Insulation of the foundation: how to do it right for many years?

Insulation of the foundation is an important stage in the thermal insulation of a house, and also serves to protect the base from freezing and destruction. It is better to carry out thermal insulation during the construction phase, however, if necessary, it can be done in an already built facility.

Insulation of the foundation allows you to prevent the negative impact of the external environment on it, which increases its service life, and therefore the period of operation of the entire structure.

A large percentage of the heat loss of an object falls on an uninsulated foundation, even if its walls and roof are properly insulated. With heat loss, additional heating sources have to be activated, which leads to an increase in the cost of housekeeping. But the most important thing is that excessively heated air becomes dry. It is uncomfortable and unhelpful to be in such a room.

Mandatory insulation is meant in those basements and basements that are used as boiler rooms, swimming pools, billiard rooms, etc. It is clear that in the operated plinths, the lack of heat makes it impossible to use the room. When located in the basement of communications, it is also important to ensure the proper level of temperature indicators, otherwise their failure cannot be avoided.

It is also customary to insulate the pile foundation to reduce heat loss at floor level. For this, the basement part is insulated, taking care to prevent the formation of "cold bridges" between metal and other elements.

Thermal insulation of the base allows you to avoid swelling of the soil, since the latter does not freeze around the foundation. This, in turn, helps to avoid soil vibrations that cause shrinkage and subsidence of the foundation, violation of its geometry.

As you know, each type of foundation has a certain frost resistance. For concrete substrates, the average is 2000 cycles. This means that the structure can withstand up to 2000 freeze and thaw cycles without losing its technical performance. At first glance, the figure is quite impressive. However, in practice, in one winter, several tens of freezing and defrosting cycles can occur, which, naturally, reduces the durability of the base.

The use of thermal insulation materials reduces the number of freeze / thaw cycles, since the foundation does not have time to freeze. As a result, the total number of permissible cycles is "spent" less actively, and therefore the foundation will last longer.

Insulation of the foundation of a private house or other object is carried out in conjunction with waterproofing, which allows you to extend the service life of the structure, strengthen it, and protect it from the negative effects of groundwater and atmospheric phenomena.

There are a considerable number of insulation methods, but first of all, it is worth deciding whether the insulation will be external or internal.It should be noted right away that experts recommend carrying out thermal insulation from the outside, since this is a more effective method.

It is the outer thermal insulation that allows the maximum (by 20-25%) to reduce heat loss, as well as to protect the base. With internal thermal insulation, surfaces do not accumulate heat, therefore, tangible heat loss occurs. In addition, the surface that is not insulated from the outside freezes more (since it does not have contact with a warmer basement or basement) and, accordingly, collapses faster.

With internal insulation, it becomes almost impossible to reduce soil freezing and prevent heaving. In addition, groundwater continues to affect the foundation. It turns out that thermal insulation from the inside only saves to some extent from heat loss, but does not protect the base in any way.

Besides, with internal insulation, the useful area of ​​the room decreases, which can be important in the case of operated basements. Finally, with internal thermal insulation, the vapor permeability of surfaces is almost always violated, as a result of which the room is filled with moist vapors, its microclimate is disturbed.

If moisture vapors do not have time to be removed, they risk settling on the surfaces of the foundation, insulation, and finishing material. All this leads to their getting wet and loss of performance properties. Wooden surfaces begin to rot, corrosion appears on metal, erosion appears on concrete, insulation loses its thermal efficiency.

It is possible to prevent such phenomena by organizing a vapor barrier layer, as well as accurately calculating the thickness of the insulation. It is important that the dew point (the boundary where moisture vapor turns into droplets) falls on the outer layer of the insulation or beyond.

Particular attention should be paid to the joints of the vertical surfaces of the foundation and the floor, floors, joints of surfaces, since with internal insulation, it is in these places that there is a high probability of the appearance of "cold bridges".

It should be noted that external thermal insulation is more effective and therefore preferable. Experts recommend using the internal one only if it is impossible to implement other methods.

Another important question that worries homeowners is when to insulate the foundation. Ideally, this is done at the stage of its construction, after removing the formwork or installing the grillage on the pile foundation. In this case, it is possible to achieve the most hermetic insulation, to produce a better external insulation, and also to reduce the labor intensity of the process.

An important point in external insulation is the thermal insulation of both the vertical surfaces of the foundation and the horizontal blind area. It is with insulation during the construction phase that this recommendation can be implemented.

However, if this did not work out, insulation can be done in an already built house.

As already mentioned, any building can be insulated. The choice of a specific method depends on what kind of device the foundation and the structure itself have, how high the heat loss of the object is.

In general, internal insulation is carried out according to the same principles as external insulation. To do this, you can use polystyrene foam plates (not recommended for operated premises due to their environmental insecurity), polyurethane foam spraying or foam foam.

These heaters are attached to the waterproofing layer, after which the cladding is performed (by contact method or according to the principle of a ventilated facade).

There is also a technology for thermal insulation with expanded clay, but the layer thickness in this case should be at least 0.3 m.A wooden formwork with a height from floor to ceiling is created, which is waterproofed from the inside and covered with expanded clay.

It involves the release of the foundation from the soil, the restoration of its contours, and the cleaning of surfaces. The most important step is waterproofing. Insulation is carried out only on top of it. The materials and technologies used will be discussed below.

As mentioned, this is the preferred option. It can be done in 2 ways:

• be a non-removable insulated formwork;
• imply the thermal insulation of the base immediately after it has been stripped.

In the first case, it is supposed to create a formwork, the inner and outer walls of which are made of polystyrene foam plates of suitable strength. A concrete mixture is poured into the formwork in compliance with the technological requirements provided for the strip foundation, after which it is left for a month to gain strength.

There is also a second method of insulation during the construction phase - for this, formwork is also being prepared, which is poured with concrete. After the specified period of time, the formwork is removed (usually it is a wooden structure), the surfaces of the foundation, if necessary, are leveled, covered with a primer. Next, the base is waterproofed with bitumen-based roll materials. The next step is to insulate the foundation, after which it is closed with protective and decorative materials (contact materials - paint, plaster, as well as hinged basement siding, panels, clapboard, etc.).

In general, the insulation of the foundation of a residential building is similar to the insulation of a newly built base, but it involves a greater amount of earthwork, which will have to be done manually. The process involves dismantling the blind area and decorative trim of the basement. The next step is to dig a trench to the depth of the foundation. After that, you should prepare the foundation for insulation, if necessary, carry out or update the waterproofing and proceed with the installation of the insulation. The work ends with backfilling of the foundation, installation of facade materials and blind area.

Old wooden houses often lack foundations. They were erected immediately on the ground and placed on several stones for reliability. However, over time, the lower part of the log house rots and sags. The situation can be corrected by raising the log house with special jacks, restoring its geometry by replacing damaged wooden elements, which are pre-treated with antiseptic compounds. Then the house is put in place.

The use of polyurethane foam for insulating such buildings raises doubts from the point of view of the thermal efficiency of such a technology. At the same time, it is safe to say that the wood under such a layer begins to rot much more actively.

If we are talking about old, undefended houses with a foundation, then the difficulty in warming may be associated with a strong uneven foundation. This is due to the lack of formwork during pouring. In this case, they resort to insulation with expanded clay.

A trench is also being dug to the depth of the foundation, which is waterproofed and covered with expanded clay.

The most widespread for insulation of both vertical surfaces and blind areas, and also as a heater under the foundation slab received expanded polystyrene. It has 2 varieties - well-known foam and its extruded modification.

According to their thermal insulation characteristics, all materials based on expanded polystyrene demonstrate a low coefficient of thermal conductivity.

It is very convenient to use expanded polystyrene, since it is produced in plates with a smooth surface. Fixation is provided by means of glue or bitumen mastic. It is important that the composition is free of solvents.

It is important to remember when working and storing the plates that they cannot be exposed to UV rays. Otherwise, the material is destroyed. In this regard, immediately after the installation of expanded polystyrene insulation, they should be covered with a decorative layer or sprinkled with earth. If this is not possible, temporary protection must be provided with a covering material. The boards should be stored packed.

A more modern insulation is polyurethane foam, which also has a low coefficient of thermal conductivity, moisture resistance, strength, environmental friendliness and incombustibility. It is applied by spraying on a surface with a thickness of 3-10 cm. Due to the peculiarities of application, it is possible to achieve the solidity of the layer - it penetrates into the smallest cracks, lays down without joints between the elements. This is a guarantee that there are no “cold bridges”. As a rule, professionals with the necessary equipment are invited to perform the work.

Like expanded polystyrene products, polyurethane foam is destroyed by ultraviolet radiation. Another feature is the impossibility of a contact coating of the insulated surface, therefore, before spraying, a crate should be mounted, on which the facade (basement) materials will be mounted in the future.

Penofol insulation is also a relatively new technology, involving the use of roll material based on polyethylene foam. It has good thermal insulation properties and, moreover, has the ability to reflect heat.

Thanks to this, penofol acts on the principle of a thermos - it does not release heat from the room during the cold season and prevents it from heating up in the summer heat. In addition, the presence of a foil coating increases the strength of the material, allowing it to keep its small thickness, and provides additional waterproofing of surfaces.

Expanded clay of medium and fine fraction is usually used as bulk insulation. This natural clay-based insulation demonstrates high heat and vapor barrier performance, is nonflammable, environmentally friendly and affordable. However, it quickly absorbs moisture, so when using expanded clay, you should take care of additional waterproofing of the insulation layer.

Mineral wool, which has high thermal insulation characteristics, is rarely used due to its low moisture resistance and low rigidity of the material. The only exceptions are mats made of high strength basalt fiber. However, they are also used to a greater extent as internal insulation for operated basements.

The main requirement for basement heaters is a low thermal conductivity coefficient. It is important that the material has high moisture resistance. That is why such popular mineral wool (which is not inferior to expanded polystyrene in its thermal insulation properties) is rarely used for foundation insulation. She quickly gets wet and loses her qualities.

Only sometimes mineral wool is used as an internal insulation of operating foundations. However, in this case, it is necessary to use more expensive basalt fiber, as well as diffuse membranes for vapor and waterproofing. Such a layer is not cheap at all.

Another important requirement for insulation is high strength., since the material has to withstand increased mechanical loads (static and dynamic), resist soil deformations.

The parameters of environmental and fire safety for foundation materials that are important when using wall heaters are fading into the background.

Let us consider in more detail the most important characteristics of the above insulation materials for the foundation. The maximum thermal efficiency is possessed by expanded polystyrene plates, the heat loss coefficient of which is 0.037 W / m2K. For a clearer idea of ​​how good it is, we give the indicators of heat loss of air (the best heat insulator) - 0.027 W / m2K, wood - 0.12 W / m2K and brick - 0.7 W / m2K. Now it is clear that polystyrene foam surpasses almost all other materials in its thermal efficiency.

The heat loss coefficient of expanded clay is 0.14 W / m2K, polyurethane foam (depending on the type of working base and thickness) - in the range of 0.019-0.03 W / m2K. The thermal conductivity of penofol is 0.04 W / m2K, while it is capable of reflecting up to 94-97% of thermal energy.

Plates based on extruded polystyrene foam do not absorb moisture, as well as polyurethane foam.

Polystyrene foam insulation has a flammability class G1-G4 (depending on the type, that is, it is combustible, releases toxins when the temperature rises), expanded clay and polyurethane foam have a flammability class NG (non-combustible), the latter, depending on the type, can also be classified as G1, G2.

High-quality insulation can be obtained only if the entire horizontal surface of the foundation and the vertical node of the blind area are covered with heat-insulating material.

Regardless of whether the basement of a building object or the basement of an operated house is being insulated, do-it-yourself insulation should begin with the preparation of the foundation. To do this, it is cleaned from the ground over the entire surface, starting from the wall and ending with the base. As a result, a trench is formed along the entire perimeter of the foundation. It must be wide enough for workers to carry out their functions.

In a building under construction, a trench can be dug with an excavator, in a finished house you will have to work manually with shovels.

The vertical surface should be cleaned of soil and other contaminants, and dried. If dents and cracks are found, seal the concrete bases with a special quick-action polymer. Unlike cement mortars, they solidify after 12-24 hours.

If there are roughnesses and protrusions, it is better to beat them off, and then walk along the surface with a grinder with a nozzle on a stone or wood.

The actions considered are common for most types of foundations (including foundations on screw piles with a strip element).

The next stages of work vary depending on the type of foundation. Consider the features of the technology, characteristic of a particular base design.

The prepared concrete surface is coated with a primer, which will improve adhesion and act as a kind of insulation for waterproofing. It is important to evenly coat the foundation with a primer and wait until it dries completely.

The next step is gluing or fusing waterproofing. It is attached from top to bottom and also implies a final monolithic coating without gaps.

After organizing a layer of waterproofing, they begin to warm. For this, polystyrene foam plates are often used, on which an adhesive is applied.It is more convenient to do this with a notched trowel, calculating the amount of glue in such a way that its excess does not protrude beyond the plate when fixing. If this happens, wipe off any excess glue immediately.

If it is necessary to apply insulation in 2 rows, the second row is glued with a slight offset relative to the first. Row gaps must not overlap. When an inter-seam space appears, it is filled with construction foam, the excess of which, after hardening, is cut off with a knife.

To fix the expanded polystyrene boards located below the ground level, it is enough to use glue, since after filling the ground, the slabs will be reliably pressed to the surfaces.

That part of the insulation that falls on the base is additionally fixed with disc dowels. In this case, a hole of the required diameter is pre-drilled in the surface of the plates, after which the fastening element is inserted into it.

Thermal insulation is completed by backfilling the foundation and tamping the earth around, protecting the insulation with a decorative layer, if necessary with a hydro-windproof film.

Thermal insulation of the pile foundation involves digging a trench between piles 50 cm deep. The third part of it is covered with sand, after which a frame made of reinforcement is poured with concrete. After the time required for its setting, the space between the floor and the ground is laid with bricks along the entire perimeter, while maintaining small ventilation gaps.

After that, the masonry is covered with a layer of insulation (mainly EPP), reinforced with mesh and plastered.

The columnar foundation is insulated in the same way as the pile foundation. Instead of brickwork, in both cases, metal profiles or wooden blocks can be used. The former should be protected with anticorrosive compounds before use, the latter with antiseptics and antipyrine.

If necessary (harsh climatic conditions), perlite is added to the concrete solution or it is laid as a pillow interspersed with sand.

The slab foundation is insulated from the side that in the future will face the interior of the house. For this the foundation slab is covered with a layer of waterproofing, and then a layer of insulation is laid (usually sheets of expanded polystyrene of increased strength or penofol). A layer of heat-insulating material is covered with a polyethylene film laid with an overlap of 10-15 cm and fixed with double-sided tape.

If in the future it is planned to fill the load-bearing floor, then it is carried out directly on a heat insulator protected by a film and knitted reinforcement laid on it to enhance the bearing capacity of the floor. If it is supposed to use welded reinforcement, then first a floor screed (concrete or cement-sand) is made over the insulation and protective film, and then welding is carried out.

Not every homeowner can properly insulate the foundation. Experienced craftsmen distinguish the following among the most common mistakes:

• No or insignificant thermal insulation effect. The reason for this phenomenon is the insufficient thickness of the insulation, its getting wet or the preservation of "cold bridges". In any case, this is a serious mistake, the correction of which is possible only by dismantling the structure and redoing the work. An accurate calculation of the thickness of the insulation, high-quality waterproofing, adherence to technological standards during installation allows you to avoid trouble.

• Freezing of the corners of the basement. It is connected with the insufficient thickness of the insulation layer on the horizontal surfaces of the blind area in these areas (it is the corners and the adjacent surfaces that are the most vulnerable).Avoiding such an error will again allow an accurate calculation of the thickness of the insulation, as well as additional thermal insulation in the corners of the object (the insulation is usually laid in 2 layers);
• High humidity in a technical basement or an exploited basement. This happens when trying to organize a warm base by means of internal insulation.

If such a nuisance happened during external insulation, it means that the technology of laying the facade material is violated (a gap must remain between it and the insulation), there are no or insufficient technical holes, or they are in "dead zones" (for example, covered with snow). You can avoid the problem at the planning stage (by making the correct calculations in accordance with SNiP) or by installing forced ventilation.

For information on how to insulate the foundation with your own hands, see the next video.