How to lay tiles on a wooden floor

Recommendation points

• What are the difficulties of laying tiles on a wooden base
• The main ways to solve the problem
• Reinforcement with sheet materials
• Prep screed method
• Floating floor technology
• Laying tiles

The arrangement of the wooden floor throughout the floor plan looks very tempting: the covering is warm, it naturally regulates humidity and has a chic look. But do not rush to rejoice: difficulties await you in laying the coating in the kitchen and in the bathroom, where tiles are traditionally used..

What are the difficulties of laying tiles on a wooden base

Ceramic tiles are hard coatings that do not experience shrinkage and linear expansion during operation. The general principle of combining building and finishing materials is to ensure the greatest possible degree of their homogeneity. Thus, the behavior and physical and mechanical properties of the tile must be inherited by the base on which it is laid..

Wood does not meet these requirements. With changes in temperature and humidity, the tree is prone to shrinkage – a change in linear dimensions and shape. Even tightly knit massive boards are able to “play” within 1.5–2 mm, which is absolutely unacceptable for tiling. Nevertheless, laying tiles on a wooden floor is possible, for this it is required to protect the wood from the influence of the environment in all possible ways and create a kind of damping layer that can absorb the vibrations of the base and provide a rigid fixed plane for laying the tiles.

Usually, the need for laying tiles on a wooden floor is avoided by all means. This is achieved by constructing a part of the floor using a different technology, for example, by pouring a screed over the ground. However, the combination of floor systems causes difficulties in making connections between them, and the pace of construction work slows down. Hence, an important conclusion: to prepare a wooden floor for tiles should only be done if it is justified from a practical and economic point of view..

The main ways to solve the problem

There are three fairly well-developed and studied technologies for arranging a tile base on a wooden floor. All of them have a significant drawback: as a result, the coverage level is higher than in other rooms, while in reality the opposite effect is required. A tiled floor is usually arranged in kitchens or in bathrooms, in the latter case, building codes require an understatement of the finished floor by 50 mm. This feature must be taken into account in advance, using larger logs when installing the supporting system in other rooms, and in rooms under tiles – a rough flooring of boards of minimum thickness.

The first way to arrange a base for a tile is to fill a preparatory screed. It is especially good in that it allows for full floor heating. From the point of view of the service life, the screed demonstrates itself from the best side, its service life is 20–35 years. The main problem is a rather complex technology of the device and the need to perform “wet” construction work.

The other two methods are very similar. The first one is applicable to relatively stable wooden floors and consists in laying several layers of sheet materials on top of the rough plank flooring, which are not subject to shrinkage and warping. OSB, moisture-resistant plywood and chipboard can be used as such materials, while raising the floor mark is the minimum possible. The third option implies the presence of a layer of loose material of arbitrary thickness between the wooden floor and the sheathing. This is required in cases where the mobility of the rough flooring is extremely pronounced and there are no other ways to compensate for it. The disadvantage of the last two methods is the practical impossibility of arranging floor heating and a large material consumption.

Reinforcement with sheet materials

Large-format sheet materials help to reliably tighten the boardwalk, providing the necessary rigidity and immobility of the base. The best result is achieved by laying two or even better three layers of low thickness. Moisture-resistant birch plywood, class 3 and 4 OSB, chipboard and various combinations of these materials are well suited for such applications. It is possible to achieve high-quality compensation of movements in the base by using magnesite glass plates in the lower layer. The total thickness of all layers should not be less than 25 mm.

All layers of the flooring must be securely pulled together. For this, ordinary black self-tapping screws are used, which are screwed in without pre-drilling. It is optimal if the thread on the fastener is made with a “neck” of 15–20 mm. The first layer must be fixed in such a way that the sheets are drawn to each board along the edge and at a distance of 25–30 cm in the central part. All subsequent layers are attracted to the previous ones with a step of 150-200 mm along the edges and about 300-400 mm in the middle part. When laying sheets between them, you need to leave a gap for thermal expansion of the order of 3-5 mm.

Prep screed method

The screed is poured to immobilize the surface due to the weight and stiffness of the concrete mass. Previously, it will not be superfluous to assess (at least by eye) the limiting degree of deformation of the plank floor. It will depend both on the step and section of the lag, and on the thickness and quality of the boards to be laid. According to the data obtained, the maximum permissible screed deflection should be indicated, it can be calculated using the method of calculating the deformation of a concrete slab on an elastic foundation.

Typically, vibrations of a well-laid sub floor do not exceed 3-5 mm / m and 8-10 mm in general. To effectively counteract such curvatures, either a sufficiently thick layer of screed is required (35–40 mm, the optimal thickness for a warm floor), or the introduction of reinforcement – a steel welded mesh of 4 mm wire with a cell of 150×150 mm or finer.

When installing a screed on a wooden floor, the first step is reliable waterproofing. First, along the perimeter of the room, a compensating tape made of expanded polyethylene with a thickness of 5–6 mm is shot against the walls. If you plan to include heating elements in the screed, expanded polystyrene plates are glued to the boards. Further, the entire floor area is covered with a polyethylene film with a thickness of 250 microns, the edges are folded onto the walls with an overlap of 10-15 cm, gently bending in the corners. It is optimal if a solid canvas is laid over the entire area, otherwise the film will have to be welded or glued with tape on both sides with an overlap of 25-30 cm. If necessary, you can shoot the film to the floor, but each bracket must be covered with a piece of adhesive tape.

If the decision is made to use reinforcement, it is placed on the spacers. The perception of bending loads will be optimal when the reinforcement mesh is placed in the bottom row with a minimum protective layer thickness, that is, 5–7 mm. After laying out the reinforcement with a step of 1.3–1.5 meters, beacons are installed along the long side of the room, leveling them at the desired zero mark of the finished floor minus the thickness of the tile and the glue seam. Lighthouses should be fixed on lumps of the same grout that will be used for pouring. To accelerate the setting, you can add up to 15–20% alabaster to the mixture. After hardening and checking the correct installation of the beacons, a screed is poured, the mixture is drawn by the rule along the beacons. The latter are removed on days 2-3 of exposure, the furrows are sealed with a solution of the used brand.

Floating floor technology

The essence of the third method is the creation of a damping layer from a bulk incompressible material, followed by a hard coating. The latter can be both sheet flooring, including from MGL and GVL, and a reinforced sand-concrete screed. The method has an additional advantage – a sufficiently high degree of noise isolation.

The bulk layer should not be made too thick, 4–5 cm is enough. The filler can be perlite, expanded clay of 4–6 mm fraction or granulated foam glass. Lighter filler means less load on the subfloor and, accordingly, higher bar of permissible operating load on the finished floor. The floor filler must be dry and treated with insecticidal and bactericidal agents, it is possible to add slaked lime in an amount of 3-5% by weight.

The filling is carried out in one layer, which is aligned with the adjustable beacons and compacted well. Above the leveled embankment must be covered with plastic wrap and, after leveling is completed, move only along ladders made of rigid sheet material.

The choice of a floating floor base is relatively free. A screed with sand concrete of class B22.5 at least 30–35 mm thick with polymer reinforcement will provide an operating load of about 150 kg / m². When using sheet materials, the hardness of the floor is determined by their passport data and the number of layers. The latter, by the way, should be at least two, laid with bandaging joints at least 30-35 cm.

Laying tiles

The final stage of the flooring is no less important than all the previous ones. For the best result and durability of the tile, two additions to the standard installation technology can be recommended. Before proceeding with the cladding, it is necessary to ensure high-quality adhesion of the adhesive to the base, for which the floor is opened several times with an adhesive primer. The composition is selected according to the purpose for the type of material used.

The first important addition is wiping the floor with an adhesive mixture and embedding a fiberglass mesh into it for facade work. It will give the surface additional rigidity and eliminate the movement of the adhesive layer..

The second nuance can be called mandatory: you should use special types of tile adhesive. A good option would be elastic Ceresit CM 16 or CM 17 for critical substrates.