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Tanking A Tiled Bathroom Is Now Mandatory!

1 Aug 2018, 10:04 AM

Tanking A Bathroom

Tanking A Tiled Bathroom Is Now Mandatory…

Latest codes of practice released in July 2018 by the British Standards Institute (BSI) for BS 5385-1 (wall and floor tiling in normal internal conditions) has seen a positive change in regulations overseeing works in domestic bathrooms and wet areas.

Under the new revision by the British Standards Institute (BSI), In clause, the standard states that ‘In wet areas … substrates should be protected with a suitable proprietary tanking membrane system’. It further declares that ‘the weight capacity of the tanking system should be capable of carrying the load of the tiles and adhesive’. All substrates within a wet area should now be waterproofed before tiling, even in domestic locations.

British Standards already supported waterproofing in commercial wet areas, but under the new BS 5385-1:2018 clause for "Tanking", it will now also be recommended to waterproof domestic locations as well. So, whenever you're retiling a bathroom, shower, or other wet areas, remember you must apply a suitable tanking membrane, tanking solutions or apply waterproof tile backer boards first.

What areas needs Tanking?

A wet area is considered to be any wet-room, bathroom, shower area, steam room or any other location that is subjected to frequent water contact. This would include the walls and floor in a wetroom, walls within a shower cubicle and walls around a bath with a shower.

Although these rooms/spaces tend to be tiled, the substrates the tiles are being fixed to (such as plaster, plasterboard, or some proprietary backer boards) are often moisture sensitive. The British Standards now advocate the use of tanking membranes, tanking solutions or waterproof backing boards (not moisture resistant plaster board) to protect them.

Do I really need to add a tanking solution?

Not following the BSI guidance can become costly. With the new standards in place, you could find your home insurance void and invalid for water damages including the tiled wet area and adjoining rooms.

Tiles alone are not enough to stop water from getting through to the substrate. It is a common misconception that cementitious adhesives and grouts are waterproof, however, most are only water-resistant. Cementitious adhesives and grouts are popular choices for fixing tiles, and their porous nature allows moisture to pass through. Over time, water is absorbed through the grout joints and adhesive bed, and then into underlying substrates.

If the substrate is unprotected, it can lead to damp and mould issues. As time progresses, this can even cause problems with adjoining rooms and/or cause tiles to de-bond which can become a costly situation to repair.

What type of tanking do I need?

There are a couple of different options when it comes to tanking a wet area.

Paint on tanking solution. This tanking solution paints overs plaster board, moisture resistant plaster board and other materials leaving a waterproof membrane once dried ready for tiling. There are a number of brands available including Tilebacker, Roman Shield and Aquaseal to name a few.

Tile backer boards. Tilebacker boards are waterproof and ready to be tiled onto. They also give a higher weight capacity and higher insulation valves over plaster boards and easier and faster to install as there is less tanking to pain on and less drying time. There are a number of brands including Tilebacker, Abacus Elements and Wedi to name a couple.

Weight Capacity of wall materials

In clause, the standard states ‘the weight capacity of the tanking system should be capable of carrying the load of the tiles and adhesive’. Below are some references to

Wall Substrates with maximum weight of tiling per m²:

  • Gypsum plasterboard with plaster skim                                                  20kg/m²
  • Gypsum plasterboard direct (without a plaster skim)                        32kg/m²
  • Plywood (WBP), no longer recommended as a tile substrate         30kg/m²
  • Gypsum fibre boards                                                                                      approx 35-40kg/m²
  • Waterproof Tilebacker boards (depending on brand)                       Up to 62kg/m² *
  • Glass reinforced cement sheets                                                                 up to 50kg/m² *

* Dependent upon the brand and thickness of the board.

Paint on tanking solutions often do not affect weight capacity of the wall, for example painting a plaster board wall with tanking solution would give a weight capacity of 32kg, but this does vary from brand to brand. Please ensure the correct solutions is used.

Which Tanking Option Is Best?

For most situations, Tile backer boards (or similar brand) offer the best solution as they offer a higher level of weight capacity, waterproof as standard, fast to install (saving labour time) and less messy. Tiler back boards are perfect for use instead of plaster board should you need to replace the plaster board after removing old tiles.

If your walls are already perfect and have new plaster boards on them, a paint on solution would be the obvious option unless you intent to install large heavy tiles.

Each solution will offer the protection you need to comply with the BS 5385-1 regulations.

Other Changes Worth Noting

  • Removal of plywood as a substrate for wall tiling.
  • Increase adhesive coverage requirements
  • Minimum Grout joint widths standards

Foot Note

We hope you find this information helpful. Should you wish to learn more or purchase tanking solutions please visit out website for more information.

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This guide was created for reference only. can not be held responsible for injury or damage caused if you decide to use this method.

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