House Foundation Insulation: The Best Way to Protect the Foundation of the Building

House Foundation Insulation: The Best Way to Protect the Foundation of the Building

Thermal protection is an important task that needs to be performed in order to reliably protect the box from the negative effects of atmospheric forces, and create a favorable micro-climate inside the house. House foundation insulation the outside is most often carried out with the help of expanded polystyrene or other heaters. Sometimes, for more reliable protection, a combination of technologies is used. When choosing a material, it is important to consider all environmental conditions.

Why carry out the insulation of the basement outside

The basement and foundation are considered the most vulnerable parts of any building, because it is precisely on these structures that the greatest load is placed on the 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.

protect the house as much as possible from freezing and humidity
The basement must be insulated in order to protect the house as much as possible from freezing and humidity

Useful advice! House foundation insulation and blind areas is a task aimed at maximizing the strength and durability of structures, on which the life of the building itself ultimately depends.

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

First of all, it should be noted that heaters should 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 events. 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 isolate the room from the penetration of cold, but in this case condensate will accumulate in the space between the wall and the insulation, which will have a detrimental effect on the walls. In addition, when warming the foundation from the inside of the house, the basement will not be protected from frost. As a result of this, cracks may appear and their slow expansion, which ultimately will cause a decrease in the strength characteristics of the building.

protect the house
The strength and life of the building will depend on the insulation of the foundation

House foundation insulation 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. To perform such work is better at the construction stage. If you do this after the construction is completed, it will be much more difficult to complete the task.

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

  • with a low base – up to 0.5 m;
  • it is not always necessary to warm a shallow foundation;
  • in case the building is located in favorable climatic conditions with no harsh winters.

House foundation insulation outside: the main advantages

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

House with a warmed foundation
Houses with a warmed foundation consume up to 25% less energy for heating than non-warmed buildings

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

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

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

All high-quality reinforced concrete foundations are characterized by a certain frost resistance. For example, a correctly 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 dozens of 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 the basis of temperature differences, that is, to insulate the foundation of the house.

How to finish the foundation of a private house

If thermal insulation is made, the freezing zone does not penetrate the house and does not reach the foundation wall. And this immediately gives many advantages. The entire height of the strip foundation – from the sole to the upper part of the basement – will be approximately at 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 deterioration of the building.

How to insulate the foundation? More recently, a mixture of clay and straw was used to warm 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 coefficient of thermal conductivity, the better the thermal insulation properties of the building material will differ.
  2. Low level of water absorption. A heater that is susceptible to moisture absorption does not fulfill the requirements imposed on it and loses its consumer qualities. This is especially dangerous if the material absorbs moisture in the winter, when freezing water violates the structure of the sheets.
  3. High compressive strength. The soil exerts a lot of pressure on the base, which the insulation must carry without changing the properties.
  4. Resistance to exposure to harmful microorganisms. Material subject to the growth of fungus, the appearance of mold, will quickly become worthless. Also, insulation sheets should not be exposed to rodents.

The price of insulation of the foundation 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 affected by the type of material used, where the main ones are:

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

House foundation insulation: the main advantages with polystyrene foam

House foundation insulation with foam among builders is considered one of the popular methods that prevents freezing of the base. The base and foundation are lined with expanded polystyrene plates, which are characterized by increased density, while the thickness should not be less than 5 cm. Among the main advantages of warming the foundation with expanded polystyrene, there are:

  • high thermal insulation qualities and optimal coefficient of thermal conductivity;
  • inability to absorb moisture or collapse under the influence of water due to a closed cellular structure;
  • long period of operation – over 50 years;
  • good sound and noise insulation properties;
  • resistance to ignition thanks to the applied flame retardant;
  • the lack of the possibility of mold or propagation of the fungus;
  • simple and quick installation of sheets, easy processing and the possibility of self-fixing without using a special tool;
  • low cost of material and its installation.
Expanded polystyrene is characterized by excellent thermal conductivity, as well as sound and noise insulation

If we talk about polystyrene foam, it is worth noting that it has a significant minus – instability in front of rodents, which can damage the sheets. The disadvantages also include a large number of joints between the sheets. Extruded polystyrene foam (polystyrene foam), which has a smaller thickness but a higher density, has slightly less negative characteristics.

Insulation of the foundation and the blinds of the house outside with expanded polystyrene is more effective than conventional foam, due to the castle joint system, which provides a denser arrangement of sheets relative to each other. In addition, the material is less fragile, it does not crumble when cut and can withstand a large load.

Useful advice! Warming the foundation of the house with foam outside 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 that it will allow more sunlight to penetrate inside.

Extruded polystyrene plates 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.

When warming the foundation of a house with a do-it-yourself penex, it is quite easy to calculate the required amount of material, especially if there is a floor plan with the parameters necessary for vertical and horizontal basic insulation. The calculation is usually based on the standard sizes of Penoplex boards (1200 × 600 mm) and in the range of insulation thickness of Penoplex F panels designed specifically for foundations (in ml):

  • 20;
  • 40;
  • 50;
  • 60;
  • 80;
  • one hundred.

What is foamed polyurethane foam, how is the foundation warmed by it

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

Foamed polyurethane
Foamed polyurethane foam is used to warm already built buildings

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

  1. Excellent thermal insulation properties, which are improved due to the presence of carbon dioxide bubbles, because the thermal conductivity of foamed 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 use of mortar on homes with any type of foundation. At the same time, high strength, rigidity and elasticity.
  5. Easy repair. If a certain area is damaged, it is easy to clean and fill it with a new portion of polymer.
  6. Fast application. Sprayable thermal insulation is carried out no longer than one day.

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

How is mineral wool and warm plaster used to warm the foundation

Mineral wool is a number of building materials, but basalt wool is most often used to warm the base or foundation. The raw materials are rocks, from which, during heating and melting, thin threads are drawn that serve as the basis of the insulation. Material is produced in rolls or slabs. At the same time, the use of rolled mineral wool allows you to get a minimum number of seams, but the plates are notable for their increased strength. The main advantages of using the material:

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

Using mineral wool, you can easily and quickly do the do-it-yourself warming of the foundation of the house outside. 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, while the insulating 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.

Warm plaster includes dry adhesive mixtures that are not similar to the facing material. Most often, the composition of the insulation includes sawdust, vermiculite and expanded polystyrene. The main advantage of the application is the monolithic construction of the heat insulator, as well as easy installation. The use of warm plaster is allowed immediately after the preliminary primer layer has dried. If two layers are not required, installation can be performed without a reinforcing mesh, which significantly reduces the cost of work. Among the disadvantages are:

  • high level of water absorption, which is why waterproofing is required;
  • a small coating layer, which can not always provide the proper level of thermal insulation;
  • heavy weight after application;
  • the need for a finish coat.

Use for warming the foundation of expanded clay and thermal panels

Expanded clay is considered a lightweight material having many large granules. The basis of the insulation is fusible 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 warming the foundation of a wooden house, which is not intended for year-round living of people. The main advantages of the acquisition:

  • good noise and heat insulation provided by 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 a basement or foundation. In order to solve this problem, good waterproofing is used, drainage is necessarily equipped by digging a ditch deeper than the foundation, on the bottom of which geotextiles are laid. On top of it crushed stone of medium size is poured, a pipe is installed with holes through which moisture will be removed.

Then again there are layers of rubble and geotextiles, after which everything is covered with sand. After the preparatory work is completed, a wooden formwork is mounted to the depth of the foundation and the roofing material is laid in such a way that it covers both the walls of the building and the walls of the ditch, while the seams are glued. Expanded clay expanded clay 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.

house foundation insulation1
Thermal panels allow you to save on additional finishing materials

Thermopanels are based on rigid polyurethane foam, the positive properties of which do not differ from foam. The main advantage of using it is the presence of a decorative upper shell, which can imitate any material. For the foundation and basement, imitation of stone, brick or tile is most often used. The cost of warming the foundation with this material varies from 28$ per m², but due to the fact that the panels are completely ready for use, you can stick them on your own. Other positive qualities:

  • moisture resistance and good thermal insulation;
  • attractive appearance;
  • lack of likelihood of mold.

In addition to the high cost, the disadvantages also include the need to use high-quality and expensive adhesives, as well as special care when gluing. For gluing the panels, it is also necessary to have a perfectly flat base or you will have to install an additional crate, but the result is an effectively protected base.

Useful information! In some cases, ordinary sand or earth is used as temporary material for warming, with which the base is covered up to the height of the floor on the ground floor. However, it will be necessary to remove the vents above ground level, and install windows will not work at all.

Features of insulation of the pile foundation, strip and slab foundation

The insulation of the foundation slab according to technology resembles the performance of thermal insulation of a concrete floor on the ground. To do this, first of all, soil is rammed, on top of which a geomembrane is laid, which protects the foundation from the capillary rise of groundwater. Next are these layers:

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

To warm the strip foundation, there is a wide selection of technologies. Along with insulation from the outside of the foundation with foam, the method of fixed formwork, spraying insulation or expanded clay finish is used. Mineral wool in this case is rarely used due to its ability to absorb moisture.

If you choose the method of fixed formwork, then you need to plan it at the construction stage, because the heat-insulating materials used to warm the foundation are an integral part of the design.

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

It is interesting! When performing fixed formwork, two issues are simultaneously solved – insulation of the foundation both from the outside and from the inside.

The formwork is made of various materials, but most often the basement base is insulated with foam or polystyrene foam on the outside. Before starting work, it is required to make a recess for the blind area from the compacted soil, which is further filled in turn with the following materials:

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

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

Reinforced concrete gratings or pole piles require thermal insulation, which should be no less than the base of the strip. It is important to understand that piles are often connected with a monolithic reinforced concrete grating, which without proper insulation becomes a powerful cooling element. A characteristic feature of the foundation on piles is the presence of a gap between the ground and the overlap of the first floor, where engineering communications are usually laid.

Warming of the pile-screw foundation of a wooden house is most often accompanied by decorative decoration 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 of accumulation of dirt or debris. Measures to warm the pile-screw foundation are also necessary to ensure a comfortable stay, increase the service life of the building and improve the appearance of the structure.

The technology of warming the foundation with Penoplex

This technology can be used with an already completed foundation, so it can be carried out both at the construction stage and during repair. If you perform work after the construction of the building, you will need to dig out and completely clean the base. After this, it is absolutely necessary to create reliable waterproofing with the help of a bitumen primer, onto which then strips of rolled materials overlapped are mounted from bottom to top.

Penoplex insulation
Penoplex insulation can be carried out both at the construction stage and at the finished house

After waterproofing, installation of thermal insulation materials continues. When doing foam-rubber insulation of a foundation covered with waterproofing with your own hands, various methods and materials can be used. It is best to buy a special adhesive designed for thermal insulation work. The extruded polystyrene foam sheet holds well on a vertical surface.

Important! Work always starts from the bottom – from the base of the foundation. If the shape of the base is complex, that is, there are several transitions from vertical to horizontal, it is advisable to repeat the entire configuration using insulation. To minimize the gaps between the material, it is necessary to stick the sheets as close as possible.

To minimize the possibility of moving sheets as a result of soil pressure, it is imperative that the sheets be fixed using dowels and umbrellas when warming the foundation of the house with foam. Mounting holes are drilled in the base directly through insulating boards already installed on the adhesive solution. The diameter and depth of the hole directly depends on the thickness of the insulation, wall material and the model of the selected dowels.

It is generally believed that the expansion part of the dowel enters the foundation wall by 45-60 mm. The number of these elements on a standard plate is 5-6. After the holes have been prepared, the dowels are inserted into them so that the caps rest on the insulating panel, and then expansion gaskets are driven in (depending on the specific model of fasteners). If based on the results of thermal engineering calculations it is established that two-layer insulation is required, then the second row of heat-insulating plates is mounted on the first so that the seams between the blocks are displaced.

At the last stage of the basement base insulation warming, a glutinous solution is applied with foam, then a reinforcing fiberglass mesh is attached, which is then plastered and finished with the selected facing material.

House foundation insulation is an important task that helps to extend the life of the foundation, respectively, and the entire building. The choice of insulation and the method of work depend not only on the material from which the foundation is made, but also on environmental conditions, for example, on the proximity of groundwater, such as soil and climate. Insulation of the foundation will be effective only if it is part of the general “set” of thermal insulation of the recessed foundation, the soil around the perimeter of the building, the floor of the first floor and the facade wall. There should be no gaps between the components of the entire system, otherwise the heat will constantly come out.


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