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.

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.

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

Thermal insulation around the perimeter

Before insulating the foundation around the perimeter, you need to remove the soil along the entire base of the building to a depth of about half a meter and a width of about one and a half meters. After creating the trench, approximately 20 cm of sand is poured in and it is thoroughly compacted.

Expanded polystyrene slabs are installed on the “sand cushion”. For additional reliability, insulating materials are attached using special adhesives, for example, bitumen mastic. The joints formed between the plates are blown out with foam. You can also fill the gaps using cold-applied bitumen mastic.

After fixing the insulation and completing the remaining related work, sand is again filled with a layer of at least 3 m.

Corner areas of buildings lose more heat than flat surfaces. Therefore, in these places you should use a larger (one and a half times) layer of polystyrene foam.

The advantages of perimeter insulation with expanded polystyrene foam are as follows:

• the design of the insulated foundation is protected from deformations and cracks;
• the basement is also thermally insulated;
• polystyrene foam has good performance properties, which makes it a fairly durable material.

Expanded polystyrene can also be used for internal insulation of an old house if external insulation is not possible. To do this, the inside walls are covered with foam boards. A room insulated in this way can become a full-fledged room.

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.

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.

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.

Follow manufacturer's instructions

Before insulating the foundation with your own hands, you need to study the instructions or consult with a specialist. If it is recommended to use a protective layer of foil with dimples between the insulation and the ground, it is better to lay it down. If the manufacturer says that there is no such need, you don’t need to do it!

The money will be wasted. Also, you should not make a reinforced layer of putty and mesh on the foundation walls, under the insulation.

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

Use suitable glue

Good thermal insulation must be well attached to the wall. A common mistake is using the wrong glue.

It is known that both polystyrene and styrodur are not resistant to solvents.

• Not knowing the chemical composition of cementitious materials, many people buy cement adhesive for fear of damage to the insulation.
• Thus, they damage the waterproofing layers!
• Therefore, you need to use the glue recommended by the manufacturer for application.

It is worth paying attention that insulating boards cannot be fastened mechanically, as the studs can damage the waterproofing.

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

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.

Using polyurethane foam as insulation

It is also possible to insulate the foundation from the outside using the technology of treating the walls of the base of the house by applying polyurethane foam to them. It is possible to carry out such work only at a temperature of 10 degrees above zero, however, this material is not only thermal insulation, but also simultaneously performs waterproofing functions.

Insulation of the foundation from the outside with polyurethane foam

All work is carried out in four stages:

1. Treatment of the foundation surface (cleaning from dirt, dust, etc.).
2. Application of polyurethane foam. Now, unfortunately, this work can only be performed by narrow specialists using specialized equipment.
3. Plastering the surface.
4. Filling the trench and installing a blind area.

The remarkable thing about this technology is that it saves time and eliminates the need to carry out various types of waterproofing work.