Glass mat drywall for bathrooms
tjones1014
| Posted in General Questions on
CZ 3A/4A (N GA area) – 2001 gut reno
We had a holistic contractor recommend using glass mat/fiberglass-faced drywall in wet areas like bathrooms and laundry rooms. We’d like our assembly to be able to dry to the inside, as we live in an area with a predominantly inward vapor drive (please correct me if I’m wrong here).
Would this kind of drywall hinder interior dry ability? We would most likely use typical latex paint you’d get at big box stores.
Here’s the rest of our assembly for reference:
Hardie, rain screen, Tyvek commercial, OSB w/ taped seams, Rockwool
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Replies
If you're talking about something like Densheild, I recently looked up it's perm rating. I believe its 1.5 perms. So still a little vapour open. I wouldn't worry too much about it.
But look up the proposed product spec and find the perm rating. Remember that inward drying issue is only a 'potential' issue on exterior walls, which I will assume is 1 of 4 walls of your bathroom and laundry room. Also how small the rooms are can also play a factor.
You also want to consider that your shower area is going to see consistent water and vapour, so good protection to prevent consistent vapour into your walls is important. Depends on your system design.
Personally speaking I love the general durability of Densheild and wish it wasn't so expensive because I would use it in more spaces than just the shower. And In general I hate today's drywall, it's such garbage of a product.
Jamie
I'm not sure what brand our drywall guy is using. What perm rating would be considered still open enough to dry effectively? And how would adding latex paint affect that perm rating?
Yes, there is one exterior wall for our bathroom, and one exterior wall for our guest bathroom. Both are pretty small.
Thanks so much!
tjones,
If you have enough moisture accumulation to affect the drywall in either a laundry or bathroom, that needs addressing as it will cause other problems. Using drywall alternatives designed to repel water isn't necessary or a good solution.
So you're saying it would be better to use regular paper-faced drywall in bathrooms & laundry rooms, is that correct?
tjones,
Outside of areas that expect direct contact with water - that is showers, and backsplashes - surfaces in a house should only be exposed to high humidity. You need to control that humidity, not rely on the materials. So yes, I don't use anything but regular drywall anywhere except those two very circumscribed situations.
To clarify, you said you use regular drywall everywhere except the bathrooms and laundry room. So what do you use in those areas?
Agreed, controlling humidity in those rooms is a priority. I think our consultant had mentioned using fiberglass-faced as a safeguard in case we run into any humidity issues. Or say if someone is washing their face at the bathroom sink, if water gets on the drywall. Instances like that.
tjones,
No, maybe I as unclear. The only places I use materials other than regular drywall are shower surrounds and backsplashes. What I use there depends on what the finished surface will be. Laundry and bathrooms get drywalled.
National Gypsum Gold Bond XP for bathrooms, but I second Malcolm’s points about moisture and any form of wall board receiving such moisture as very concerning.
A practical consideration when using glass-faced board on the interior is that the finishing of such a product gets costly, because you have to skim coat the entire surface (similar to plastering).
I would not use "regular" gyp board in a bathroom. In fact, in some areas code requires use of moisture and mold resistant gyp (purple faced board) or the mold resistant gyp (green board) in bathrooms. There are also paperless gyp products that are mold/moisture resistant. All of these are intended to be taped, finished & painted.
DensShield is a light weight backerboard for tile (instead of cement board) with a moisutre barrier - it is gray. It is not intended to be taped, finished and painted although it can be floated to match the adjacent gyp if it extends a few inches past the tile.
DensGlas, a bright yellow fiberglass product, is used as an exterior sheathing, usually on commercial projects where the sheathing does not need to function structurally.