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Question:

Do I need to water seal a cement board that would sit behind tiles in my shower before i tile it?

i would also like to know what products might help me. Thanks :) Oh, and the type of board i got is called hardi-bord... i didnt know if that might help.

Answer:

if using a hardi board then u do not need to treat it with a water seal before or after hanging as it is made of cement, but u will need to use a mesh tape and a morter type mix to tape the joints and corners of the cement board ( just like doing drywall ) to stop any water from passing through those spots
wow, some of these answers are terrible, I like the one where the guy says dont worry about taping and mudding the seams or the other one that said just double up the backerboard lol. Anyway, you should have a vapor barrier of some sort. Since you already put up the backerboard, you should tape and mud the seams then put a coat of Redgard(made by Custom Building Products, at Home Depot) over the backerboard. You can paint it on, its very easy. As far as the electrical box, if it was dry before then I would leave it as long as its not wrapping around any plumbing pipes.
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