Waterproofing a bathroom under tiles

Recommendation points

• Floor waterproofing
• Types of materials
• Preparatory stage
• Roll-up waterproofing
• Waterproofing with coating materials
• Features of waterproofing floor on a wooden floor
• Wall waterproofing

Bathroom waterproofing is aimed at protecting against water leaks. It is needed not only by the premises located on the floor below, but also by the materials of the floors and walls. The use of ceramic tiles as a moisture-resistant finishing material does not exempt from the need for this stage.

Floor waterproofing

Types of materials

Waterproofing materials are classified as follows:

• painting;
• coating;
• roll;
• leafy;
• impregnating;
• injectable.

Each group has its own specifics.

Injection waterproofing is a repair compound for the restoration of waterproofing of basement walls, basements and lower floors.

Impregnating waterproofing has practically the same principle of operation as injection – penetration of the composition through capillaries and microcracks into the structure of the base material, crystallization and “blockage of channels” through which water can penetrate deep into the materials.

Sheet waterproofing is a polymer or rubber sheet held together by waterproof welded, brazed or adhesive seams.

Of the first three groups, roll materials impregnated with modified bitumen are considered the most reliable in conditions of pressure water pressure. They are used in the most difficult places: floors, foundation walls, roofing. That is, where water can exert pressure on the enclosing structure. Bathroom floors are no exception. But even in this case, it is more correct to talk about the integrated use of several types of materials, when the main “barrier” is created due to roll waterproofing, and painting, impregnating and sheet perform an auxiliary, but no less important role.

Note! Roll materials are best used on a bitumen basis. Polymer films do not have sufficient reliability and durability. And although they still demonstrate quite high resistance when exposed to an aggressive alkaline environment of wet concrete, it is much better in glass cloth or textile cloth with bitumen impregnation.

Preparatory stage

In principle, the very preparation of the base for arranging waterproofing under the tiles has the same algorithm as for ordinary flooring. The main task of preparation is that the surface should be free of serious defects and relatively flat.

If a major overhaul or reconstruction is being carried out, then the old floor covering must be removed, the screed (or overlap) must be inspected and, if necessary, the base must be repaired:

• clean from debris and dust;
• prime the joints of the slabs and crevices;
• repair them with repair compounds.

At the same stage, you need to pay attention to the water supply and sewer communications that pass through the floor. It is quite possible that the old coating in the floor slab will have to be removed (or expanded) and the inlet slots covered with a new solution based on a waterproofing compound.

As a result, the surface of the base before applying the waterproofing layer must be flat – a height difference of no more than 2 mm and the complete absence of “sharp” edges and protrusions are allowed.

You can finish the preparatory work by applying a deep penetration primer with a hydrophobic effect – to some extent, it acts on the base as an impregnating waterproofing. It should be borne in mind that the waterproofing of the floor must have access to the walls (up to 20 cm), and they must also be prepared.

Roll-up waterproofing

According to the method of application, roll waterproofing is also called gluing.

In order for the base to have good adhesion, a layer of bituminous primer is applied to it. This is especially true if a sheet of rolled waterproofing is fixed with a blowtorch or a construction hair dryer, melting bitumen on its inner surface.

You can use mastic instead of a primer, which differs only in concentration, but for domestic conditions this is somewhat redundant.

The primer is used to treat not only the surface of the base, but also the walls around the perimeter of the bathroom to a height of up to 20 cm, as well as the risers of the water supply and sewage systems.

Rolled waterproofing is glued in strips, with an overlap between adjacent sheets of about 15 cm.In addition to traditional materials fused to the surface with a blowtorch, there are self-adhesive types of rolled waterproofing, which are much easier and more convenient to install, especially for non-professionals.

Seams between overlapped strips are treated with mastic.

Along the perimeter of the room, the sheets should extend onto the wall to a height of 15-20 cm.

When passing through the pipe strip, a hole is cut in the sheet with a smaller diameter than the pipe itself. Small notches are made inside the hole and the edge is bent outward so that it covers the pipe, a narrow strip of rolled material is soldered on top, and then all seams are treated with the “cuff” with mastic.

Waterproofing with coating materials

In this case, as in the previous version, the main task is to create a kind of waterproof “trough” on the floor (with the same side height 15–20 cm).

The method is much easier to apply, since such waterproofing refers to a seamless look, and the requirements for the quality of the base surface are not so stringent.

They use bitumen, bitumen-polymer, cement-polymer mastics, which are applied to the floor (with access to the walls) in two or three layers.

The disadvantage is the higher cost of materials.

Features of waterproofing floor on a wooden floor

When laying tiles on a wooden base, it is important to consider the characteristics of two different materials – wood and ceramics. They react differently to changes in humidity and temperature, so the base (sub-floor) is arranged in a floating way:

• sheets of moisture-resistant plywood cut into pieces are screwed to the wooden floors;
• plywood is stacked with a gap between the sheets of 3-5 mm;
• a damper gap is left around the perimeter of the room, into which an elastic tape is placed;
• the seams between the plywood sheets are closed with a sealant, and around the perimeter of the room, the corner joints are pasted over with a protective moisture-resistant tape;
• apply two or three layers of coating waterproofing (with access to the walls).

In principle, tiles can already be laid on such a base, but for greater reliability (and a more even distribution of the load over large areas), you can additionally fill in a small layer (up to 3 cm) of a leveling polymer-cement screed (reinforced with fiberglass mesh or microfiber).

Wall waterproofing

Waterproofing the walls of the bathroom is necessary in those areas where there is a possibility of direct ingress of water – bath, shower and washbasin.

In these places, coating and impregnating materials based on polymer-cement compositions have proven themselves best..

Apply waterproofing compounds to the prepared wall surface, which must be strong, even and clean. Before applying the composition, these zones must be treated with a primer with a hydrophobic effect..

After tiling and installing plumbing equipment, the junction to the walls must be treated with a sealant.