Floor insulation in a wooden house from below

The content of the article

One of the problems of living in a private wooden house is the cold floor. The fact is that air currents of low temperature go down, coolness also comes from the earth. Make the home cozy, warm and comfortable, protect it from freezing will help insulation of the floor covering, which is performed using a variety of materials.

How to insulate the floor in a wooden house from below

It is known that the house is the fortress of every person, therefore, comfort and warmth should always be felt in it. One way to transform the living space is to insulate the floor in a wooden house from below. To get a positive result, you should carefully read the assortment of products for insulation, find out the features, choose the best option and complete the installation.

Installation of a thermal insulation layer is distinguished by several specific nuances:

  1. A two-layer insulation of the floor in a wooden house from the bottom is necessary. It is necessary to reduce the loss of heat passing through the rough bottom. As a rule, the floor is made of ordinary boards, which are fitted to each other. The surface will suffer from the strong influence of humidity and low temperature from the ground, so building materials must be treated with special tools in advance.
  2. Given the fact that wood absorbs liquid well, waterproofing is required. Before starting to insulate the flooring, it is recommended to lay a single-sided fiber.
  3. Products for floor insulation in a wooden house from below should not change their characteristics when in contact with wood.

The design of the wooden floor with insulation

What insulation is better for the floor in a wooden house

Very often, consumers think about what material is more profitable to use to make insulation of a cold floor in a wooden house from below. The choice of insulation depends on such factors: the size of the room, type of surface, wood species, climate, price. It is worth saying right away that expensive finishing material is not always the best in quality and may simply not be suitable for a particular building. To make the right choice, it is recommended to find out what insulation floor materials are, to study their characteristics, advantages.

Materials for thermal insulation

The range of modern thermal insulation is very wide. Products may differ in size, characteristics, installation technologies and so on. The insulation of floors in a wooden house is often carried out by such building materials: mineral wool, expanded clay, expanded polystyrene, polystyrene (polystyrene foam), polyurethane foam, sawdust, and foam. The choice of heat-insulating layer depends on the individual preferences of the owner of the building and the characteristics of the flooring. How to insulate the floor in a wooden house during the construction or repair of a residential building?

Mineral wool

Cold wood flooring is often insulated with mineral wool. This type of sealant is available as elastic mats or durable panels. The material must be laid in a single layer. The main advantages of mineral wool:

  • high sound and heat insulation;
  • long term practical use;
  • resistance to fire and high humidity;
  • affordable cost;
  • environmental friendliness;
  • this insulation is resistant to damage: mechanical and chemical influences.

mineral wool floor insulation

Polyurethane foam

The ideal seal for a wooden floor, the pores of which are covered with air and gas for insulation, is polyurethane foam. This cellular material has a small mass, but it retains heat well. Such a heater is maximally resistant to the formation of fungus, mold, is not afraid of decay, and is not susceptible to acids. Polyurethane foam is applied using a special technique and is characterized by good adhesion (adhesion to the surface). Thanks to the use of this type of thermal insulation, it is possible to insulate a floor of any shape without forming joints.


Thermal insulation of floors using polystyrene (polystyrene foam) has a large number of advantages. The structure of the material provides a low level of vapor permeability and thermal conductivity, fire resistance, reliability, resistance to the influence of chemical and biological factors. Expanded polystyrene has a long shelf life and retains its characteristics for a long time. The main disadvantage is that the sealant absorbs a certain amount of liquid, which may affect some properties..


Warming of the wooden floor is also carried out with foam – a very light polymer homogeneous material that does not exert a load on the base of the building. It is obtained by extrusion – pressing molten raw materials through the molding cavity of the extruder (special equipment). Penoplex is very strong, resistant to low temperatures, durable, has a minimum moisture absorption and combustion.

Expanded clay

Thermal insulation of a wooden floor can be carried out by means of expanded clay – loose, porous products, which consists of small round balls. Insulation is made by burning shale or clay in a special furnace. Expanded clay for preserving the heat of the wood floor is a durable and environmentally friendly material. It has high rates of sound insulation, fire resistance, frost resistance. There is one significant minus: after a certain period of time, expanded clay compacts under the weight of its own weight and loses the quality of thermal insulation.

expanded clay floor insulation


A roll-type insulation for a wooden floor, which is made of foamed polyethylene, which is coated with aluminum foil on top is a penofol. Such a sealant is not very thick (3-10 mm), but it conducts heat well and does not need to be laid for additional vapor barrier. Because of its composition, penofol has several disadvantages: rust can “eat” the foil, and polyethylene loses its strength over time.

Installation technology

A reliable and effective option for laying insulation for wood flooring below is to install on the logs – transverse boards (boards) on which the floor covering is located. A.

  1. First, logs are attached to the brick foundation, the distance between which should be 1-1.2 meters (as in the photo).
  2. Chipboard or thick plywood is mounted on the bottom bars using self-tapping screws. This is necessary for laying thermal insulation.
  3. Thermal insulation material is spread on the surface between the lags. The thickness of this layer of thermal insulation is diverse, so you need to be guided by the dimensions of the transverse boards (lag).
  4. Waterproofing is placed on top of the sealant (for example, a plastic film). This type of material is not always used, because some types of insulation are themselves resistant to moisture..
  5. The final stage of installation is the installation of elements of an old or new wooden floor covering on the ground floor.

lag mounting

Where to order and how much is the thermal insulation of floors

You can purchase products that can be used to insulate a cold wooden floor in various places: on the construction market, in specialized stores, through online resources. Below is a table with an approximate average price for the country:

Name of insulation

The cost in rubles per 1 square meter

Mineral wool


Expanded clay








Polyurethane foam


Learn more about how vapor barrier is applied to walls of a wooden house.

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