Devedander
New Member
So the most common advice I have come across when waterproofing cement backer board involves some sort of water proofing solution like Kerdi or Red Guard but something that I am still unclear on is how the backer board is installed slightly above the tub flange...
If you paint a waterproof substrate onto the backer board and water gets through the tile/grout it will run down the backerboard and then it seems to me it the surface tension would cause it to run under the boards lower edge and to the studs/behind the lip of the tub...
Am I missing something here?
Doesn't this issue mean a water proof membrane overlapping the lip is still needed?
Also if the water does run down on to the tub lip where does it then go? It seems like it would have to run all the way around the edge of the tub and dump down the from of the tub into the floorboards/wall?
Thanks for any answers!
If you paint a waterproof substrate onto the backer board and water gets through the tile/grout it will run down the backerboard and then it seems to me it the surface tension would cause it to run under the boards lower edge and to the studs/behind the lip of the tub...
Am I missing something here?
Doesn't this issue mean a water proof membrane overlapping the lip is still needed?
Also if the water does run down on to the tub lip where does it then go? It seems like it would have to run all the way around the edge of the tub and dump down the from of the tub into the floorboards/wall?
Thanks for any answers!