Mineral wool screed. How to insulate a concrete floor in a private house: choosing insulation, installation methods and do-it-yourself insulation of a concrete floor

Thermal insulation of the floor is one of the mandatory stages of home improvement. Without properly executed thermal insulation, comfortable living in the premises is out of the question. Therefore, it is very important to responsibly and competently approach both the process of choosing a material for insulating a concrete floor, and directly to the installation of thermal insulation.

At the stage of choosing a material for floor insulation, it is necessary to pay attention to some important characteristics.

1. Density. The weight of thermal insulation directly depends on it. The less dense the insulation, the more pores it contains and the greater the amount of heat will be retained inside the room.
2. Strength. It is better that the strength of the material is as high as possible.
3. Thermal conductivity. This coefficient reflects the ability of thermal insulation to transmit heat. It is better for this indicator to be as low as possible.
4. Moisture resistance. The higher it is, the better.
5. Moisture permeability. This figure should be minimal. Otherwise, the insulation will very quickly become saturated with moisture, against which its thermal insulation characteristics will noticeably deteriorate.
6. Durability. At this point, everything is very clear: the greater the durability, the longer the selected material will last.
7. Environmental friendliness. Those who plan to build an environmentally friendly building using natural and completely safe materials should pay attention to this parameter.

Popular insulation materials for concrete floors

The following is a simple table in which you can consider the main characteristics of existing insulation materials. Be sure to take them into account when choosing a material in order to choose the insulation that is best suited specifically for your concrete floor.

There are several main methods of thermal insulation of a concrete floor. Each of these methods can be used at a strictly defined stage of floor installation.

So, when creating a floor “from scratch,” the thermal insulation material is laid under the screed. If the floor in your home is already finished, you can turn your attention to a system called “warm floor”. It makes it possible to provide high-quality heating of the surface over its entire area. An excellent solution is to replace the crushed stone in the mixture with perlite or expanded clay with similar properties. But this option, like the first, is relevant only when arranging a floor structure from scratch.

A very popular thermal insulation option is construction of the so-called "raised floor". This technique is based on the construction of wooden logs, the free space between which is filled with a heat insulator.

For additional insulation of the floor, you can use a special “warm” covering, for example, carpet. However, this method should not be considered as an independent, full-fledged thermal insulation.

Each method given above is applied depending on the conditions of a particular situation. They are often combined with each other to achieve maximum effect.

Proper thermal insulation consists of several layers. In cross-section, such a design will look like a kind of pie. Regardless of which method of thermal insulation will be used, work must begin with certain stages.

1. If repairs and thermal insulation of a concrete floor are being carried out in an already erected building, the old screed must be completely dismantled, then the sand and gravel cushion must be refilled and compacted thoroughly.
2. Fill the resulting cushion with a layer of “lean” concrete, which will act as a base for heat and moisture insulation.
3. Wait until the concrete base gains strength and hardness, and lay waterproofing material on it.

Waterproofing should be as reliable as possible. Even the slightest mistakes can lead to serious consequences.

Try to do everything with maximum compliance with the instructions. Any mistakes can lead to moisture penetrating into the thermal insulation, and this will have an extremely negative impact on its performance properties. After some time, the moisture will reach the finishing screed, which will lead to an increase in air humidity in the room. The floors will always be cold, and the screed itself will soon collapse. To avoid all these negative consequences, The waterproofing material must be laid in an overlapping manner and all joints must be taped.

After completing the installation of the waterproofing material, you can safely begin laying the insulation. Plates and mats are fixed using special glue. The materials themselves should be placed in space. This approach allows you to reduce the risk of cold bridges and achieve higher strength of the insulation layer. Along the perimeter of the thermal insulation, as well as between the edges of the material and the wall surface, you need to place a damper tape.

It is important to know that a heat insulator such as polyurethane foam can be laid in the form of slabs, and also applied by spraying. The second option allows you to obtain a seamless thermal insulation layer with better characteristics. Polyurethane foam requires mandatory installation of hydro- and vapor barriers.

After the main thermal insulation material has been completely laid, you need to fix another layer of moisture insulation on top of it, place a reinforcing mesh on it for greater structural strength, and then pour a rough screed from concrete mortar. At this stage of the work, you can perform additional insulation of the concrete floor by replacing crushed stone with perlite or expanded clay.

If you decide to do this, remember that perlite and expanded clay are characterized by specific performance properties, due to which such insulation materials are recommended for use in “semi-dry” concrete screed. It is better that the mixture contains filler from as many different fractions as possible. This will allow you to achieve the most dense filling of the solution and will significantly increase the strength of the screed.

The screed must dry completely and gain the required strength. Only after this will it be possible to begin installing the finishing coating. At this stage, it is also possible to increase the thermal insulation properties of the floor. You just need to lay a special insulating substrate and select materials that are characterized by normal thermal conductivity. The substrate in this case is foamed polyethylene or cork material.

Take into account the fact that a particular type of flooring can only be combined with a certain type of underlay material.

For example, foamed polyethylene cannot be combined with linoleum; in this situation, cork is better suited. So before purchasing a reinforcement liner, be sure to check with your sales consultant to see if it is compatible with the finish you have chosen.

To achieve maximum thermal insulation and create the most comfortable living conditions, it is recommended to install an electric or water heating system.

The water system is more complex to arrange. It requires not only the installation of pipes under the screed, but also the installation of special equipment designed to heat and ensure forced circulation of water.

The heating system is installed directly on top of the thermal insulation material. It is important that the insulation has a foil coating, due to which more heat will be reflected into the room. If there is no foil barrier, it is recommended to lay it manually.

The system is installed according to the instructions provided by the manufacturer. After checking its performance, you can lay a reinforcing mesh to strengthen the structure and begin arranging the screed. When using a “warm floor” system, the solution can be prepared without crushed stone, expanded clay and other fillers.

A similar insulation option can be used on the upper floors of a house consisting of several floors. In such conditions, you need to monitor the thickness of the thermal insulation layer. With every centimeter of height taken away from the room, the conditions in it will become less and less comfortable.

Insulation of a concrete floor using a raised floor system. Procedure

1. At first the floor surface is thoroughly cleaned of any dirt, and then, if necessary, it is leveled.
2. By room area logs are installed. A wooden beam 5x10 cm is suitable for them. The logs should be mounted at a distance of 0.5 - 0.6 m from each other and about 0.1 - 0.15 m from the walls.
3. Stacked on top waterproofing material. A simple plastic film will do. Pieces of material must be overlapped, not forgetting to seal the joints with tape.
4. Inside thermal insulation is arranged. Mineral wool, polystyrene foam, perlite and almost any of the previously discussed insulation materials are perfect.
5. Chipboard or moisture-resistant plywood is placed on the logs, after which The finishing coating is being installed.

Consider the fact that due to a raised floor, the height of the room can be significantly reduced. Therefore, before using this method, consider its feasibility several times.

Thus, there is nothing particularly difficult about insulating concrete floors yourself. You just need to select suitable thermal insulation materials and determine the optimal method of their installation. Stick to technology, remember the main rules and nuances, and the thermal insulation you create will reliably prevent heat loss. Good luck with your work!

The need to insulate floors, through which a significant portion of heat loss occurs, is undeniable. For this, various technologies are used, including insulation on the floor under the screed.

Requirements for insulation under screeds

Insulation under a concrete screed must have:

• rigidity and increased strength, reliably withstanding the weight of cement-sand mortars, finishing, pressure from the weight of furniture and the passage of living people;
• low dead weight, which will not require reinforcement of the floor;
• moisture resistance - the moisture contained in it should not penetrate into the insulation;
• resistance to decay, mold and fungal microorganisms;
• low thermal conductivity;
• optimal thickness, which does not lead to a significant reduction in the height of the free space of the room;
• environmental friendliness;
• a minimum of necessary protective measures and ease of installation work.

How to choose the optimal insulation?

There is a wide variety of materials on the heat insulator market. The most popular are:

• polyurethane foam;
• isolon;
• expanded clay;
• semi-rigid and rigid panels.

When asking the question which insulation is better for a floor screed, you need to consider:

1. Type of base. You can use any of the above insulation for concrete floors under screed. Many experts recommend spray polyurethane foam. On the ground, it is recommended to use expanded clay or foam boards. For wooden floors - ecowool, insulation or penoplex (it is better to cover with light dry screeds).
2. Type of floor. All specified insulation materials can be used for all finishing floor coverings. The screed covering the top does not require that the material “breathe” and protects the foam well from fire, which releases harmful gases. When installing heated floors, it is recommended to use heat-reflecting foil.

High physical and technical characteristics lead to a higher cost, but saving on thermal insulation of floors is not advisable. Modern insulating materials are produced on high-quality equipment using the latest scientific achievements and are distinguished by truly unique properties.

The importance of preparatory work

Regardless of the choice of thermal insulator, careful preparation of the base is necessary for high-quality thermal insulation.

1. The concrete floor is cleaned of dirt, sinks, cracks and potholes are sealed. The surface is leveled by cutting off the protrusions.
2. On the ground, a reliable and durable foundation is first laid out from a well-compacted sand cushion and a layer of lean concrete.
3. Wooden floors are repaired, traces of rot, mildew and mold are removed. Processed

It has been verified that the insulated floor is not only very comfortable to use, but also practical. In order for it to serve as long as possible and the result to meet expectations, it is necessary to choose the right insulation for the floor screed.

The main purpose of insulation is to prevent cold from entering the room (in this case from below). By using insulation, a reduction in the cost of heating a room during the cold season is achieved.

Requirements for insulation

Due to the fact that insulation under floor screed is used in different climatic zones, they must have the following properties:

• water-repellent;
• high strength properties (to prevent the appearance of deflections and subsequent deformation of the floor covering);
• meet fire safety requirements;
• have a low thermal conductivity coefficient.

Materials for screed insulation

When deciding which type of insulation to choose, keep in mind that for each type of construction in a certain climatic zone, the material for the floor screed is selected individually.

Expanded polystyrene and foam plastic

Recycled material (recycled polystyrene foam). Used in construction and repair work. It has high compression resistance, does not decompose, and is practical to install.

In addition, among the advantages of expanded polystyrene it should be noted:

• prevalence;
• cheapness;
• low thermal conductivity coefficient.

The disadvantages include:

• low fire resistance;
• low porosity (which promotes moisture accumulation on the surface);
• long period of decomposition (causes significant harm to the environment);
• the presence of impurities, the evaporation of which is harmful to health.

Despite the fact that manufacturers indicate the service life of polystyrene foam is 50 years. The first signs of wear appear much earlier.

Used for floor insulation and foam. Its peculiarity is that it can “play” when installed. Cutting it in places under which there are voids helps to avoid this. However, it will still not be possible to achieve a perfect fit of the foam to the floor surface.

Eco-friendly and natural material, which is made from clay-based composites. It is the most suitable option when it comes to insulating the floor on the ground. Since this type of insulation undergoes heat treatment (firing), it is durable. By varying the size of the granules, you can select the required level of thermal conductivity. In addition, this material is an excellent soundproofing material.

The advantages of expanded clay include:

• prevalence;
• low cost;
• porous structure;
• environmental friendliness;
• durability.

Of the significant disadvantages, we note one - in areas with a predominantly cold climate, the required layer of expanded clay is up to 15 cm. This height of insulation significantly reduces the area of ​​the room.

Foil insulation

Insulation covered with a thin layer of foil. The foil coating can be on one or both sides. It is most often used as insulation of walls and ceilings of rooms, but can also be used for insulation of floor coverings and under a heated floor system.

Despite the fact that this material has good thermal conductivity properties, the use of foil insulation under floor screed is impractical due to the high density of the material. The absence of a porous structure leads to the appearance of condensation, further accumulation of moisture, which leads to deformation of the coating and the appearance of fungus in the room.

Do not forget about the foil coating, which reacts with liquids and chemical elements. The occurrence of reactions with unprotected aluminum entails its destruction.

Foil insulation has the following advantages:

• low thermal conductivity;
• availability;
• lack of water absorption (suitable for insulating rooms and bathhouse structures).

Flaws:

• labor-intensive floor installation due to high requirements for laying a layer of foil insulation;
• lack of natural air circulation;
• flammability;
• destruction of foil under the influence of external factors.

Mineral wool

This insulation is common in various fields of construction. Meets all requirements for reliability and safety. It is an environmentally friendly material, able to withstand high temperatures and changes in ambient temperatures. It has a fairly high density. The use of this type of insulation is possible under various types of screed (dry, wet, under floating floors on which large equipment is installed).

Mineral wool has the following positive characteristics:

• fire safety;
• high thermal insulation performance;
• frost resistance;
• vapor permeability;
• high compressive strength;
• soundproofing properties;
• accessibility;
• ease of use.

But it has the following disadvantages:

• Requires additional space in height.
• Some types of mineral wool (glass wool) require additional insulation due to its flowability.
• In some cases, a waterproofing coating is required (for types of insulation that lose their original properties when exposed to moisture).

Glass wool is rarely used for insulation.

Waterproofing rough screed

The use of waterproofing is necessary primarily to protect the room from moisture and to preserve the properties of the insulating material.

Waterproofing is used in the construction of various premises and in the arrangement of floors that are located on the ground.

Various polyethylene sheets, preferably rolls, are usually used as insulating material.

When installing waterproofing, adhere to the following points:

1. Rolled sheets are laid overlapping, after which their joints are carefully worked out (with construction tape);
2. It is necessary to ensure the integrity of the coating.

Note! The waterproofing of the rough screed is laid with a margin on the adjacent walls. (After completing the final screed, the screed is removed).

Laying the material is possible both in front of the rough screed and on top of it.

Options for floor insulation under screed: installation procedure

Insulation under the screed with penoplex and polystyrene foam. In the process of building a floor, the pad is first prepared. To do this, a layer of gravel is laid evenly and then pressed. Then a cushion of sand is poured, which is also pressed. After these operations, a concrete screed is poured over the ground onto the reinforcement frame. The prepared floor can be covered or not covered with waterproofing, since polystyrene foam itself performs the function of waterproofing. A damper tape is installed along the edge of the room. The next layer is insulation. In most cases, it is mounted in a checkerboard pattern. Next, the insulation sheets are filled with concrete screed.

Video: laying foam plastic under the screed

Video: how to make a screed using polystyrene foam

Insulation expanded clay. First of all, the concrete surface or soil is covered with a vapor barrier material. Next, the area is covered with expanded clay of different fractions (to achieve maximum thermal insulation efficiency). The finished layer is treated with cement laitance. After completing the above operations, the insulation is poured with a cement screed over the reinforcing mesh.

Note! This type of floor acquires its strength properties no earlier than a month after installation.

Video: floor screed technology with expanded clay

We have already talked about insulation with foil insulation. Its use is not advisable under floor screed, even in combination with a heated floor system. See what happens to the foil a month after pouring the screed.

Stages of insulation using mineral wool no different from the previous ones. Only the laying technology differs depending on the underlying surface. So, to cover compacted soil, mineral wool is tightly installed between the joists. A rough or reinforced screed is laid on top. To cover the rough screed or floor slab, a layer of vapor barrier material is placed below and on top of the wool layer, the joints of which are sealed with tape.

Video: laying mineral wool under the screed

Concrete floors are associated with solidity, durability and reliability. But they also have a drawback - they are cold. The high thermal conductivity of reinforced concrete removes heat from residential and domestic premises. Therefore, high-quality thermal insulation is necessary for concrete floors. For this, different materials are used - fibrous, foamed plastics, bulk plastics, etc. Having general construction skills, the homeowner can cope with insulation on his own.

Why insulate the floor

Among the total heat losses, the floor occupies a prominent place - up to 15%. A cold floor not only “steals” kilocalories of heat - it significantly reduces the comfort for those living in the house. If your feet are cold, the general feeling of cold intensifies. Cold floors are especially dangerous for young children, who often play sitting and lying down, and for older people.

The cold coming from the floor harms pets and indoor plants. Large heat losses have a number of other unpleasant consequences: moisture can condense on cold surfaces and the relative humidity will increase. This will lead to the appearance of mold and mildew, which are extremely harmful to human health. Therefore, in addition to thermal insulation, it will be necessary to take care of the vapor and waterproofing of the ceiling.

Determining heat leakage paths

Heat leaves rooms in two ways - by heat transfer through concrete and with drafts through joints with walls. Accordingly, when insulating the floor, you need to block both of these paths by selecting and installing suitable thermal insulation materials.

Selection of material for floor insulation.

The thermal insulation material must have a low ability to conduct heat. It is characterized by the coefficient of thermal conductivity. The lower it is, the better the material insulates.

In addition, the material must:

• be durable;
• do not lose properties when moistened;
• easy to install;
• have a reasonable price.

Today the most popular thermal insulators are:

• Fibrous. Basalt, glass and slag wool.
• Monolithic. Foamed plastics in panels, plywood, OSB, etc.
• Sprayable. Polyurethane foam and ecowool, applied using the wet-adhesive method.
• Bulk. Dry ecowool and traditional - expanded clay, sawdust, shavings.

How to choose the most suitable material for thermal insulation?

Mineral wool

Basalt wool is made from volcanic rocks. Its fibers are short and stiff, and its density is high. Kt= 0.034…0.039 W/(m*K).

Advantages:

• Strength. Withstands heavy loads, used for flat roofs and interfloor floors under screed.
• Low hygroscopicity. When moistened, it does not lose its properties.

Basalt wool

Flaws:

• Low elasticity. Difficult to install by surprise.
• Large mass of insulation. It is necessary to calculate the load-bearing capacity of the floor and, possibly, strengthen it.

Supplied in the form of mats 1200*600 mm.

Glass wool is made from glass production waste; its fibers are long and elastic. Density is lower than that of basalt wool, Kt =0.032…0.041 W/(m*K)

Advantages:

• High elasticity makes cutting and installation easier.
• Low density makes it possible not to increase the load-bearing capacity of the floors.

Glass wool

The disadvantage of glass wool is its high hygroscopicity. When wet, the material loses its thermal insulation properties. Available in both mats and rolls, more convenient when laying over a large area

Expanded polystyrene

The common name for the material is polystyrene foam. It is foamed polystyrene, supplied in the form of sheets of different thicknesses. Kt 0.038-0.052 W/(m*K)

• very light;
• cuts well.

Cutting foam

• Fragile.
• It's crumbling.
• The joints must be additionally sealed, for example, with polyurethane foam.

Foamed polystyrene using extrusion has the best thermal conductivity Kt = 0.029-0.032 W/(m*K). It is more durable and is available in tongue-and-groove sheets, which makes it easier to install joints. Does not absorb moisture at all and does not require additional vapor and moisture insulation.

Extruded polystyrene is often called “penoplex”, after one of the most common brands.

Foamed polyethylene

This insulation is very popular for insulating and waterproofing concrete floors; it is laid under laminate, parquet boards, and linoleum. Kt=0.035-0.037 W/(m*K).

The material has undeniable advantages:

• Easy.
• Elastic.
• Easy to install.
• Insensitive to moisture.
• Perfectly isolates sound and vibration.

Penoizol or polyethylene foam

The disadvantage of insulation is its high price. Available in the form of mats (thick) and rolls, sometimes foil. The canvases are glued together with double-sided tape.

Spray polyurethane foam

Polyurethane is sprayed onto the heat-insulating surface in liquid form, foams and hardens on it, forming a continuous layer. The texture resembles construction foam. It has excellent heat-insulating properties - its Kt = 0.023 W/(m*K).

Advantages:

• Low thermal conductivity.
• No joints or seams.

Polyurethane foam coating on concrete floor

The following disadvantages limit the widespread use of insulation:

• High price of equipment. Very high.
• High requirements for the qualifications of the spraying plant operator.
• Requirements for air temperature during application.

Plywood, fibreboard, chipboard and others

Such materials are used as insulation only for thermal insulation of the second floor, above heated rooms. Kt =0.12...0.15 W/(m*K), which is three to four times higher than other popular materials. When using chipboard as a thermal insulation material, it is necessary to perform vapor and waterproofing especially carefully. When wet, chipboard swells and can warp the finish coating.

Ecowool

The increasingly popular insulation for concrete subfloors is made from recycled or recycled cellulose fibers. Kt=0.032-0.041 W/(m*K)

The composition of ecowool contains a bioprotector that suppresses the development of mold, fungi and microbes, and a substance that prevents combustion.

Fluffed ecowool, ready for application

Advantages:

• does not burn;
• light;
• does not emit harmful substances, including in case of fire;
• is blown into the narrowest cracks, openings and voids of insulated structures.

The disadvantages of ecowool include:

• high cost of spraying equipment;
• the need for highly qualified workers.

Application of ecowool manually using a dry method

To insulate concrete floors, you can also use the manual method of applying the material - grinding it with a construction mixer in a vat and simply pouring it onto the insulated surface. Material consumption using the manual method is 20-30% higher, but expensive equipment is not required.

Traditional materials

Thermal insulation properties of natural materials, such as:

• shavings;
• sawdust;
• reed mats;
• peat slabs;
• pressed flax and hemp fiber.

cannot compete with industrially produced insulation materials. Although they saved our ancestors from the cold for thousands of years.

Their advantage will be environmental friendliness and low cost.

Pressed flax fiber

The disadvantages are the following:

• poor thermal insulation;
• hygroscopicity;
• susceptibility to rot, mold and mildew;
• flammability.

When building a log house from imported logs, a large amount of sawdust and shavings are formed on the site. It is reasonable to use this waste for floor insulation. You will only need to take care of their impregnation with a fireproof and bioprotective solution, as well as steam and waterproofing.

Bulk materials for thermal insulation

This is also a cheap way to insulate. The most popular material of this type is expanded clay, obtained by firing a clay mixture. Its porous granules are inexpensive and provide Kt=0.1 W/(m*K).

The advantage of expanded clay is its environmental friendliness, non-flammability and ease of use. The disadvantage is the high thermal conductivity and the need for labor-intensive cement screed, which significantly increases the cost of the solution.

Expanded clay

Less commonly used are other bulk materials - foam glass, vermiculite, foam or polystyrene foam chips. They are better for insulation in conditions of a limited budget.

How to insulate a concrete floor

The technology for thermal insulation of floors is simple, but all the requirements of the technological process must be strictly followed. An attempt to save time will lead to ineffectiveness of the entire insulation. When choosing a method of insulation, you should take into account the method and degree of thermal insulation of the foundation, basement and blind area. How to properly waterproof and insulate a concrete floor? The technology depends on the selected material.

Fibrous materials

The main thing when working with mineral wool is not to forget about steam and waterproofing, joints and fits. The thickness of the layer is chosen depending on the climate zone; in regions with a mild climate, 50 mm is enough; in frosty places it is better to lay 150.

• Lay a vapor barrier membrane and connect the joints of the panels with metallized adhesive tape.
• Install logs. Their height should coincide with the selected thickness of thermal insulation, the pitch should match the dimensions of the slabs or rolls of mineral wool. Plates or rolls must fit between the guides without gap.
• Lay insulation. Particular attention to joints and abutments to walls.
• Place a vapor barrier membrane over the slabs, smooth side up. The membrane will remove moisture.

Laying basalt wool over a waterproofing membrane

• Lay tongue and groove or thick plywood. Secure to the joists with self-tapping screws.
• Next, you can lay the final finish: laminate, parquet board, cork or linoleum.

Expanded polystyrene

Foamed polystyrene is often used under cement screed. The material is not hygroscopic, it can be used in wet rooms - kitchens, bathrooms, bathrooms, saunas.

• Prepare the concrete surface. Seal cracks, crevices and potholes, and level out protrusions.
• Clean from oil and grease stains and other contaminants.

Important! Alignment requires more careful than in the previous case. It is necessary to either concrete the insulated floor with a leveling solution, or fill the surface with fine sand and carefully level it.

Insulation with extruded polystyrene foam under the screed

• Lay the insulation boards end to end over the entire floor area.
• Tongue and groove slabs are laid using protrusions. The joints of the foam boards are sealed with polyurethane foam.
• Lay and glue damper tape along the entire wall line, allowing the screed to expand and not break during temperature fluctuations. The tape can also be nailed to wall blocks in aerated concrete houses.
• Roll out polyethylene over the insulation layer no thinner than 0.5 microns, with an overlap of 10-20 cm, and glue the sheets with double-sided tape. This layer will prevent moisture from leaking out of the cement screed.
• Place the fittings. If the room has a water-heated floor, install pipes, fittings, etc. on top of the reinforcement system.

Installation of heated floors and fittings

• Fill the screed.

Sprayed materials

This method will require purchasing or renting expensive equipment. Most owners only rent out units with qualified operators. Manufacturers also produce disposable, non-rechargeable kits for self-use.

• Prepare the concrete surface. Seal cracks, crevices and potholes, and level out large protrusions.
• Clean from oil and grease stains and other contaminants.
• Careful alignment may not be necessary.
• Install a joist system on which the floor will rest. Secure with self-tapping screws and dowels or nails from a construction gun.
• Wet the concrete so that the foam adheres better.

Spraying polyurethane foam between joists

• Spray insulation for the concrete floor. The volume of foam when hardened increases by 5-10%. This needs to be taken into account.
• Wait until the foam dries completely.
• If the floor will not be laid immediately, cover the foam layer with light-protective material.

Other methods of thermal insulation of the floor are also used, such as filling with expanded clay followed by installation of a cement screed. This method also does not require careful leveling of the floor. If you add a sufficient amount of special polymer additives to the cement mortar, the screed itself will acquire thermal insulating properties.

Before you start

For thermal insulation work in most cases (except for sprayed coatings), only the usual set of construction tools is required, first of all:

• circular saw or jigsaw;
• screwdriver;
• roulette;
• corner;
• level;
• construction knife.

Almost all floor insulation work can be done alone. But with an assistant, the time will be significantly reduced, especially if the screed is done.

The need to screed the insulation arises in the following cases:

• Warm floor.
• Floors on the ground or on an insulated balcony or loggia.
• Significant thickness of the screed when leveling the floor in an apartment to one level.
• The need for additional sound insulation.

They began to make (massively) such a screed relatively recently. Therefore, there is a lot of fantasies and speculation - the technology has not been fully developed.

Not enough time has passed for error information to accumulate.

Which insulation is better?

Taking into account all the expanded clay and vermiculite bedding, as well as various additives to the solution, extruded polystyrene foam is the most popular insulation material. Its strength is beyond any doubt. It would be possible to stop at this option, but its price forces us to look for alternatives.

Laying the other two insulation materials (stone wool and ordinary polystyrene foam) on the floor under the screed raises concerns among many. This comes from ignorance of the varieties (brands) of these materials. Crumpled pieces of foam underfoot and mineral wool in rolls intuitively suggest that under a layer of mortar they will look even worse. If you clearly see the strength of the insulation intended for this purpose, then doubts disappear. The durability is impressive. This is more than enough for a screed in an apartment:

The second panel (crushed by a wheel) is filled with low-density mineral wool, which is used as a thermal insulation layer in facade systems. Not to be confused with stone wool samples intended for floating screed. You need to know, albeit superficially, the technological characteristics of the materials for laying under the screed and the one you have chosen. This is so that later, you don’t have to look for the reason why the screed bends.

Every brand that produces thermal insulation has this type of insulation. Also, it can be included in the name as a soundproofing material for the floor, under the screed:

• So Thermolife has slabs “TL Pol” and “TL Pol-S”.
• TechnoNIKOL has three types of such slabs: “Technoflor soil”, “Technoflor standard” and “Technoflor prof”. Each has its own purpose, characteristics and cost.
• ROCKWOOL has slabs “FLOOR BUTTS”, “STEPROCK ND”, “STEPROCK HD”.
• PAROC has a plate “PAROC SSB 1” and “PAROC SSB 4”.

All of these products have high density. From 110 kg/m³ (PAROC SSB 1) to 160 kg/m³ (Stroprock). Another indicator is compressive strength at 10% deformation. This value varies, from 20 to 40 kPa (PAROC SSB 4).

If we compare the cost of replacing (on large layers) cement screed with insulation, we get approximately the following price ratio per standard cubic meter of material:

APPROXIMATE PRICE RATIO.

Replacing a partial layer of DSP screed (2) with a sheet of extruded polystyrene foam (4) will have almost no effect on costs. Or perhaps a slight increase in price. But taking into account all the factors - delivery, labor costs for lifting and laying, weight for covering, insulation - the extruder wins by a small margin.

Savings are possible only by using ordinary polystyrene foam (1). With basalt wool (3) it is impossible to say for sure. Significant price range.

Calculations are approximate and depend on the quality of the material, the delivery area, and the characteristics of the work in the given area.

The thickness of the insulation screed and whether mesh is needed.

According to DIN (EU) construction standards, the thickness of the screed on the separating layer (in our case, insulation) must be at least 35 mm.

In all KNAUF designs this requirement is met. And reinforcing mesh is not provided as a prerequisite:

Only the lack of reinforcement raises concerns.

But if you look at the example of a screed using an extruder (UZIN company - UK), you can accept that this is possible:

What details can be noted:

• The solution is thick and wet. It does not look like a semi-dry screed solution. After leveling, the mixture squeezed water onto the surface. This is the ideal moisture content of the screed solution. Such a screed does not have the disadvantages of a semi-dry screed, when a loose structure is formed at the base. At the same time, it does not crack, as often happens with regular, wet ones.
• The sand is coarse, which promotes rapid shrinkage and squeezing moisture onto the surface.
• Perhaps they use additives (plasticizers) - the water that is added to the mixer is cloudy and not of a natural color.
• The base is made of extruded polystyrene foam.

But such conditions cannot always be maintained. Practice shows different results and therefore, there is a different opinion:

There is also a peculiarity in how to lay the reinforcing mesh. You can do it like here:

If the mesh does not overlap, cracks appear along the joint. The screed in such cases does not work in one piece.

This may not have any effect on the installation of laminate or linoleum. And perhaps it will somehow appear when laying ceramic tiles (the grout will crumble in individual seams). But this is guesswork. If you record (photo, video) such changes on the tiles after laying the mesh in the screed without overlap, then you can draw conclusions.

Laying insulation under the screed.

With the installation of insulation, a lot of fantasies also arise. Do I need to attach it to the base? And what to fasten it with? Many people think it’s better to fix it - it won’t get worse. And they are attached depending on the wealth of imagination: with glue, with polyurethane foam with plastic dowels, or simply with sand or crushed stone.

An interesting solution from KNAUF on this topic. Sheets of foam plastic are laid on a bedding of expanded clay and expanded clay sand. Backfill is a kind of invention by KNAUF and is called “Fill for prefabricated floors”.

The main thing you need to pay attention to in this process is preparing the base from bulk material using an aluminum rule. The length of the tool and the presence of at least some level on it allow you to get a good, even plane. This is necessary so that thin foam plastic sheets do not break, and durable EPS sheets do not sway:

The backfill can be replaced with sand, or even better, DSP. A mixture with cement is better because it will draw moisture out of the screed and harden. Well, just in case. The thickness of the leveling bedding can be minimal, within a centimeter. Careful preparation of the base allows you to lay the slabs (with rubbing) without voids. Then it becomes possible to make a screed using EPS without reinforcement.

Film for floor screed.

There is also confusion with film. Is it needed and where, on the insulation or under the insulation.

If we look at the working drawings of floating screeds from various manufacturers, the separating layer of film is placed only on top of the mineral wool slabs. Some call it a vapor barrier, some call it a film to protect the insulation from leakage of the solution.

And polystyrene foam (KNAUF recommendations) is covered with Schrenzlage lining paper. This is kraft paper coated on both sides with film. It is not a waterproofing or vapor barrier and is installed under a monolithic self-leveling floor in accordance with DIN 18560-2.

Similar recommendations for protecting foam plastic from cement mortar can be seen in some sources. The reason is that the alkaline environment destroys it. How then to deal with the insulation of all facades? When is a cement-based mixture applied to the exposed surface of polystyrene foam?

One more detail. KNAUF does not recommend the use of film due to the formation of wrinkles. Perhaps this is a marketing ploy - “nothing has been invented better than our lining paper.” But the last video (at the end of the article), where folds appear on the plastic mesh when pouring the Weber-Vetonit mixture, is thought-provoking.

Similar solutions for sound insulation from TechnoNIKOL and Ceresite:

What can be summed up:

• Ceresit allows screeding on mineral wool without reinforcement, but using its own mixture “Ceresite CN 175”. At the same time, the thickness of the screed (judging from the video) is solid - the maximum allowable for this mixture is 60 mm.
• KNAUF has a similar solution.
• Weber-Vetonit has a similar soundproofing floor design. Instead of film - geotextiles. The thickness of the self-leveling screed “Weber-Vetonit 4310” is 15 – 25 mm, “Weber-Vetonit 4350” 25 – 30 mm. Additionally, reinforcement is provided with WEBER R108 fiberglass mesh.