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Unread 03-19-2008, 07:58 PM   #1
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Bathroom Remodel Questions

First things first. Great forum!

Remodeling bathroom and I would appreciate any comments or suggestions to the below method/plan I have for installing a vapor barrier and CBU behind tile in the tub/shower area:

Bathroom has two exterior walls, with a side and end of our three-wall alcove bathtub running along those walls. I have installed a single sheet of 6mil poly on the exterior walls (walls insulated (6", R-19, with non-faced fiberglass batts) that run the length and width of the tub (inside tub area). The rest of the exterior walls on the outside of the tub area are insulated with Kraft-faced fiberglass insulation. The poly was stapled to the studs; staples have been covered with tape along the length of the studs, and the ends and top of the plastic sheet (top and sides) were sealed with a bead of silicone caulk and then taped along the length of the top plates and wall studs. I plan to install 1/2" hardibacker under ceramic tile in the tub/shower area. For the rest of the bathroom I plan to install 1/2" DensArmor - ceiling, walls.

Questions: Do you foresee any issues with this combination of plastic vapor barrier and CBU in the tub/shower area? Should the poly sheeting extend below the tub to the floor on the exterior walls, or should it end at the tub lip and sealed with caulk. If I install the poly down to the tub lip, do the exterior wall spaces below the tub lip to the floor require a vapor barrier. Should the spaces around the plumbing (shower head, faucet valve, etc) be filled before I tile around those areas. And finally, what is the best method for taping/sealing the joints between the hardibacker board and the DensArmor boards?

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Unread 03-19-2008, 09:09 PM   #2
Tile Contractor -- Jacksonville, FL.
Join Date: Oct 2007
Location: Jax., Fl. (Dinsmore)
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Vapor barrier/ CBU sounds good.
Run your poly over the tub lip and seal with silicone. No vapor barrier required elsewhere.Only put poly over unfaced insulation.
You can just caulk your fixtures that don't have a rubber seal on them that are below the shower head.
I would tape the boards like normal drywall.
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Unread 03-19-2008, 09:49 PM   #3
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Thanks for Reply!
I'm still uncertain what I must do with the exterior wall spaces that run below the tub lip. Those spaces are currently insulated with unfaced insulation. Since the poly sheeting above the tub is sealed at the tub lip, should I install a separate sheet that will cover the unfaced insulation in the wall space that runs from the floor - behind the tub -up to the tub lip?

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Unread 04-01-2008, 06:56 PM   #4
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Vapor Barrier Cinfusion

I'm still incertain how the vapor barrier should be installed behind the CBU. The tub is a three-wall alcove, with the two sides running along an exterior wall. Hand drawings in the attached file show three options with installing the 6 mil poly on the the exterior walls, behind the CBU. Please advise on the best installation.

With Option 1, I'm concerned with the horizontal seam (overlapping upper and lower plastic sheets) that would allow mositure penetration at that seam into the wall cavities. With Option 2, I'm concrened that moisture that may condense/collect on the plastic vapor barrier will run down behind the tub. And With Option 3, I'm concerend with moisture being trapped between the two sheets that overlap above the tub, though the space between those sheets will be virtually negligible.

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File Type: pdf Vapor Barrier Bathtub.pdf (18.0 KB, 227 views)
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