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jason37
09-14-2013, 05:09 PM
do i really need a vapor barrier i.e felt paper or 6mil plastic behind my cement board? never did in the past.

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Screw Loose
09-14-2013, 05:37 PM
Yes, a vapor barrier is always needed behind a cement board tile installation.

OR!

No vapor barrier behind cement board IF there is to be a surface applied product like Kerdi(fleece) or RedGard/Hydroban/etc.(liquid)

If there is no vapor barrier, then you have created a space behind the tile in the wall that WILL grow mold as the moisture permeates through the CBU.

cx
09-14-2013, 05:37 PM
Welcome, Jason. :)

For a shower that is not a steam shower, you do not require a vapor barrier in your walls. But you must have either a moisture barrier behind your CBU walls or a direct bonded waterproofing membrane on the inside surface, but not both.

That's been a requirement of the tile industry for longer than I been in it.

Are you building a traditional shower pan for this shower?

My opinion; worth price charged.

jason37
09-14-2013, 05:47 PM
yes this is traditional shower pan 4 x 3. i planned on red guarding cement board but i think i may just do vapor barrier also as added prtection. thanks for the advice.

Lazarus
09-14-2013, 06:54 PM
No, No, No.....You do one or the other....but not BOTH. With both, you end up with a "vapor sandwich" that will hold moisture back there!

Either vapor barrier on the studs before the board or NO vapor barrier on the studs, but a paint on waterproofing OVER the boards before you tile.... :bonk:

jason37
09-14-2013, 07:42 PM
that makes sense lazarus. i should have known that. i have been in the trade for 17 yrs. i am mainly comercial applications. still i should have known.