Strip foundation is one of the most common structural solutions for building a foundation for a private house. It has sufficient strength potential, but the walls and bottom require good insulation. It is especially important to implement high-quality insulation of the strip foundation, not only in the outer part, but also inside the structure.
Choosing a heat insulator
Usually use expanded polystyrene grade FS 20. It is advisable to install panels with profiled edges, which will prevent the formation of cold bridges at the joints. You should also take into account the inadmissibility of a combination of expanded polystyrene and solvents that may be present in liquid waterproofing compositions - mastics, tar and xylamite dissolve such materials. For this reason, it is worth using insulation of the strip foundation with Penoplex, which in itself can act as a waterproofing coating. Special models of slabs are selected that are suitable for protecting the structure from groundwater.
No less popular heat insulators in the form of mineral and glass wool are used only if their density is at least 110 kg/m3. Other designs let water through, which is also undesirable for insulation under the foundation.
Another option is expanded clay. This is a loose insulation resistant to frost, moisture, fire and biological processes of destruction. But due to structural expediency, it is recommended to fill it up before the foundation is laid on the bottom of the pit.
What tool do you need?
A specific set of tools is determined by the material and technique of insulation. As a rule, the following devices are involved:
- Shovel (bayonet and scoop).
- Installation tool for working with concrete, metal and wood (formwork). It can be a hammer drill, electric drill, hammer, jigsaw, etc.
- Tools for the preparation and application of insulators are spatulas, rollers, a rule and a foam gun.
- If you plan to insulate the strip foundation with liquid bituminous waterproofing, then you will need a gas burner.
Among auxiliary materials and consumables, geotextile fabric, fasteners, adhesives and tapes, adhesive tape, primer and sealer may also be required.
General recommendations for thermal insulation
Initially, you should keep in mind the following tips from specialists involved in the construction of strip foundations:
- Select the methods and tactics of isolation should be based on the results of engineering and geological research on the ground. At a minimum, such a report would identify groundwater protection requirements that negatively affect almost all thermal insulators.
- Particular attention during installation is given to joints and gaps. It is they who form cold bridges, which become the main cause of heat loss.
- It is important to have a balanced approach in both insulator selection and installation. For example, insulation of a strip foundation with polystyrene foam should be made with a thickness of about 3-5 cm and no less. There is no point in increasing the insulation parameters either, since this deviation from the technology will affect the structural reliability of the insulation.
- Saving on fasteners is a common mistake of novice builders. Experts note that it is impossible to shift the necessary fixing force of the heat insulator to subsequent structural layers. Each element must receive sufficient fastening precisely in its structure at a specific level.
Preparing the job site
Installation of heat-insulating plates is carried out only on a flat base. The structure of the strip foundation from different sides must be cleaned, and, if necessary, primed in places with defects. It is important to eliminate efflorescence on the surfaces, as they will not allow sufficient adhesion. Liquid and roll insulation of tapefoundation with a waterproofing barrier is carried out only on surfaces primed with a bituminous mixture. Also, by the time of installation operations, the heat-insulating material should also be prepared - it must first lie in a dry room, not have defects and other signs of damage in violation of integrity. If necessary, the plates can be cut to the desired size with a regular hacksaw or jigsaw.
Waterproofer device
Protection against water and moisture in relation to foundations is almost always used. Exceptions include only cases when rubble stone or waterproof concrete is used in the structure itself, but this is not common in strip foundations. To protect against groundwater with soil moisture, vertical and horizontal hydrobarriers should be used. The function of vertical waterproofing is to a lesser extent manifested in the insulation system of a shallow strip foundation, since groundwater is almost not afraid of it. It is enough to perform film or bitumen protection of wall surfaces with a small entrance under the ground up to 30-50 cm. This barrier will retain mainly atmospheric and groundwater. As for the horizontal waterproofing, it is laid in two places - at the junction of the foundation walls and the outer walls, as well as in front of the structural support cushion across. This layer should cut off water, which will reach the structure of the walls and, as a result of capillary suction, contribute to their destruction.
Technology for performing extern althermal insulation
Thermal insulation in the construction of the strip foundation should be laid to a depth of about 50 cm. The installation of extruded polystyrene foam, in particular, is carried out after waterproofing. If polyurethane foam is used, then it should also be covered with film waterproofing from the outside. The thickness of the mounted plates should be 3-4 cm for expanded polystyrene, and 5 cm for expanded polystyrene. Mineral wool is laid in a layer of 6 cm. According to the technology of warming the strip foundation from the outside, fastening should be carried out with acrylic glue (pointwise) and dowels about 12 cm long. Additionally, you can also lay a plastic reinforcing mesh, fixing it on the sides at the joints to the wall.
Performing internal thermal insulation
Many experts are skeptical about the device of internal thermal insulation for the foundation, relying on the full insulation of the walls of the house along the entire height. This is due to the fact that from the inside the same polystyrene foam will not exclude cold bridges if they have not been eliminated from the outside. However, it is in this part that mineral wool can appear well. Mats with a thickness of 10 cm are used, which are mounted in the construction of the crate and covered with film waterproofing. It is also mandatory to insulate the floor of the strip foundation, in which it is worth using bulk materials. In addition to expanded clay, sawdust and other environmentally friendly waste from natural industries are used in this part. Above the first layer of the log, an underground niche is arranged on the grillage. Its thicknesscan be 10-15 cm, which will be enough for filling loose insulators, and for laying tile materials even without fixing.
Protection of insulation layers
From the outside, the layers of arranged insulators must be protected from mechanical damage. For example, during the backfilling of the foundation, pebbles and various debris contained in the soil may well deform the insulating plates or break the seal in certain areas. Therefore, to protect the insulation layers of the strip foundation from the outside, it is necessary to use thin and durable polymer sheets or foil film. This material is attached to a moisture-resistant adhesive base or to silicone sealant, but without the use of hardware.
Conclusion
Insulation of the foundation is the basis for the conservation of thermal energy at home. Approach to solving this problem should be comprehensive, taking into account the operating conditions of the material and the factors of external influence. So, when insulating a strip foundation, both the requirements for insulation from groundwater and the structural characteristics of the walls are taken into account. When choosing a material, such qualities as wear resistance, vapor impermeability, rigidity and compatibility with adjacent surfaces, primarily with concrete, must be calculated. Do not forget about internal insulation, since cold bridges with condensate also negatively affect the condition of concrete surfaces from the back. Properly organized complex thermal insulation will provide a comfortable microclimate in the house for many years.
