Thermal insulation of the foundation structure allows us to simultaneously solve two important problems: to reduce the heat loss of the heated rooms through the basement, soil or subfloor, as well as to save the material of building structures from destruction during winter freezing of the soil.
Arguing whether it is necessary to insulate the foundation of the house from the outside, it should be understood that both concrete and other materials from which the foundations are built are only conditionally considered waterproof. A small top layer of concrete is able to absorb moisture, which will freeze at low temperatures, expand and lead to a violation of the integrity of the foundation.
As a result of repeated freezing of the soil and insufficiently strengthened hydraulic insulation, the building structure can be severely damaged or even destroyed.
Heat loss through the floors and the basement of the building can reach 15% of the total. This is especially noticeable on slab bases and in the construction of houses without basements. Therefore, the insulation of the foundation of the house from the outside will make it possible to save significant funds on energy resources, the cost of which is constantly growing.
General requirements for insulation
The foundations of buildings are regularly exposed to moisture, temperature changes with possible freezing, they are subject to constant ground pressure, both in the transverse and in the longitudinal direction. How to insulate the foundation of the house outside? First of all, the selected insulation must have:
- low thermal conductivity;
- resistance to temperature extremes in the range from -40 ° C to + 20 ° C;
- resistant to moisture, impervious to it;
- good strength while maintaining the structure under pressure on the surface;
- unattractive to mice and insects.
The combustibility of the material for external insulation of the foundation, located below ground level, does not matter, since the probability of exposure to the flame is extremely low. There are also no special conditions for vapor permeability, although water resistance already implies the presence of this parameter.
Types of insulation used
Among the insulation materials that meet the above requirements and have an affordable cost, we can name:
- sprayed polyurethane foam;
- polystyrene sheet;
- extruded polystyrene foam;
- expanded clay.
Each of the listed types of thermal insulation has its own characteristics associated with the installation technology, the effectiveness of the insulation layer and the magnitude of the cost of acquiring the material.
Polyurethane foam (PPU)
Of all the listed heaters, sprayed polyurethane foam is the most expensive and requires the use of special equipment for applying it to the surface of the material. However, this is the most effective insulation of all existing polymeric materials.
Its main feature is that the PPU coating does not have connecting seams, representing a single continuous layer. This material for warming the foundation of the house outside:
- possesses excellent adhesion and keeps well even on contaminated surfaces;
- has one of the lowest thermal conductivity;
- after full hardening becomes waterproof;
- characterized by good hardness combined with high ductility;
- completely unattractive to rodents and insects.
The water resistance of polyurethane foam allows you to abandon the device of the waterproofing layer. This significantly reduces the time required to insulate the foundation of the house from the outside, reduces the overall cost.
Conventional polystyrene boards
This material is made by heating the feedstock poured into the mold with hot steam. Under the influence of temperature, polystyrene granules expand, forming a porous mass, which occupies the entire volume of the form. This technology is used to make most soft foams.
PPS is supplied to the market in the form of flat plates with a lock recess at all ends. This form allows partial overlap of the joints at the junctions of adjacent plates and to avoid the formation of cold bridges.
The material is cheaper than PPU, but the presence of connecting joints cannot guarantee the protection of the surface from moisture. Therefore, before installing the thermal insulation layer, a mandatory waterproofing device is required.
Extruded Styrofoam
This material differs from the previous version by the manufacturing technology and the quality of the plates. The molding of the plates provides for the supply of the finished molten polymer mixture through a special extrusion machine. In this case, the foaming of the composition occurs due to its filling with neutral or carbon dioxide. Normal air is not used for this, as this will affect the fire hazard.
Extruded polystyrene is somewhat more expensive than usual, but thanks to this molding method, it does not have a single open pore on a smooth and even surface. This means a longer service life and improved thermal insulation properties.
Expanded clay
The main advantage of expanded clay granules is the lowest cost among all heaters used for foundations. For other technical indicators expanded clay, frankly, loses to foamed polymers. The use of new modern technologies for warming building structures has made this material weakly in demand; its use is now rare.
The ability of expanded clay to partial water absorption over time increases its thermal conductivity by 25-30%. Therefore, ensuring the effectiveness of the bulk thermal insulation layer requires a large thickness, and, therefore, a significant consumption of material. This, in turn, leads to an increase in costs and, as a consequence, the complete leveling of the main advantage of expanded clay mentioned above.
Features of the application of thermal insulation for foundations
Warming is performed only for two types of foundation foundations - tape and slab. Speaking of thermal insulation of pile and columnar structures, they mean the installation of insulation on the bottom surface of the plate, which is the floor of the first floor, and the insulation of the basement base from the outside.
Insulating support pillars and piles simply does not make sense. In these places, there is practically no temperature difference between the surface of the building structure and the environment.
Polyurethane foam application
For the professional performance of thermal insulation work, a two-component composition of PPU and special equipment for mixing and spraying the finished mixture are used.
Before starting work, the surface must be cleaned of old plaster layers and large contaminants. It should not have grease stains and loose layers of building materials. Thorough cleaning and priming are not required if the surface is dense and durable.
Styrofoam plates
Speaking about the installation of expanded polystyrene plates, first of all it is necessary to study:
- the need for a waterproofing layer;
- the method of mounting plates on the vertical surface of the foundation;
- protection of the polymer from negative environmental influences.
As hydraulic insulation, roll materials with bitumen impregnation are used. They glue the surface with hot bitumen.
The use of primers or other liquid materials is not recommended, as they will not be able to ensure the possibility of normal fixing of the insulating material on the surface.
Initially, PPS boards are fixed to the surface using special glue. When installing adjacent elements, it is necessary to provide locking joints for sealing joints. The final fixing of the plates is carried out using special plastic nails with large round caps (fungi).
Slabs from ordinary PPP, which is made thermally, are subject to protection from negative influences. This is due to the presence of open pores on the surface of the material. Processing can be done with cement or stable adhesive mortar, which is applied after installation of the plates.
Expanded clay filling
The foundation wall should be covered with a waterproofing layer of rolled materials. To warm the strip foundation with expanded clay, they dig a trench 40-60 cm wide along the perimeter of the building to the depth of freezing of the soil.
A sand cushion 5-7 cm thick is poured at its bottom. After that, the trench is completely covered with expanded clay granules to the level of the blind area, well tamped. The blind area is poured directly onto the expanded clay layer.
For slab foundations, an expanded clay layer can be used as a support pad instead of sand. Granules are poured with an even layer with a thickness of 70-100 mm, plates of the main heat insulator are laid on them, onto which concrete is then poured.
DIY insulation instructions for the foundation outside
The technology of installing thermal insulation on the foundation depends on the type of construction of the base and the time of year of the work.
To warm the underground part of the strip foundation, it is necessary to provide free access to the surface of the building structure. For a building under construction, this is easier to do. The insulation is mounted immediately after removal of the formwork before performing backfill.
For already operating buildings, it is necessary to dig a trench at least 500 mm wide along the perimeter of the house, to the point of freezing of the soil.
The tile base is insulated with heat-insulating plates only during the installation of the structure.
Strip foundation
The most common option for warming the vertical walls of the foundation tape from the outside is the use of extruded polystyrene boards.
The installation procedure in this case is as follows:
- Dig a trench along the perimeter of the building with a width of at least 0.5 meters and a depth to the bottom of the base or the freezing point of the soil;
- thoroughly clean the wall surface from soil residues and other contaminants, give time to dry well;
- apply 2 times a layer of bitumen soil, which can be bought ready-made or made from a primer;
- using hot bitumen, glue two layers of rolled hydroisol, ruberoid or other similar material onto the foundation wall;
- start installation of expanded polystyrene plates with laying the bottom row, providing primary fixation using special mounting glue;
- final fasten using plastic mounting nails with a wide hat using at least 5 pcs. on one plate.
When laying the plates, it is necessary to observe the engaging locking connection of the neighboring insulation elements. Vertical seams of the second row should not coincide with the seams of the first.
After the installation of expanded polystyrene plates is completed, it is necessary to backfill the trench with layer-by-layer ramming. The blind area can only be completed after a year, when the final shrinkage of the soil occurs.
Slab foundation
Warming of the foundation slab is carried out at the initial stages of the construction of the house and is included in the overall scope of work on the construction of the foundation foundation.
Therefore, the instruction includes part of the construction work of this stage:
- remove the topsoil layer to the design depth;
- level and tamp the surface;
- spread a layer of geotextile, which is designed to prevent the capillary rise of groundwater and the germination of weeds;
- pour a layer of crushed-sand or expanded clay cushion 100 mm thick, tamp it well;
- lay a layer of plastic film with overlapping adjacent strips by 100-150 mm;
- lay polystyrene plates on the surface with the provision of locking joints and offset joints along horizontal rows;
- for reliable fixation of adjacent elements of the insulating layer, connect them together using metal or plastic staples;
- cover the plates with plastic wrap and fix it on the surface.
After this, you can proceed with the installation of the formwork and the collection of the reinforcing frame for pouring concrete.