Wetrooms – Tanking Systems

Jason Brunt, UK Ceramic Product Manager at Mapei UK

Years ago the idea of having a wetroom was a luxury most did not believe they could afford.
Development of waterproofing and ceramic products across the sector means that constructing a wetroom is now a feasible and popular project.

What is a wet room?
The basic idea of a wetroom, is of a room constructed without the use of a conventional shower tray and screen. Why you may ask? Depending on the space allowed, removing the tray can give more room to use the shower, as well as reducing the step area meaning easier access, with the floor construction angled to allow water drainage.

The easiest way to get the correct run to the drain is to utilise a preformed base. These can be fitted to the current floor height on timber bases by adding timber supports to the joists, and are commonly fixed in place using flexible cementitious adhesive. They can be fitted in a way so that the surface finishes at the same height as the rest of the surrounding floor.

What is important when considering a wetroom?

It may seem obvious, but ensuring all of the specified materials work together in unison to ensure that water does not escape or cause damage, is the primary concern for installers. It makes no difference whether the wetroom is on the ground floor, 1st or the 40th floor, water must not travel anywhere we do not want it to.

The British standard 5385 part 4 covers how to locate a “special area” such as a wetroom. Substrates used for the construction of the wetroom need to be water resistant, however being waterproof isn’t a necessity as a tanking membrane can be applied to waterproof the area.

Water resistant materials will allow water to pass through but will not damage or degrade. Water proof means that water cannot penetrate. Therefore even water resistant materials still require some form of waterproofing.


What does “tanking” mean?
“Tanking” is quite a widely used term and often relates to the water proofing of basements against water infiltration from an external source. These types of tanking can be externally applied to prevent positive water pressure as well as internally applied against negative water pressure. In the case of a wet room we are trying to waterproof a substrate while redirecting the flow of water to an escape drain.

The type of tanking used can be a single part paint on system, a two-part cementitious system, or a sheet membrane system.

What is in a tanking system and how is it applied?
A single-part paint on system forms a waterproof coating once it has dried. Mapei’s Mapegum WPS is a standard setting coating, whereas if a quick-setting version is required, Mapelastic Aquadefense is the ideal product. These systems can be applied to moisture resistant boards on both wall and floor areas.

The joints at the internal corners, where the wall meets the floors and any joints in the boards should be reinforced with Mapeband PE120 tape. Tanking paint is adequate on a solid surface, however where differential movements take place, if you were to  simply paint this joint, splitting in the coating would occur. Mapei tapes contain a flexible rubber strip which will allow for the movements between the substrates.

A single part paint on system can also be installed with a fleece membrane such as the Mapetex SEL. The fleece will benefit the water proof coating by providing a reinforcing layer between the coats. This layer enhances the crack bridging ability of the water proofing and can reduce the risk of any splitting in the water proof coating should there be large amounts of lateral movement.

A two-part cementitious system can also come in a standard or quicker setting formula. Mapei produces Mapelastic smart and fast drying Mapelastic Turbo; two components are mixed together and applied with a trowel, brush or roller. Again the joints at the substrate changes where wall meets floor and will require the inclusion of a reinforcing tape. When using cementitious products an alkaline resistant tape such as Mapeband should be used. The tape contains a rubber fillet and is fleece lined to allow the bonding when applied between coats of the waterproof tanking to form a water tight seal at the joint. As per the single part system, Mapetex SEL can be used to reinforce the water proofing layer; for heavy duty areas such as swimming pools, Mapenet 150 alkaline mesh net can be used, this is placed in the first coating of the water proofing before being smoothed over with the second coat.

Sheet membrane systems such as Mapei Mapeguard WP200 are made of a soft polyethylene and at less than 1mm in thickness, provide an excellent waterproof barrier. Mapeguard WP200 forms part of a system when used for waterproofing, with anti-fracture properties already encompassed in the fleece material of the Mapeguard WP200 reducing the need for an additional product. Whilst the material is water impermeable, joints will still require taping to form the seal. Components required for the Mapeguard waterproofing system include the WP200 sheet membrane, the standard joint tape Mapeguard ST, the IC and EC (internal and external corners) and pipe gaskets, which come in three sizes. The Mapeguard WP adhesive is a fully water proof adhesive which is used to fully bond the tape, IC’s, EC’s and gaskets to the Mapeguard WP200. Finally, Mapeflex MS45 sealant for drain outlets ensures a fully watertight seal.

Applying the Mapeguard WP200 can be done with a thin bed of a C2 classification adhesive depending on the substrate. In the case of a moisture resistant board on the wall and a plywood floor for example the Mapei Keraquick S1 adhesive can be used on wall and floor. The quicker the set time on the adhesive, the quicker the coverings may be applied after.


Tiling the wetroom
Once the tanking has been completed for the wetroom, tiles can be applied.

One of the main considerations when specifying the tile for the immediate and surrounding wet area, is the slip resistance of the tile – it is important that the R rating is R10 – R13.

A mosaic tile is the easiest type of tile to install on the wetroom base as the mesh backing and the size of the tesserae allows for the tiles to be easily laid with no need for cutting. Mosaic finishes have more grout joints, thus simultaneously improve the slip resistance of the floor.

Fixing tiles in the wetroom can be done using most cementitious adhesives depending on the tile size and substrate type, as the adhesives themselves are water resistant.

The next choice to make is the grout
The minimum classification for grout used in a wetroom environment is ideally CG2WA. This is an improved formulation cementitious grout, being both water and abrasion resistant. Mapei’s Ultracolor Plus grout has a range of over 30 colours giving the client an excellent choice to either match or contrast with the chosen tile colour, with an ideal grout for a wetroom being epoxy based. The main reason for the choice of the epoxy is the impermeability and the inherent benefits this brings.

Water resistance means the water will pass through the material, but not damage or degrade. A cementitious grout therefore will allow water to pass through, but what we have to consider is what the water is moving; avoiding the transferal of soaps, shampoos and waste water into the grout joint is paramount. Adhering to the CG2WA classification means that fissures in the grout are closed – and in the case of Mapei’s Ultracolor Plus high levels of polymers are included, giving a higher rate of water resistance. The tightness of the surface can reduce the amount and size of the particles entering the grout which may lead to staining. A CG1 grout can have high rates of absorption and thus a higher contamination level than a  CG2 classified grout. Once the contaminants get in to the grout joint there can be a risk of mould growth on contaminants lodged within the grout. The application of an impervious epoxy grout such as Mapei’s Kerapoxy Design means that there is no risk of staining or mould growth within the grout joint.

In short..
An attractive wetroom environment is easily achievable and is also easy to maintain. Key facts to consider for your wetroom include:

1.    Ensuring a suitable substrate
2.    Making sure that the levels of water output and the falls in the wetroom area are compatible
3.    The area needs to be fully water tight and carefully prepared
4.    Tiles need to be suitable for the wet area for safety reasons
5.    Specifying the correct adhesive and grout is essential for ease of application and maintenance

Mapei UK Ltd
Head office, Mapei House Steel Park Road, Halesowen, West Midlands B62 8HD
0121 508 6970

Specification Centre, 6 Great Sutton Street, Clerkenwell, London EC1V 0BX
020 302 9610