How to make the base of the floors under the screed from expanded polystyrene

Recommendation points

• Characteristics of extruded polystyrene foam
• Preparation of floors for screed from extruded polystyrene foam
• An approximate calculation of the cost of production of work for a room of 40 m2
• Expanded polystyrene or expanded clay

When repairing floors in residential premises or when entering a new apartment with a rough finish, many people have a dilemma – how to prepare for a clean floor. With modern building materials, floors can be laid directly on the concrete base. But in some cases it is necessary to carry out preparatory work..

These jobs include:

• soundproofing the floor – relevant in prefabricated panel houses of small apartments or townhouses;
• floor insulation – the first floor of any house, under the slabs of which there are basements or technical rooms;
• waterproofing the floor – in rooms exposed to a humid environment.

For all these types of work, you can use extruded polystyrene foam as the base of the floors under the screed – the most common type of construction work.

Characteristics of extruded polystyrene foam

Polyterol foam is a building material produced industrially using the most advanced equipment. It is a board based on polystyrene and styrene copolymers. Internal granules of expanded polystyrene, depending on the purpose, are filled with natural or carbon dioxide under pressure. Expanded polystyrene, like many building materials, differs by brands:

1. Grade 31 (31C) is intended for work on a structure that does not bear loads – heat insulation of floors in non-residential premises, foundations, inversion roofs. Has minor fire resistance requirements.
2. Grade 35 differs from the above-described grade in that in the manufacture of expanded polystyrene, fire retardants are added to the bulk, which significantly increase the fire resistance of the building material. Used as an insulating material in residential and industrial construction.
3. Grade 45 – has high compressive strength and is intended for use on an industrial scale – the construction of roads, railways, runways, is used for special construction work.

It is recommended to use extruded polystyrene foam grade 35 (C35) for the production of screed floors. Standard dimensions of expanded polystyrene sheet 1250x600x20, thickness: 30, 40, 50, 60, 80, 100 mm. The package contains 0.288 m³ (9 m²) building material.

Characteristics of extruded polystyrene foam:

• compressive strength (deformation 10%) – more than 0.16 MPa;
• density – 25–35 kg / m³;
• bending strength – from 0.25 MPa
• water absorption – 2% of the total volume (for 24 hours);
• thermal conductivity – less than 0.037 W / m²° C.

When buying extruded polystyrene foam M 35 (35C), you should pay attention to the certificate of quality or conformity, which must be attached to the building material. It should indicate that expanded polystyrene, as a building material, is intended for interior work in residential premises (!).

In addition, the accompanying document is the conclusion of the SES, which indicates that the material does not pose a threat to human health. If expanded polystyrene meets all the requirements, then it:

• not exposed to the negative effects of ultraviolet radiation;
• chemically inert to the effects of various aggressive environments;
• not toxic;
• does not emit harmful substances when exposed to an open flame;
• has a low flammability (up to +500 ° C). When the heating source is removed, it fades out after 1–3 seconds;
• is a durable building material.

Preparation of floors for screed from extruded polystyrene foam

It is worth paying attention once again to the fact that the laying of expanded polystyrene is a preparation for a flooded floor or a base for installing a clean floor. It is recommended to lay it after the laying of electrical cables and communications.

Before starting the work, you should calculate the amount of material required – the standard sizes and volume of polystyrene foam packaging are indicated above. The volume of building material is taken with a margin, usually 5-10%. With initial construction preparation, this work can be done independently.

The base on which the expanded polystyrene will be laid is dedusted, the baseboards (if any) are dismantled. Next, you need to make waterproofing.

Be sure to waterproof the corners of joining the walls with the floor, along the entire length.

The waterproofing strip is made at least 20 cm wide (from the corner), 10-15 cm high above the level of the finished floor. When technologically necessary, waterproofing is applied to the entire base area.

Waterproofing can be penetrating or coating – this is not important, the main thing is that it meets the requirements for the surface on which it is applied. That is, if the waterproofing is designed to work with a concrete base, then it should be taken for this type of work. Apply the waterproofing compound with a brush or roller.

After the waterproofing has been applied, allow time for it to dry. Time can range from several hours to a day (this is indicated on the package).

After waterproofing works, polystyrene foam is laid. The material is laid in the direction from the corner of the room to the door. Cutting is done with a construction knife with replaceable blades. Expanded polystyrene sheets are stacked end-to-end, with a maximum gap of 2-3 mm. If the gap is larger, then it is filled with sealant or mastic using a construction gun..

If communications and electrical cables are laid along the floor, polystyrene foam is cut in such a way that communications pass inside the technological channels.

It is important to know – electrical cables should be enclosed in metal or plastic boxes with grounding or corrugation. Water pipes are insulated with any type of pipe insulation.

The communications in the channels should be located so that there is a distance of 5–7 cm to the edge of the expanded polystyrene. The channel can be filled with shavings or small pieces of the same expanded polystyrene.

When laying the sheets on a wooden base, they can be screwed to the floor with ordinary screws to fix them. Or with a dowel – anchor with pre-drilling if the base is concrete.

The sheets are fastened “without fanaticism”, with a penetration of expanded polystyrene into the body by 2–3 mm. You can also use an adhesive base – but this will take additional time to dry..

Extruded polystyrene foam, for a number of reasons, can be laid in two or more layers. Then the cutting and laying of the sheet material is carried out in such a way that the joint seams are not one above the other. Simply put – a dressing is performed, that is, the joint seams of the upper carpet run at a distance of at least 20-30 cm relative to the joint seams of the laid lower sheets.

After the expanded polystyrene is laid over the entire surface, the technological channels are reinforced. For this work, you can use a steel mesh with a mesh size of 100×100 mm. The steel mesh is cut into strips, taking into account that its edges completely cover the technological channel and go into the general foam polystyrene carpet at 7-15 cm from the edge of the channel. At the edges, the mesh can be fixed with simple screws or nails..

After laying the expanded polystyrene, work is done on the floor.

Extruded polystyrene foam is an excellent base for flooded floors of any type or as an element of a wooden floor. When installing a wooden floor, polystyrene foam is placed inside the crate between the logs, according to the same principle as described above.

An approximate calculation of the cost of production of work for a room of 40 m²

To calculate the cost of the work, we take the laying of expanded polystyrene in 2 layers, with a sheet size of 1250x600x30 mm.

The volume of the required building material is (taking into account 10% of the stock) – 9 packs, at a price of 1200 rubles / pack. = 10800 rub.

Lubricating waterproofing (bag of dry mix 40-50 kg, at a consumption of 2 kg / m²) – 1000 rubles.

Consumables – construction knives, hardware, steel mesh, etc. – 2000 rubles.

Delivery of material – 1000 rubles.

Total: 14800 rubles.

Labor costs when working 2 people – 1 shift, 16 people / hour.

A screed performed on a base made of expanded polystyrene, with a thickness of 7-10 cm – 450 rubles / m² = 18000 rub.

That is, a rough floor with excellent characteristics costs 32 800 rubles.

Expanded polystyrene or expanded clay

Expanded clay is an alternative to the base for flooded floors. The technology of flooring, using expanded clay is a little simpler – it is spread in an even layer (with or without a slope) of the required thickness, after which it is reinforced with a mesh – but over the entire area. After reinforcement, start pouring the floors.

So, comparing extruded polystyrene foam and expanded clay, you can identify a number of advantages of one building material over another.

Pros of expanded polystyrene:

• reliable fixation to the base;
• no dust during work;
• excellent thermal insulation and waterproofing characteristics;
• works with any finishing building materials.

Cons of expanded polystyrene:

• collapses when exposed to an open flame;
• corroded by certain substances, such as gasoline.

Advantages of expanded clay:

• fire resistant material;
• when laying, it does not require preliminary leveling of the base;
• not exposed to the destructive actions of aggressive environments;
• has excellent thermal insulation.

Cons of expanded clay:

• labor intensity of transportation to the place of laying;
• when wet, it retains moisture in its mass;
• requires constant alignment, as it is a movable material;
• a lot of dust is generated during installation;
• with a large layer may shrink.

What material to use for the installation of the base under the flooded floor is decided independently or according to design solutions.