Insulating the foundation from the inside for a house using this is not the most reasonable idea, but it is quite doable. The fact is that insulating the foundation from the inside for a house has many problems that will certainly come to light after such insulation is carried out.
However, in cases where there is simply no other choice, this method can be implemented, including with your own hands.
The first step is to figure out how to insulate the foundation for a wooden house, or any other, inside, and then smoothly move on to why this idea is obviously a losing proposition and why there will be more problems at the end than advantages.
1 The process of insulating the foundation from the inside
First of all, it should be remembered that insulating the foundation of a wooden house inside is acceptable only for a buried type of foundation, when its underground part is, strictly speaking, the basement of the house.
In other cases, for example, for a strip foundation, insulation with expanded clay, foam plastic, or anything else cannot be done with your own hands due to the lack of meaning in this action.
If this procedure is needed not for a strip foundation, but for a buried foundation, then before performing it you should select a material for insulation.
An important parameter and property of thermal insulation materials that should be looked at is the thermal conductivity coefficient. In addition, you should also look at the characteristics of the thermal insulation material in order to find out under what operating conditions it can be used.
The most preferable option for insulating the foundation for a wooden building from the inside is foam insulation. Do-it-yourself foam insulation in this case is good because it has fairly high thermal insulation qualities. This material is also applicable for strip foundations, although this plus is not relevant to this situation.
2 Reasons not to insulate the foundation from the inside
There are five good reasons why carrying out such construction work is inappropriate. They are presented like this:
- Freezing of the entire reinforced concrete structure of the building even with. In such a situation, the foundation is not protected in any way from unstable temperature fluctuations, which has a detrimental effect on its service life;
- Due to the fact that there will be a shift in the so-called “dew point” to the “insulation-foundation” boundary, it will subsequently be necessary to add an additional vapor-proof layer, which will impact the overall budget of insulation work;
- The implementation of the previous point will lead to disruption of the microclimate in the basement, and the air humidity will increase quite significantly. Consequently, it will additionally be necessary to install effective ventilation, which will once again negatively affect the overall budget;
- Due to such a huge amount of additional equipment, the space inside the basement will be significantly smaller than the original;
- In general, the end result is that the building owner will have huge financial costs for the construction work itself and the purchase of various materials, which the method of external thermal insulation does not have.
Insulation of the foundation from the inside is carried out at the stage of building a house. It happens that you have to do this after several years of operation of the building. Improperly performed thermal insulation of the internal walls of the foundation in a wooden house or its complete absence can contribute to the destruction of the foundation structures of the building. To avoid this, you need to insulate the foundation from the inside and outside. This article focuses on how to insulate the foundation from the inside of a house.
Why is it necessary to insulate the foundation from the inside?
If the project included errors in the thermophysical calculations of the house’s foundation structures or the builders made defects in their work, then this will certainly affect the condition of the supporting structures. At low external temperatures, basement walls that are not protected by thermal insulation will freeze.
As a result, condensation will accumulate on the internal surfaces of the foundation. High humidity will contribute to the appearance of mold, large fungal formations, various insects and harmful microorganisms. This entire biological microsystem will begin to actively destroy the structures surrounding it.
If measures are not taken in a timely manner to insulate the foundation from inside the house, this can result in considerable financial costs for repairing the basement.
Construction of a basement is possible only with the construction of a strip foundation. The basement walls are the internal surfaces of the foundation. It makes no sense to insulate supporting structures underground. The internal walls of the above-ground part of the foundation and basement are covered with thermal insulation.
How can you insulate the foundation from the inside of a house?
When it finally becomes clear that it is necessary to insulate the internal walls of the basement, you need to decide how to insulate the foundation. The choice of thermal insulation material is influenced by factors such as quality characteristics, ease of use, environmental friendliness and cost.
A wide range of thermal insulation materials on the building materials market allows you to choose the right thermal insulation. Mainly:
- mineral wool;
- Styrofoam;
- expanded polystyrene;
- polyurethane foam.
All these materials are produced in the form of slabs. Polyurethane foam is an exception in this regard. The polymer is applied to the walls in the form of foam.
Mineral wool
The material is a foamed fibrous mineral mass. Cotton wool comes on sale in the form of rolls or mats. Mineral wool with a thickness of 50 mm or more provides reliable thermal insulation of basement walls. The material is easy to cut.
Thanks to special additives, modern wool is hydrophobic, unlike mineral wool produced in the last century. Therefore, I use it without fear for insulating underground rooms.
Mineral wool is cut into separate mats, which are attached to the walls around the perimeter of the basement or plinth. Mineral wool cladding must be covered with a final finish (putty, plaster).
Styrofoam
The fine-cell polymer is lightweight and has high thermal insulation. Polystyrene foam is easy to process and has such qualities as hydrophobicity and immunity to organic formations on its surface. The cladding of the internal walls of the foundation is made of foam plastic slabs with a thickness of 40 mm to 120 mm.
The slabs are fastened with hot bitumen mastic. If the base of vertical fences is monolithic, the foam is secured with dowels - fungi. The dowel has a wide polymer cap and does not dent the soft structure of the material.
Also, foam plastic is installed on the foundation wall using a special cement adhesive composition. Apply glue to the back of the slab with a trowel in the corners and in the center. The foam sheet is then pressed against a vertical surface.
Fine-cell thermal insulation is a fragile material, so the foam lining must be covered with a finishing finish.
In central Russia, it is enough to insulate the foundation of a wooden house with slabs 40–50 mm thick. Some owners of wooden houses successfully use foam packaging for large-sized goods for various purposes (furniture, household appliances, etc.) as thermal insulation.
Such use of the material will not only not deteriorate the quality of thermal insulation, but will also bring certain savings in money. To prevent cold bridges from arising, the seams between the slabs are carefully sealed with sealant.
Expanded polystyrene
Expanded polystyrene is the same foam plastic that has been subjected to pressure treatment at high temperatures (extrusion). Extruded polystyrene foam boards are also known as penoplex.
Penoplex is produced mainly in three types: for insulating walls of premises (PS), foundations (PF) and for roofing (PC).
Table of standard sizes of penoplex slabs
Penoplex is attached to walls covered with waterproofing (bitumen mastic, geomembrane, roofing felt or roofing felt). Dowels and nails with an extended head (fungus) are used as fasteners.
Some “experts” claim that dowels of this type create cold bridges. However, in reality this is not the case. The “metal nail” is located inside a polyethylene dowel, which itself is a good heat insulator. Therefore, there is no need to be afraid to install an extra dowel - fungus.
The sides of the penoplex slabs are made in the form of a locking system - “groove - protrusion”. By inserting the protrusion of one slab into the groove of another slab, an almost seamless coating is obtained. Unnoticeable seams must be puttied.
To reliably fix the finishing coating (putty, plaster), a fine-mesh polymer mesh is glued onto the penoplex. If ceramic cladding is intended, a metal mesh is attached to the polystyrene foam. For fastening, a special adhesive for polystyrene foam is used.
Polyurethane foam
Coating with polyurethane foam is carried out using a special installation. When foam hits the surface of the walls, it increases in volume by 3–4 times. A layer of polyurethane foam (PPU) forms a high-quality thermal insulation coating.
PPU insulation is not cheap. If in other cases you can do the work yourself, then the processing of polyurethane foam on the internal surfaces of the foundation is carried out only by specialized enterprises. The undeniable advantage of this method is that large areas of walls can be treated in a short time.
Unlike slab insulation, polyurethane foam forms a seamless coating. Insulation does not require additional work to seal the seams.
The process of spraying polyurethane foam requires the use of special human protective equipment. The aerosol state of the polymer is very toxic and can cause damage to the organs of vision, breathing and skin of the installation operator. As can be seen from the top photo, work on spraying polyurethane foam must be carried out by people equipped with chemical protective equipment.
Underground ventilation
No matter how insulated the internal walls of the foundation of a wooden house are, there is a danger of an increased level of humidity in a confined space. To avoid this negative phenomenon, you need to properly organize the ventilation of the basement.
Ventilation can be natural or forced. To circulate air flows in the foundation or plinth above ground level, small through openings (vents) are made.
The vents are equipped with locking covers. With constant monitoring of the level of humidity and internal temperature, the intensity of the movement of air mass flows is regulated by the position of the locking covers of the vents.
On the basement side, the vents are covered with a fine polymer or metal mesh. This protects the basement from small animals and insects entering it.
Along with this, there are automated ventilation systems. It is advisable to install equipment of this type in large underground areas. The system maintains a stable humidity level by turning forced ventilation on and off. The equipment also regulates the operating mode of the heaters.
You can learn more about the process by watching the video:
In any case, underground ventilation is simply necessary. It is a balanced combination of insulating the foundation walls of a wooden house and underground ventilation that will ensure a comfortable environment inside the house and significantly increase the reliability and durability of the building’s supporting structures.
Warming is an event that carries several tasks. Firstly, the insulated base prevents heat loss and prevents the foundation from freezing. Secondly, thermal insulation materials protect the foundation of the house from bulging of the soil, which occurs due to freezing.
As a rule, if there is no thermal insulation for the support of the house, the first level of the structure will be damp and cold. Most often it is done outside, since this method can solve all the tasks assigned to the homeowner. Insulation from the inside is considered a less effective method, so it is used extremely rarely. Sometimes insulating materials are attached both inside and outside the base.
Benefits of insulating outside
You can resort to insulating the foundation from the inside in a wooden house only if there is good artificial ventilation of the house. If this is not provided for, the interior of the basement will acquire increased humidity. Moreover, according to professional builders, the insulation placed inside shifts the dew point, as a result of which the concrete becomes wet and freezes. This phenomenon significantly affects the durability and reliability of the foundation, destroying it gradually.
The choice of insulation method also depends on the type of base. Wooden houses, as a rule, are placed on a strip, column or pile foundation. It is customary to use extruded polystyrene foam as a thermal insulation material. This material has sufficient strength and moisture resistance. Expanded polystyrene boards do not allow water to pass through, and therefore there is no risk of moss and mold. In addition, the material is safe as it does not emit toxic substances. Expanded polystyrene is quite resistant to stress and easy to install. The slabs are easily attached to the foundation or frame underneath using construction adhesive. In addition, the plates are easily connected to each other. You can even insulate the foundation of a wooden house using polystyrene boards yourself, without the help of specialists.
Insulation of concrete tape
Insulating the strip foundation of a wooden house is a rather labor-intensive process.
- The first step is to dig a trench to the very bottom of the foundation. The width of such a ditch should be about a meter, since the blind area will be insulated at the same time. If the support of the building is very deep, then you can make a trench for the first 40 centimeters along the width of the blind area, and then reduce the width of the ditch to half a meter. If the house was built quite a long time ago, and wide cracks have already appeared on the concrete foundation, it is necessary to cover them with cement mortar. Small cracks can be sealed with a mixture of construction adhesive and cement.
- You cannot begin thermal insulation if the base has not been insulated from moisture. This must be done, since the tree begins to rot due to exposure to water and cold. You can use any available roll materials for waterproofing. Roofing felt is most often used. To attach the material to concrete, you must first cover the foundation with bitumen mastic, and then glue roofing material on top of it. It must be remembered that for effective protection, the sheets must be glued overlapping each other and additionally coated with mastic.
- Next, you can begin attaching the polystyrene boards. Most often they are installed using dowels, however, professional builders prefer liquid nails and construction glue. You can see how to insulate the foundation of a wooden house in the video.
- After attaching all the sheets to the foundation, you must fill all joints with liquid foam. Geotextiles can also be attached over the thermal insulation material. This material significantly reduces the influence of soil on the foundation.
- Upon completion of insulation, the dug ditch is filled up to the level of the blind area, then a small cushion is made of sand and crushed stone, after which insulation is also laid, concrete is poured on top, which can be combined with reinforcement for greater strength.
Insulation of the base on piles
Thermal insulation of the base on stilts is mandatory, since in this case an empty space is formed under the first floor of the house, in which cold wind can easily blow. This impact greatly affects the temperature in the house. To insulate the base of a house on a pile foundation, it is necessary to first carry out a number of works:
- arrange the basement;
- attach thermal insulation materials both inside and outside the base;
- insulate the flooring on the first floor.
You can make a plinth for a pile foundation using various methods. Firstly, you can build a thin brick wall, onto which thermal insulation material will later be attached. To construct such a brick wall, a small concrete strip is first made, the width of the brick and buried approximately 20 centimeters into the soil.
In addition, you can insulate a pile foundation using special decorative panels. In this case, a frame is made of a metal profile or timber along the perimeter of the building. Already on this frame, first the heat-insulating material is attached, and then the decorative plates. At the same time, it is important to equip a special expanded clay cushion so that moisture and cold do not pass through the soil. It is done quite simply; under the casing you need to dig a small groove into which expanded clay sand is poured, which is then covered with a layer of earth so that there is no free space between the soil and the foundation casing. It is recommended to insulate the foundation on stilts from the inside and outside in order to more effectively protect the house from the effects of cold. How to insulate a pile foundation in a wooden house can be seen in the video.
The following are used as thermal insulation materials for foundations on piles:
- polystyrene foam boards;
- Styrofoam;
- foam glass blocks;
- urea foam.
In most cases, the first two material options are used because they are cheaper and easier to install. Foam glass is an expensive material and it is not profitable to use it for a private building. As for urea foam, its installation requires special equipment, which only professional builders possess. Paying for their work also costs a decent amount.
Polystyrene foam and polystyrene are available in the form of slabs, which greatly facilitates their installation. They are attached using a special adhesive solution. If you want to use other materials for insulation, you need to select ones that do not absorb water.
Protecting the base floor box from direct contact with the ground
For more effective insulation, it is advisable to completely isolate the foundation box from contact with the soil. When the base is already fully equipped, there is usually a considerable amount of empty space left inside. If it was not initially planned to make a basement in this place, then it would be better to fill it with expanded clay or earth to the floor level. Arranging a cushion of earth is cheaper, especially if it remains after the foundation pit has been dug. However, if there is no free land and it needs to be purchased, then you need to be prepared for the fact that a considerable amount of land will be required.
In this case, it will be more profitable, simple and convenient to make a backfill from expanded clay. With its help, the entire surface of the basement is not completely covered, only half a meter from the foundation strip. This will cost much less than purchasing land for the entire area of the building. In addition, the basement will remain free, which over time can be used as desired.
Thus, you can insulate a wooden house in various ways, it all depends on the type of foundation and design features. In any case, it is necessary to use thermal insulation materials, as they will help provide the entire structure with reliable protection from cold and exposure to external conditions. It must be remembered that despite the strength of concrete, it is quite easily and quickly destroyed under the influence of moisture and cold.
If the project has an exploitable basement underground level, it is better to insulate the foundation of the house from the outside. This is guaranteed to eliminate fogging of the internal walls and additionally protect the waterproofing layer from mechanical damage. It makes no sense to insulate the foundation strip from the inside, although a similar technology is used in.
In order to better insulate the foundation of a building with a minimum construction budget, it is necessary to understand what factors act on it from the outside (option with a basement) or from both sides (MZLF without a basement). After that, all that remains is to choose a heat insulator with a service life identical to the resource of reinforced concrete structures.
Thermal circuit of the underground floor
Characteristic features of the operation of underground power structures of a house are:
- freezing of adjacent soils outside;
- excessive saturation of these soils with groundwater, rain and flood waters;
- positive temperatures from the inside.
During frosty, uneven swelling of wet clay, tangential forces arise that tend to push the tape out. When in contact with wet soil, concrete is also saturated with water, which increases in volume when it freezes. This is fraught with multiple microcracks in the load-bearing structure, which increase every year.
If you insulate the foundation extruded polystyrene foam outside, you can solve several problems at once:
- move the thermal circuit along with the exact dew outward - there is guaranteed to be no condensation on the internal walls;
- it is better to protect the waterproofing from damage by intumescent soil - the concrete will not get wet;
- insulate the structure - the concrete will not be able to freeze even when wet.
Insulating the basement of a house from the inside will not be able to solve any of these problems. In addition, under the base of a heated building, by default, the geothermal heat of the subsoil is retained; the soil cannot freeze, even in the absence of thermal insulation.
Attention! Polystyrene foam, glass or basalt wool cannot be used for thermal insulation of underground structures. Mineral wool loses its properties when wet, PSB-S (foam plastic) has a low resource. It is necessary to use high-density polystyrene foam of the XPS and EPPS brands.
A conventional blind area, consisting of a concrete screed and facing material (paving stones, paving slabs), partially solves the problem of frost heaving:
- moisture is removed from the building, the soils adjacent to the foundation from the outside are not saturated with rain and flood runoff, dry clay cannot swell
- however, there is soil moisture and groundwater in the ground that can moisten the clay by capillary action, restoring the likelihood of heaving forces.
Internal thermal insulation measures are implemented in situations where the installation of insulation outside the basement or basement does not bring the desired effect or is difficult for some reason.
The relevance of carrying out these works is due to the maintenance of a constant temperature regime inside the premises located in close proximity to the ground, and the insulation of floors in the structure.
However, it should be borne in mind that insulating the foundation from the inside is not able to prevent damage to the foundation caused by regular harmful effects of moisture and environmental factors.
Features of the procedure and variety of implementation methods
Currently, there are several types of base insulation, each of which, in some cases, is used in conjunction with the internal lining of the basement or plinth. In any case, before carrying out work on placing insulation, it is worth taking care of high-quality waterproofing of the foundation. At the same time, it is better to give the greatest preference to methods of protection that will give the entire concrete structure resistance to moisture, for example, penetrating or rubber waterproofing.
A dry concrete foundation is less susceptible to freezing, which means it will maintain its integrity for a significant period of time.
Methods for installing insulation
Technologies for carrying out internal work on insulating the base are similar to the external installation of thermal insulation sheets. The most common ways are:
- sprinkled with expanded clay - a light porous material made by firing shale and clay (reduces freezing rates of the floor of the first floors, but is an ineffective remedy in permanent residences);
- installation of thermal insulation boards made of polystyrene foam, polystyrene foam and polystyrene with finishing cladding (one of the frequently used methods of installing thermal insulation, usually used when placing thermal insulation together on the outside of a building made of a homogeneous material);
- spraying polyurethane foam (a fairly effective method of arranging thermal insulation, installed both as an additional and independent insulation, capable of creating a monolithic thermal insulating coating with high adhesion; the use of this method is implemented by involving specialists with special equipment).
Features of application
At the stage of choosing the listed methods, emphasis should be placed on the following points:
- the functional purpose of the structure and the dimensions of the facing surface;
- the presence of an external thermal insulation layer and street temperature indicators;
- soil type and groundwater level;
- expected temperature level, as well as the presence of ventilation and heating systems in the insulated room;
- the need for subsequent designer cladding.
Expanded clay is the most budget-friendly insulating material The most cost-effective way to perform thermal insulation is to sprinkle the underground space with expanded clay chips. This material perfectly removes moisture and, due to its porous structure, creates an air layer that maintains a constant temperature and prevents the penetration of cold air currents.
The powder can be used to fill both the underground space and a special gutter-formwork erected indoors in close proximity to the surface of the walls.
In the case of arranging basements for household rooms, the foundation walls must not only be covered with a layer of insulation, but also cladding. In such a situation, it is necessary to prepare and level the surface as much as possible for finishing, so it is most rational to use slab materials.
Since in such equipped basements it is necessary to maintain a constant temperature, when decorating them it is necessary to take care of the additional installation of homogeneous materials on the outside of the walls.
The polyurethane foam method is excellent for any type of basement, but its pricing policy is somewhat different from the methods described above.
Sprinkling with expanded clay
In most cases, this technology is used when insulating the foundation of a wooden house, country house or garden. Expanded clay is widely available in many hardware stores at a reasonable price, while the backfilling process does not require special skills and can be done with your own hands.
Procedure for sprinkling with expanded clay:
- Along the perimeter of the foundation walls at a distance of 30-40 cm, formwork is made from any available wooden materials. The height of the formwork structure is from the ground to the surface of the first floor slab.
- Wooden elements used in the manufacture of formwork are pre-treated with antiseptic compounds to protect wood in direct contact with the soil. The formwork is fixed by installing slopes.
- Before filling the expanded clay, a polyethylene film is laid on the bottom of the formwork, the essence of which is to provide waterproofing protection.
- We fill the formwork with expanded clay chips.
The height of the expanded clay cushion is equal to the height of the formwork. In the case of construction on moisture-containing soils, in addition to the described procedure, it is recommended to apply powder under the floor, after laying a plastic film around the entire perimeter.
Slab insulation
As an example, let's take slabs made of polystyrene. The named material is a synthetic thermoplastic amorphous polymer, the next in the line of modifications of foam plastic elements.
Modern manufacturers of boards from such raw materials produce polystyrene foam material of different brands, differing from each other in structure density, impact resistance and thickness. For internal insulation of the base, it is enough to use slabs with a thickness of 5 to 10 cm.
This method is suitable both for insulating the foundation of a wooden house and for buildings made of other materials. To finish the foundation with polystyrene slabs with your own hands, you must follow the following procedure:
- Check the walls for rough irregularities, cracks and dirt, and if necessary, eliminate all defects (seams and cracks are cleaned down to the base, after which they are covered with a layer of waterproofing and finishing putty).
- Install waterproofing depending on the purpose of the building and the type of soil.
- Install polystyrene boards. Each element is fixed with a special glue. The adhesive is diluted manually and then applied pointwise to the slab. The optimal number of dots is 8-10 pieces, then the sheet is pressed tightly against the surface to be pasted. For ease of laying and reliable connection, the slabs have special grooves that must be aligned during installation.
- After the adhesive has completely dried, the polystyrene sheets are additionally fixed with dowel nails with a wide rounded head. The procedure involves drilling holes with a depth that ensures reliable fastening of all component layers.
The optimal penetration into concrete should be about 5-6 cm. In order not to make a mistake with this indicator, you should measure the thickness of all layers and set a limiter on the hammer drill. Next, dowels are driven into the holes and then nails.
- Since polystyrene boards are susceptible to rodents, it is necessary to place a reinforced mesh outside the installed boards, the installation of which is carried out using cement glue.
- The finishing layer of plaster is applied and after it has dried, they proceed to placing decorative coatings.
Polyurethane foam insulation method
Currently, this is one of the most effective ways to organize the insulation of premises, implemented by spraying foam liquid under high pressure. When hardened on the outside, a foam layer with a closed porous composition is formed, which has high resistance to moisture and is devoid of seams.
Watch the video on how to properly spray an insulating compound onto the base of a house from the inside.
The procedure for applying the polyurethane mixture is carried out without any preliminary surface preparation and is implemented in the shortest possible time.
One of the significant disadvantages of this method is its inflated cost, however, during the operation of a building with excellent hydro- and thermal insulation characteristics, the method more than pays for itself.
Conclusion
In conclusion, I would like to once again draw attention to the need to insulate the foundation from the inside, since this is the key to the strength and durability of the entire structure, as well as maintaining a constant temperature regime.
By taking care of its high-quality protection with your own hands during the construction stage, you will ensure warmth and comfort in your home for many years.
