Waterproof bathroom

[henry1]

It is recommended to use a cement board to tile upon in a shower area because tiles can let water through. Apparently, the cement board does allow moisture through but its advantage is that it doesn't deteriorate in water, unlike the usual plasterboard.

So if that's true, then moisture goes through the tiles and the cement board and can start rotting whatever is behind (stud wall)? The tiles may not fall but the whole wall can...

And if water goes past the tiles and gets stopped by the cement board (or tanked plasterboard), where does it go? Wouldn't it drip down between the cement board and the tiles to the floor and?

 

[rules&rulers]

Its to do with microscopic moisture getting behind the tiles via the tile grout. Most tile grout is porous,, (including so called waterproof grout) the moisture/condensation that gets behind the tiles will damage the gypsum plaster resulting in the tile adhesive parting company with the gypsum plaster and tiles becoming loose.

Problems can arise after a period of time (well after installation) and depends on how well the tiles have been fitted,ventilation,frequency of showering and if the wet shower surfaces are dried afterwards.

With cement boards the tile adhesive will not part company with the cement board as the board is more robust although moisture,condensation and mould can still build up.

On plasterboard walls to prevent moisture/condensation then a better grout is required ie 2 part epoxy resin grout as used on wet room tiled floors.

So cement board backer and 2 part epoxy resin grout,2 part epoxy resin adhesive,correctly fitted (although expensive) is the long term answer.