Builders wet rooms Q & A

Questions commonly asked by Builders about wet rooms

Builders are probably the most  consistent and frequent customers of On The Level, so we thought we’d share some of the most common questions asked by them in relation to installing wet rooms.

If you have a wet room question you think should be featured here, call us on 0845 346 4753 or email us at

What’s the importance of making sure the gradient in the floor is sufficient?


It’s so important to make sure the gradient in the floor is large enough to capture all the water that sprays from the shower. If the former and gradient area are too small and the area is not enclosed using a glass screen, water will sit on the flat floor area outside the shower zone and flow away from the gully. It’s important to use a former as large as possible to prevent this from happening.

What tile size is best for a wet room?


The tile size really does depend on what the client wants. There is a general consensus that mosaic tiles are easier to fit when installing a square grating type system and large format tiles are predominately preferred in conjunction with a linear channel style wet room. The tile thickness can range from anything between 3mm porcelain sheets up to 40mm marble slabs with standard 10-12mm tiles in between. To give you an idea, the visual to the left is not finished and shows a 30mm cast concrete slab installed. This really does provide a clear view of what can be achieved.

Is it absolutely necessary to tank a wet room?

Tanking is really only compulsory when the floor is being tiled. Tanking acts as a membrane which is installed before the tiling process takes place. It forms a seal, preventing any water penetrating through grout lines so there will be a secure barrier to prevent water from coming through the floor. A tanking membrane provides the client with the reassurance that their wet room will be 100% watertight. To the left, the picture demonstrates a fully tanked area prior to tiling installation. Tiles are installed directly over the tanking membrane. Underfloor can also be used in conjunction with the OTL tanking system. There is no tanking required when using a non- slip vinyl sheet flooring ( something similar to Altro Aquarius or Polyflor ). Vinyl sheets need to be installed by a specialist, as during the installation all seams are hot seam welded, which effectively simulates the vinyl sheet flooring becoming the tanking membrane. Underfloor heating should not be used when installing vinyl sheet flooring for wet rooms.


Tanking Video Preview