Why correct product selection is crucial when designing a wetroom

Why correct product selection is crucial when designing a wetroom

November 2018

By David Wilson, Technical Services Manager at BAL.

When selecting products for use in areas such as bathrooms where showers and, of course, wetrooms are more prevalent, it is vital to make the correct choices early to avoid future problems and potentially costly failures.

Recent changes to BS 5385 Part 1: 2018 highlight the need for additional waterproof protection of water sensitive backgrounds for internal walls in wet areas, such as gypsum plaster and plasterboard.

Ensuring that water-sensitive or water-resistant backgrounds in your wetroom or shower installation are fully waterproof is perhaps one of the most important considerations.  This is because tiles, tile adhesive, and grout on their own will not protect against water ingress.

This is outlined in the British Standards where it states that: “The use of impervious grouts and adhesives is no substitute for a tanked installation.”

The effects of water damage are well known and documented.  Therefore, in line with the British Standards recommendations, we would always recommend incorporating a suitable waterproof tanking system onto non-waterproofed substrates prior to tiling wet areas.  The substrate surfaces are always to be prepared correctly with the application in mind and prior to the ceramic or natural stone tiles being fixed.

In wetrooms, it must always be ensured that consideration is given to the positioning of the shower head, the type of floor drain selected is adequate for the output, and the location of the shower does not create problems for water migration from the room.

Other major considerations include the weight of the tiling for the type of background selected, and the slip resistance of the tiles on the floor.

Waterproof tanking systems applied as a continuous membrane are ideal as they are specifically designed to stop water and prevent it from further ingress following it tracking through grout joints.  This is why it is important to specify waterproofing on both walls and floors in wet areas.

A tanking slurry, such as BAL Tank-it, can be specified to provide a waterproof background in typical installations involving tiles in wet areas i.e. showers, swimming pools etc. two-part product; BAL Tank-it has EN Classification under BS EN 14891.  This means it is suitable for swimming pools and external waterproofing including terraces, balconies and even fountains.  BAL Tank-It may also be used in internal areas for wetrooms and showers.

Surface inspection is essential
Before preparing any background always ensure that the surface is flat, clean, dry, sound, and free from barriers to adhesion.  All falls in floors should be designed to be between 1:35 and 1:80.

For example you may need you or your tiler to render solid uneven brickwork walls first with a product such as BAL Quickset Render, or correct floor levels using a floor levelling compound such as BAL Level Max, ensuring SR1 surface regularity (no greater than a 3mm gap under a 2m straight edge) as required by British Standards.  The waterproof membrane should also be capable of connecting with the floor drain selected. This should always be checked first.

With some waterproofing products it may be necessary to also prime the background first (although this is not always necessary with BAL Tank-it).

When selecting the right tile adhesive and tile grout for your wetroom, shower or bathroom, several factors need to be considered, including the substrate, tile size/type, and the environment.

Omitting primary waterproofing systems or selecting the wrong adhesive or grout, could lead to disastrous and unsightly consequences including cracking or de-bonding of your tiles.

This can result in remedial work, financial pain, intrusive repairs and on occasion recompense. Purely by specifying an adhesive or grout based on its classification alone does not always guarantee success – as other factors may make the selection invalid.

Selecting a suitable substrate
Firstly let’s look at the substrate or background.  Whether the tiles will be going onto plasterboard, tile-backer boards, tongue & groove floorboards, sand: cement screeds or even existing tiles; there can be a significant differences between adhesive selections.

For example, where floor coverings need to resist some limited movement or vibration, then a flexible possibly even a deformable adhesive and grout with suitable flexible properties should be selected. 

Polymer-modified adhesives and grouts have the addition of powdered polymers, pre-blended at the manufacturing stage or can be modified with a liquid polymer additive.  This further enhances the physical and mechanical properties of the product.

In a wet area, the adhesive and grout must be capable of being exposed to dry and wet conditions. It should also be able to withstand thermal fluctuations; particularly if the assembly includes underfloor heating.

Other environments require provision of tiles and tile fixing products which are capable of withstanding demanding conditions during service such as:-

  • Supporting heavy weights/loads in conjunction with the substrate tolerance.
  • Water and frost resistance.
  • Abrasion resistance (for grouts particularly for power showers or Jacuzzis)
  • Withstanding exposure to cleaning and maintenance chemicals.

Tile type and size also plays a significant factor in determining your adhesive and grout.  Ask yourself: “Are my chosen tiles porous?”  Are they glazed, fully vitrified, light-coloured/translucent or natural stone?  Is the material you are using vulnerable to water-staining?  Are you using large format or mosaic tiles and are they mesh-backed?  Are the tiles slip resistant?  This is crucial for planning a wet room for safe use.

One example, ready-mixed adhesives may be suitable for porous-bodied ceramic tiles, but for porcelain tiles a highly polymer-modified cementitious adhesive would be recommended.  Ready-mixed adhesives are also not suitable for floor tiling or for fixing tiles on walls where the tile is over 0.09 sq. metres in area.

Where light colours or translucent natural stone is to be installed; a rapid-setting and drying white cementitious adhesive - such as BAL Rapid-Flex One - is recommended to minimise any potential risks of water staining.  A pourable thick bed adhesive, such as BAL Pourable One may be required for floor tiling with large format tiling or uncalibrated natural materials.

The use of water sensitive agglomerate or water sensitive natural stone tiles or slabs in wetrooms is not recommended as they can be adversely affected with changes to moisture and thermal cycles.

There are additional factors which should be considered and more importantly are not covered by the tile adhesive classification.  Some of these include ease of use, coverage, colour, pot life, working or adjustment time, and cost.  As an example, in hot weather, a standard set adhesive should be specified, as a rapid-set will more than likely set too quickly in the bucket and skin over when tiling leading to lack of contact with the tile.

When selecting a grout for a wetroom, consider whether further hygienic waterproofing protection is required.  If so, an epoxy grout, such as BAL Easypoxy AG, may be the answer.  Impervious to water, easy to install, and easy to clean, epoxy grouts provide complete protection against moulds, staining and water ingress.  They are also required as standard in areas such as steam rooms and saunas.

As well as taking all the factors into consideration, we would recommend checking with the adhesive manufacturer to ensure that you are selecting the correct adhesive and grout for your new project.

BAL’s Technical Advisory Service is on call every week day from 8am to 5pm and can provide NBS specifications, product support, project solutions and advice.

As the market-leaders for tiling solutions, BAL also has a nationwide team of Product Support Technicians who can provide on-site consultancy to your installers or designers.
To find out more visit: www.bal-adhesives.com

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