Insulation of the strip foundation: answers to popular questions

The heated debate about whether to insulate the foundation or not gradually subsided - experience has shown that this event is about 20% reduces heat loss at home, prolongs its life and keeps the heated basement or basement dry floor. Like the foundation of any other type, it is better to insulate the tape during its construction - we will consider how to do this further.

What is the point in insulating a strip foundation?

In winter, the soil freezes, increases in volume and can push out even a heavy foundation (in central Russia by 200 mm), and in spring the foundation sinks. The result of such movements are cracks and deformations of the foundation, skewed walls, window and doorways. Thermal insulation materials reduce the influence of the surrounding cold soil layers on the areas under the house, the risk of frost heaving loads is greatly reduced. Clause 12.2.5 of SP 50-101-2004 allows you to assign the depth of the external foundations regardless of the calculated the depth of freezing, if "special heat engineering measures are provided to exclude freezing soils ".

instagram viewer

When is tape insulation required?

The strip foundation is necessarily insulated in the following cases:

If a warm basement is made in the house.
If the foundation is laid above the freezing depth.
The foundation is insulated if the soil on the site is prone to heaving.

How to insulate the strip foundation?

The materials for the insulation of the strip foundation are polystyrene and expanded polystyrene. These are plates, so they are convenient to install, they are quite durable and are not afraid of moisture. If the insulation is mounted both horizontally and vertically, then the vertical sheets are installed first. The corners of the foundation are insulated with a 1.5 times thicker layer of material, because there is always more heat loss in the corners. The shallow strip foundation can also be insulated with fixed formwork. Expanded clay is often used for insulation (but you need to keep in mind that it absorbs moisture and has high thermal conductivity).

Is the foundation insulated from the outside or from the inside?

It is the external insulation that will maximally protect the foundation from the cold. When insulated from the inside, the structure remains open to the effects of soil heaving, low temperatures and moisture.

Often, the foundation is insulated already during the operation of the house, as they say, on FORUMHOUSE, "When the foundation starts to crack." It is wrong, it is more effective to insulate the base during its construction.

What should be the thickness of the strip foundation insulation?

In practice, in regions with cold winters (below -20 degrees), strip foundations are insulated with 50-70 thick foam plates mm, if the winters are not easy cold, but frosty, and the temperature drops below -30 degrees, the thickness of the slab should be 100 mm. In the north of our country, plates with a thickness of 150 mm are used for insulation. Expanded polystyrene is superior to polystyrene in a number of indicators and its layer for insulation of the tape may be less, but here everything is individual.

How is the insulation of the strip foundation carried out?

A good way to obtain an insulated foundation is a permanent formwork, which insulates the foundation both from the outside and from the inside.

Expanded polystyrene is usually used to insulate the foundation of an already built house, although these materials are also used during construction. The insulation is mounted on smooth, concrete-free foundation walls on polymer-cement mixtures. When insulating the basement part, the insulation is additionally attached with dowels.

In the case of MZLF, not only the walls of the foundation are insulated, but also its base; slab insulation is laid both vertically and horizontally. Whatever sheet insulation is used, its joints must be sealed with glue or mastic. If you need two layers of insulation, it is mounted in a checkerboard pattern so that the joints of the rows are in different places.

Since the insulation is placed on a sand cushion, the trench is made deeper, and the thickness of the formwork should not be less than the thickness of the insulation.

Do I need to insulate the blind area?

Insulation of the blind area allows you to reduce the depth of freezing, to the point that the soil will not freeze at all. As a result, two birds with one stone are killed: both the heat loss of the house and the effect of the forces of frost heaving on the foundation are reduced.

The blind area is not always insulated, it depends on the type of foundation, the type of soil and the presence of a base, but there are two axioms:

the blind area and the basement are insulated if the house is on heaving ground;
there is no point in insulating the blind area if the foundation is not insulated.

An uninsulated foundation will become a wide gap for cold penetration between the warm blind area and warm walls: money and labor will be wasted.

The blind area is insulated if the house has a shallow foundation - in this case, its width should exceed the depth of soil freezing. With buried foundations, the blind area is insulated when a warm basement floor is planned in the building. The meaning of insulation is to reduce heat loss and reduce heating costs, and if there is no heating in the basement, the insulation of the blind area will be excessive.

How did you insulate the foundation? Write in the comments!

Like it, share the publication!

Friends, there are already 30 thousand of us! Subscribe to our channel -we are working,so that you receive only useful and relevant information!