Expert: Bruce E. Johnson - 11/7/2010

Question
I have a concrete block foundation. There is a french drain on the outside that goes down 3 feet to eliminate surface water.  I had a contractor install a perimeter drain on the inside along with an EZ-Breathe humidity remover about a year ago.  There does not appear to be any problem with moisture any longer.
I want to install a bathroom in this basement, but I am not sure about the proper materials for the walls.
I only have 50" wide by 9'3" long. To save space, I plan to use 3/4" pressure treated furring strips on 16" centers. Between the furring strips I'll use closed cell styrofoam 3/4" sheets.
If you think it wise I can frame a 1 1/2" wall with 1/2" dead space for ventilation.
In the tile shower area I will use concrete board. For the wall behind the toilet & vanity can I use regular dry wall or do I need to use greenboard?
Is there a reason to use plastic sheeting or would this be counter-productive?
Thanks,
Lou

Answer
Hi Lou, I would use either the green board or the new Pink board for the rest of the bathroom walls instead of regular drywall. Regular drywall is suggested for the ceiling however. Moisture resistant drywall needs special framing for ceiling installation. The furring strips and foam insulation are fine.  I don't see why you would need plastic sheeting.  You want the walls to breathe a little bit, the plastic may trap moisture or cause condensation to accumulate behind it however you will need a shower pan in the shower and good drainage to the shower drain.  I hope this information helps, please feel free to write again regarding this or other matters, sincerely bruce e johnson