Shower Vapor Barrier Repair

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NewGuy

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I used standard duct tape to repair a tear in the vapor barrier. I overlapped the tear a little and used the duct tape to hold it together. I read somewhere online not to use duct tape but to use Tyvek tape. There will be holes from the screws and a few staples anyway (staples only on top of the wall near the ceiling). I figured the vapor barrier was not 100% sealed so duct tape would be fine. This is for a walk in shower with a fiberglass pan. I am using 1/2" hardibacker board over fiberglass insulation and will be tiling the enclosure. One of the tears in the vapor barrier is in the very corner about half way up the wall.

Should I look for another repair method or will the duct tape work? Any help would be appreciated.
 

Jadnashua

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FWIW, duct tape is not really any good for ducts because the adhesive dries out and it no longer makes a good seal. You would be better off with something designed to be permanent, duct tape is not. Now, depending on how big the hole is, it may not make much of a difference anyway. Hard to say without a good overall picture. Does the insulation have it's own vapor barrier? If so, does that mean you now have two layers? Not necessarily a great idea.
 

NewGuy

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FWIW, duct tape is not really any good for ducts because the adhesive dries out and it no longer makes a good seal. You would be better off with something designed to be permanent, duct tape is not. Now, depending on how big the hole is, it may not make much of a difference anyway. Hard to say without a good overall picture. Does the insulation have it's own vapor barrier? If so, does that mean you now have two layers? Not necessarily a great idea.

Thanks for the reply. There is a slit about 2 inches long in the corner and a small tear about the size of a quarter also in the corner. I removed all the kraft (vapor retarder) facing from the insulation before installing it. I have only hung one cement board so I can remove it and replace the 6 mil poly (I have plenty of it). It seems like it is hard not to tear the poly with the sharp edges of the cement board. Unfortunately, I hung the Sheetrock first so I only have about a 1/8" gap on each side to fit it in.
 

Dana

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The adhesive on duct tape won't cut it for the long haul, but the adhesive on temperature rated foil tapes or housewrap tapes will.

But even if it fails, as long as the damage is only a slit and not a folded over flap the effect it's still a very good vapor barrier. Vapor permeance is all about the total amount of area. Even though the slit is a potential air leak (which could be a moisture transport problem, if your walls leak air elsewhere), it will still block water vapor permation into the wall, since there's almost no area involved.

There was no need to strip the kraft facers on the batts. Kraft facers run about 0.4-0.5 perms when bone dry, but are 5-10 perms when they reach moisture levels capable of supporting mold growth. Having them in place would have helped a bit on the air-retardency AND vapor retardency front with nicks or gaps in the poly sheeting, but that's all water under the bridge now.
 
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