DIY: How to tank a wet room and prevent leaks from the get-go

Tanking is an essential step in installing any kind of shower. Here's how to do it right for leak-free showering bliss.

Tanking is a waterproof membrane between the tiles in a wet room (or indeed any wet area) and the underlying surfaces, which protects these substrates from water damage, damp and mould.

Tiles and mosaics offer a beautiful finish, however, they are often attached to walls and floors made of wood, plaster, plasterboard and other materials that are prone to water damage. Tiles are simply not waterproof enough to prevent moisture from getting through to these substrates. 

In addition, cementitious-type adhesives and grouts used to fix tiles are also porous. Over time, water will seep through the grout and adhesive to the underlying surfaces.

If the substrate is not protected, the tiles are compromised and will eventually come lose from the surface. The resulting damp is also likely to spread and cause damage to adjoining rooms, or in an upstairs bathroom it could seep through the floor, get into joists and create damp patches on the ceiling below. Any wet area (wet room, shower area or steam room, or any other location subject to frequent water contact) should be waterproofed before tiling.

The tanking membrane is flexible and allows some movement without the risk of leaking.

Wet room trays

Before a wet room can be tanked, a preformed tray (otherwise known as a wet room tray) with the correct gradient (1:40) needs to be installed. You will find wet room floor formers in various sizes at World of Tiles.

Unlike traditional showers, wet room trays don’t have a lip, sit flush with the floor and, therefore, pose less of a tripping hazard.

Drains

Wet rooms generally have a central, or an offset drain, but linear (or channel) drains, such as the Alcaplast range, are becoming increasingly popular.

Linear drains run parallel to one side of the wet room, and, as a result, overcome any problems related to the position of floor joists because the water can flow out from any one of the three outlets along the length of the drain.

How to tank a wet room

Tanking systems, such as the Arc Waterproof Tanking System, include a primer, tanking solution or paste and joint tape.

• Make sure the floors and walls of the wet room space are completely dust free and dry before you begin the tanking process.
• Paint the primer on the walls and floor that are going to be tanked using a paint brush or roller. Allow to dry.
• Use a brush to paint the tanking paste over all the horizontal and vertical joints, corners and outlets. Next, lay the joint tape over the lines of tanking paste and smooth it out to remove any air bubbles. Overlap the tape in the corners. Allow to dry completely.
• Next, apply the first coat of tanking paste over the entire wet room area including the joint tape. Allow to dry, and then apply a second coat. 
• Wait 24 hours for the tanking membrane to dry completely before you begin tiling.