tile tub surround - existing insulation has vaporbarrier
 

Long story short, I'm ripping out some blueboard in basement for a future tile tub sorround and replacing with 6mil plastic and CBU. Or that was the plan. I just ripped out some of the back wall and realized (remembered) that the builder had installed insulation around all outside walls. I don't recall the type of insulation, but it seems to be faced batts with a white plastic sheet on top that spans the whole wall, not just stuffed between studs. This is only on the back wall, not the sides. So that brings me to the question... what should I do on this back wall? See attached pic for what is there. It's in fairly good shape other than the square i punctured out with the drywall saw when starting this process and a few small rips and holes, but that could easily be patched. If I just apply the 6mil over that, I assume Id then be stuck with the no good moisture sandwich.

Should I just use what's there (patched) as the back vapor barrier and then attach and extend the plastic on each side for left and right walls. Or I could remove the plastic and paper face from insulation behind the entire tub area where the CBU is going and stick to the original plan. Or is that space (none, really) between the 2 plastics not enough to cause a moisture lock issue? Any other ideas? Right now I'm stuck on what to do next. Thanks!

Rich

What type enclosure are you installing? If it's a nail on one then just leave up what's there now.

Tile surround - forgot to specify that

Is that an exterior wall?

I don't think that vapour barrier should be used as a moisture barrier for behind cement board.

I would still use cement board and proper moisture barrier behind it. It's so easy to do at this point.

yes, exterior wall. I've decided to remove the white plastic covering the insulation and cut a bunch of long slits in the faced insulation to allow for airflow, and then just continue as planned with the plastic barrier. Thanks for the input

No problem. Just saw your post on John Bridge as well. :wink:

yeap - i don't usually post all over the place, but it's a bit of a frenzy with this... baby on the way in about 2 weeks and trying to wrap this up before then.

Congrats on the baby! I don't blame ya for multiple posts. In fact, John Bridge is the best forum for tile advice.