If tile is set over cement board and the grout leaks/wicks water , which it does slightly I am told, and the cement board also wicks water slightly, why dont building codes require some type of slight ventilation ,even if natual, behind shower walls?
Same for the wax ring area under toilets – if no leak but condensation seems some thru floor ventilation even a 1 inch hole would remove water/condensation
Edited 7/29/2009 8:37 am ET by edwardh1
Replies
The theory is that it wicks back out the same way it came in during the "dry spells" between showers, so that you don't need auxillary ventilation.
The reality is that it doesn't work that well, so someone invented Kerdi membrane to force the issue.
-t
Moisture will seek the drier environment; i.e., the space behind the walls, instead of the bathroom. The humidity in interior living spaces are very high when compared to the wall cavities.
For showers what webted said. For toilets only caulk the front half.
Normally there will be a barrier between the cement board and the framing. 6-mil poly or tar paper. That will prevent moisture from getting into the framing bay/insulation. From then on out it's what the other fella's said, during drying cycles the water exits through the cement board/grout and back into the living space.
When wetting exceeds drying (cracked grout/tile admits water too easily), or the wall is improperly detailed and/or constructed, that's when problems occur.
This was why products like Kerdi were invented so if you really wanna do a "top notch" job thats the route to follow!
View Image
The Woodshed Tavern Backroom
The Topics Too Hot For Taunton's Breaktime Forum Tavern