I plan on building a shower with one wall up against an exterior wall. For space reasons the tile backer board will be attached directly to the exterior wall studs. Normally I would put a vapor barrier over the fiberglass insulation in the wall, but I know you are not supposed to put a vapor barrier on the outside of a shower to prevent moisture trapping. So, vapor barrier or not? Code for insulation says yes, shower builders say no. Will the shower tiles act as a vapor barrier for the insulation? Or does the wet shower environment make an insulation vapor barrier even more important? Shower will be tile with FusionPro grout on Densshield board.
shower on exterior wall
- Thread starter ianmck
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I’m a plumber so my answer is “ yes “
is the plumbing already on the outside wall???
If not I would keep it in a warmer area
If not I would keep it in a warmer area
Ok
Yes to what?
So, vapor barrier or not?
I've never used DensShield tile backer, but Georgia Pacific says it is "the first backer board with a built-in moisture barrier". Then it says it "absorbs less water than the leading fiber board". So apparently is does absorb some water.
There are contradicting views on putting a vapor barrier behind the backerboard on a shower. Cement board manufacturers recommend installing a moisture barrier behind the backerboard, while some tile contractors say no.
I've usually used an 8 mil Polyethylene sheet behind HardieBacker fiber cement board. I would use that in your case if I was doing it, even if DensShield says it has "a built-in moisture barrier".
There are contradicting views on putting a vapor barrier behind the backerboard on a shower. Cement board manufacturers recommend installing a moisture barrier behind the backerboard, while some tile contractors say no.
I've usually used an 8 mil Polyethylene sheet behind HardieBacker fiber cement board. I would use that in your case if I was doing it, even if DensShield says it has "a built-in moisture barrier".
I've used DensShield for the past 15 yrs on shower enclosures. Have not had a single problem.
Did you use a vapor barrier behind the DensShield?
On outside walls, yes.
Thanks for those responses. If I assume that there will be some moisture penetration, then it is a choice between keeping the insulation dry, or letting the Densshield breathe. On balance I lean towards the opinions above, to use vapor barrier on the one outside wall.
