Vapor barrier in garage ceiling
We had a major leak in our shower due to a bad tiling job and had to demo the entire thing to check for water damage and mold.
Before closing everything back up I am wondering what we need in terms of a vapor barrier.
The bathroom is above a fully finished garage. The insulation when built was a couple inches of closed cell spray foam with rockwool batts beneath it to fill the cavity. We had to take out the spray foam to check for water damage. I remember the insulation company telling me the closed cell spray foam acted as a vapor barrier between the garage and the living space above.
Seeing as it is such a small space, I would prefer not to have the insulation company come back to spray foam it again. We did not have to open up the garage ceiling so the only access is through the shower floor.
I am concerned about not having a vapor barrier for this section before we close everything back up. What are my options aside from opening up the garage ceiling and having it spray foamed again? Could I put a vapor barrier underneath the subfloor before we close it back up, or would that potentially cause problems? I do plan to put the rockwool back in there.
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I would look into getting a small DIY spray foam kit and spraying from above.
What climate zone are you in? And what vapor are you worried about?
I am in climate zone 6b. I am worried about the cold air from the garage meeting the warm air from the living space above.
The garage is insulated and finished but can sometimes get down to 30-40 degrees (or colder if the door gets left open).
so you are more concerned with having an effective air barrier. I think if you are diligent with how you seal up that hole and connect the substrate to you existing sprayfoam or even put down a membrane before your substrate that give you this air barrier you will be fine. Keep in mind that your shower is already basically a vapor barrier. You just need to keep your interior air interior, and you already have a vapor barrier (or at least you should! hopefully this tile job goes better...). Its not as if your subfloor is the first condensing surface for your garage, your garage sealing (gyp) is your first condensing surface for your interior air.