you to end up with a minimum number of seams, but the slabs are characterized by increased strength. The main advantages of using the material:

Warm plaster has both positive and negative properties

• optimal thermal conductivity coefficient ensured due to the presence of a fibrous structure;
• good sound insulation;
• low susceptibility to combustion, because the basis is mineral substances;
• high vapor permeability rates;
• increased strength and resistance to mechanical damage;
• resistance to mold, fungi and rodents.

Using mineral wool, you can easily and quickly insulate the foundation of a house from the outside with your own hands. Despite the fact that many manufacturers note the ability of the material to pass water and not absorb moisture, this is not entirely true. Sheets for the most part can accumulate moisture, and their thermal insulation properties are significantly reduced. To avoid this situation, some manufacturers add certain water-repellent substances to the material, but even in this case, reliable waterproofing is required, which will entail additional installation costs.

Related article:

Insulating the façade of a house from the outside: the best way to improve the microclimate inside the building

Main advantages. The main types of materials used, their brief characteristics, pros and cons. Laying technologies.

Warm plaster includes dry adhesive mixtures that are not similar to the facing material. Most often, the insulation composition includes sawdust, vermiculite and polystyrene foam. The main advantage of the application is the solidity of the heat insulator structure, as well as simple installation. Warm plaster can be used immediately after the preliminary primer layer has dried. If it is not necessary to apply two layers, then installation can be carried out without reinforcing mesh, which significantly reduces the cost of work. Among the disadvantages are:

• high level of water absorption, which requires waterproofing;
• a small layer of application, which cannot always provide the proper level of thermal insulation;
• heavy weight after use;
• the need for a finishing layer.

Mineral wool slabs are characterized by vapor permeability and sound insulation

Which insulation is more effective?

Each of the listed insulation materials has its own pros and cons. Moreover, they are all used for thermal insulation of the foundation. When choosing insulation you need to consider:

• temperature of the region;
• soil features;
• foundation type;
• required thickness of insulation.

According to statistics, the most common materials used for insulating foundations are slab and sprayed materials, but loose expanded clay and mineral wool insulation are less popular.

Use of expanded clay and thermal panels for foundation insulation

Expanded clay is considered a lightweight material with many large granules. The basis of the insulation is low-melting clay, which swells and hardens in a drum environment. Expanded clay is a safe and environmentally friendly material, characterized by the lowest cost. Suitable for insulating the foundation of a wooden house, which is not intended for year-round habitation. The main advantages of the purchase:

• good noise and heat insulation provided due to the porous structure;
• little weight;
• good frost resistance and fire resistance.

The main disadvantage of use is the ability to absorb moisture, which is unacceptable in the conditions of a basement or foundation. In order to solve this problem, good waterproofing is used, and drainage must be arranged by digging a ditch deeper than the foundation, at the bottom of which geotextiles are laid. Medium-sized crushed stone is poured on top of it, and a pipe is installed with holes through which moisture will be drained.

Then again there are layers of crushed stone and geotextiles, after which everything is covered with sand. After completing the preparatory work, wooden formwork is installed to the depth of the foundation and roofing material is laid so that it covers both the walls of the building and the walls of the ditch, and the seams are taped. Expanded clay of a heterogeneous fraction is poured into the formwork; after filling, it is closed with a lid, which is installed at an angle of 45°. This is done in order to protect the base from precipitation, including dew.

Thermal panels allow you to save on additional finishing materials

Thermal panels are based on rigid polyurethane foam, the positive properties of which do not differ from penoplex. The main advantage of use is the presence of a decorative top shell that can imitate any material. For the foundation and ground floor, imitation stone, brick or tile is most often used. The cost of insulating the foundation with this material varies from 2 thousand rubles per m², but due to the fact that the panels are completely ready for use, you can glue them on yourself. Other positive qualities:

• moisture resistance and good thermal insulation;
• attractive appearance;
• no risk of mold.

In addition to the high cost, the disadvantages also include the need to use high-quality and expensive adhesive, as well as special care when gluing. To glue the panels, you also need to have a perfectly flat base, or you will have to additionally install lathing, but the result will be an effectively protected base.

Helpful information! In some cases, ordinary sand or earth is used as a temporary material for insulation, which is used to fill the base up to the height of the floor on the first floor. However, you will have to move the ventilation holes above ground level, and installing windows will not be possible at all.

Expanded clay is considered the most cost-effective option for foundation insulation

Backfill method of insulation

Insulating the foundation from the outside with expanded clay does not reliably protect surfaces from moisture. The moisture absorption coefficient of this material reaches 20%, while for PPS it is about 4%. Expanded clay is several times cheaper, and therefore it continues to be used.

The installation process is divided into several stages:

• A trench at least half a meter wide is dug around the building.
• A layer of waterproofing film is laid on the bottom and walls of the resulting pit.
• Fill in expanded clay and level it.
• Cover the top with a layer of film.
• Pour a layer of sand.

The final stage is the installation of a blind area. This is additional protection of the foundation from low temperatures and moisture. In addition, it performs a decorative function.

Features of insulation of pile foundations, strip and slab foundations

The technology of insulating a foundation slab is similar to the thermal insulation of a concrete floor on the ground. To do this, first of all, the soil is compacted, on top of which a geomembrane is laid, protecting the foundation from the capillary rise of groundwater. Next are the following layers:

• crushed stone-sand cushion, which increases the load-bearing capacity of the soil and correctly distributes the load;
• roll waterproofing;
• insulation, most often used polystyrene foam or penoplex.

There is a large selection of technologies for insulating strip foundations. Along with insulating the outside of the foundation with penoplex, the technique of permanent formwork, application of sprayed insulation, or finishing with expanded clay is used. Mineral wool is rarely used in this case due to its ability to absorb moisture.

If you choose the permanent formwork method, then it must be planned at the construction stage, because the thermal insulation materials used to insulate the foundation are an integral part of the structure.

For different foundations it is advisable to use different types of insulation

This is interesting! When performing permanent formwork, two issues are simultaneously resolved - insulation of the foundation both from the outside and from the inside.

Formwork is made from various materials, but most often the foundation base is insulated from the outside with penoplex or expanded polystyrene. Before starting work, it is necessary to make a recess from the compacted soil for the blind area, which is then filled in turn with the following materials:

• crushed stone;
• sand;
• waterproofing;
• insulation;
• formwork;
• reinforcing layer;
• concrete.

Equally important is the insulation of the base from piles or pillars. Of course, with a properly designed foundation of this type, it is no longer threatened by freezing forces or the damaging effects of soil moisture. However, there are a number of other, no less important issues that can only be solved by creating thermal insulation.

Schematic example of insulation of a strip foundation

Reinforced concrete gratings or post piles require thermal insulation, which must be no less than the base of the strip. It is important to understand that piles are often connected to a monolithic reinforced concrete grid, which, without proper insulation, becomes a powerful refrigeration element. A characteristic feature of a foundation on piles is the presence of a gap between the ground and the ceiling of the first floor, where utilities are usually laid.

Insulation of a pile-screw foundation of a wooden house is most often accompanied by decorative finishing of this part of the facade. In any case, the space between the house and the ground will be closed on all sides and will not become a place for dirt or debris to accumulate. Measures to insulate a pile-screw foundation are also necessary to ensure comfortable living, increase the service life of the building and improve the appearance of the structure.

Video description

You can get acquainted with the features of polystyrene foam insulation technology in the video:

Insulation with sprayed polyurethane foam

Among all polymer insulation, sprayed polyurethane foam is the most expensive type. Its advantage is that the thermal insulation layer has no seams, and foamed polyurethane has very good adhesion to all types of building materials.

Application of polyurethane foam to a surface cleared of dirt is very quick. There are two types of materials: two-component and one-component.

In the first case, professional equipment is needed, the work of which is to supply both components under pressure to the working head, where they are mixed and foamed.

Single-component polyurethane foam is produced in liter aerosol cans, and even an untrained beginner can handle them correctly. But this technology is good for a small area of ​​work, or when it is necessary to apply a small layer up to 2 cm thick.

Spraying polyurethane foam is similar to painting with a spray gun, so it is better to cover the cladding of the house. Source ppuspb.ru

If the soils are dry, the water level is low and proper drainage work has been carried out, then waterproofing of the foundation and base need not be carried out - there are no seams, and the water absorption of hardened polyurethane foam is small (no more than 2%). When finishing the base with plaster, reinforcement is not necessary - there are no joints, like with foam plastic slabs, and, therefore, there are no prerequisites for cracks to occur.

In addition to the price, polyurethane foam has one more small drawback, which is a consequence of its advantage - good adhesion. When carrying out work on insulating the basement, it is necessary to protect walls that already have finishing (or do not require it) - this is easier than cleaning off hardened foam.

Insulation with expanded clay

Recently, this bulk material is rarely used for foundation insulation. Its use is limited by two factors: quite high, compared to polymer insulation, water absorption and thermal conductivity.

The thickness of bulk thermal insulation can reach 60 cm Source obustroeno.com

The first indicator lies in the range of 8-20% of the volume. Moreover, such water absorption is typical for “fresh” expanded clay - over time it becomes even higher. For comparison, for ordinary polystyrene it is no more than 4%. Therefore, waterproofing of both the foundation and the entire insulation layer is necessary.

It is impossible to ensure complete “tightness” of expanded clay, and it will take a long time to dry underground, wrapped in film - its use is not recommended in conditions of high seasonal rise of groundwater.

Thermal conductivity also does not meet modern requirements for thermal protection of buildings - 0.07–0.18 (W/m*°C) versus 0.02–0.04 for polyurethane foam, 0.03–0.04 for EPS/EPS. Therefore, the recommended thickness of bulk thermal insulation for our middle latitudes lies in the range of 40–60 cm.

The insulation scheme looks like this:

• dig a trench of the estimated width (or clear the cavity of the pit) to the heel of the foundation;
• lay a waterproofing film over the entire area of ​​the trench - foundation-bottom-wall;
• fill and level expanded clay;
• cover with film on top;
• pour a layer of sand;
• make a blind area.

Typical scheme for insulating a foundation with expanded clay Source sevparitet.ru
The advantage of expanded clay is its environmental friendliness and low price. Although, taking into account waterproofing and a large volume of materials, the cost of work in the end will not be so low. In addition, the base will have to be insulated using one of the above methods.

Do-it-yourself thermal insulation: step-by-step instructions

When doing the work yourself, step by step:

• Inspection and preparation of trenches, foundation surfaces or work sites are carried out.
  The bases, covered with insulation, are cleared of soil and debris, and, if necessary, strengthened and leveled. You may be interested to know how much it costs to dig a trench for a foundation and how to do it correctly manually and using an excavator. The areas under the future soles or cellar floor are compacted, covered with gravel, and covered with roll waterproofing.
• The main waterproofing layer of the foundation is being installed (it is skipped when insulating the PPU structure). Read about how to waterproof a foundation with your own hands here.
• Insulation boards are attached to clean and dry surfaces.
• The outer parts are facing, the soil is backfilled and the blind area is insulated (if necessary).

On a note. Important nuances of the technology include the need for adhesive fixation of underground areas, and mechanical or adhesive fixation of above-ground areas.

The layers filled with soil should be as solid and airtight as possible. To fulfill this requirement, slab types of insulation are installed in 2 or more layers.

Features of installation of thermal insulation made of polyurethane foam

If polyurethane foam is used to insulate the foundation of houses, then there is no need to first level the surface and cover it with waterproofing. It will be enough:

• Dig a trench.
• Clean the foundation from contamination.
• Dry.
• Inspect the base. If there are old pieces that are peeling off, they are removed and sealed.
• Then polyurethane foam is applied.

Everything dries out very quickly, so you can immediately begin arranging the blind area, and then the exterior finishing.

Installation of a foam insulation layer

Let's start insulating the foundation with penoplex by choosing the material. Penoplex slabs are available in two standard sizes: 0.6 m x 1.2 m and 0.6 m x 2.4 m. We do not give any specific decision on thickness - everything is purely individual and depends on the thickness of the wall and the material, from which it is folded.

Penoplex is glued to the base with a special glue; it is sold in bags in the form of a dry mixture. We will not dwell on glue brands - every self-respecting company producing dry mixes necessarily produces glue for penoplex foam.

1. While the mastic was drying, its surface was covered with dust, so we treated the waterproofing with a primer. The primer increases adhesion and improves the quality of gluing.
2. Apply an even layer of adhesive mixture to the foam board. We also apply glue to the wall. Press tightly. And so on until the entire surface is sealed.
3. At 4-5 points of each sheet we drill and hammer in additional fasteners - a dowel-fungus.

Note! With a planned insulation thickness of 10 cm, it is better to take twice as much material, but 5 cm thick, and glue it in two layers so that the slab of the second layer overlaps the joint of the first.

Decorative finishing of the outside of the foundation