Densarmor Gypsum Board for Basements
A contractor recommended using Dens Armor interior gypsum wallboard instead of the USG mold-resistant green board. Has anyone used this before and are there any concerns with breathability, allowing the basement walls to breath?
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No issues with drying or vapor permeance--it is over 10 perms, so it is basically vapor open. Using paperless gypsum is a step better than 'mold resistant' paper faced drywall. If you have a Fine Homebuilding account, an excellent article covering working with this material.
Fight Mold With Paperless Drywall
I completed a basement reno 10 years ago using it. Only thing I can recall being different at the time was the surface texture felt a bit like shark skin. I was a bit concerned about the texture difference between field and taping/mud areas showing, but everything finished out very nicely. Far as I know, the walls are doing fine since I have not heard otherwise.
The green board paper will ripple if it gets moist enough. I have also found some sheets to be unfriendly to taping mud thanks to the moisture treatment. The mud kind of slides around a bit on some sheets. Maybe the ones that got extra water resistance treatment.
At the time Dens Armour was a noticeable upcharge, but the client wanted to be sure no mold could take hold. The regular paper faced materials removed were quite grotty, so I guess it must be holding up well if I have not heard of any issues.
oops : should note much exterior work was done to control grading and rain runoff, which stopped the surface water from over flowing the brick ledge. Simply having the stepped foundation much drier than before might have allowed for regular drywall. Still, the fiberglass mat surface won't support mold and the client is happy.
Much appreciated Kohta and Roger, thank you! The contractor is also saying he can only find 5/8" instead of 1/2". All of the articles I can find on GBA all list 1/2". Is 5/8" acceptable too as far as the breathability?
Just corroborating the difficulty with sourcing 1/2" paperless. I had ordered it for my own basement and even though it's technically a product, apparently 'no one' buys it, leading to scarcity in normal distribution channels.
Seems like paperless is almost exclusively used in commercial where 5/8" is the norm.
I have it installed mostly in semi-finished spaces where I didn't care about taping telegraphing or appearing different than the wall surface. Where I have it in finished spaces (e.g. covering a masonry chimney since paperless drywall is noncombustible), it will be skim coated so that it finishes properly.
Densglass and Densarmor are commonly used commercially, but rarely in the residential world. That's probably why you're having a hard time finding it in 1/2". In the commerical building world, everything is 5/8" pretty much everywhere. 1/2" doesn't meet fire code requirements.
The material is commonly used in wet areas and shouldn't be a problem, it's basically a paperless drywall. The main issue you'll have is the rough surface, which you'll probably need to skim coat prior to painting. Aside from that, and being more difficult to cut, it's not much a problem to work with.
I'm going to try to do the 'teach a man to fish' thing here:
For these purposes, 'vapor open' or 'vapor permeable' is anything 10 perms or higher:
BSD-106: Understanding Vapor Barriers
Vapor impermeable: 0.1 perm or less
Vapor semi-impermeable: 1.0 perm or less and greater than 0.1 perm
Vapor semi-permeable: 10 perms or less and greater than 1.0 perm
Vapor permeable: greater than 10 perms
If you take a look at the GP spec sheet, you will see that all thicknesses are listed over 10 perms. In reality, the numbers are higher: RDH measured 5/8" glass mat gypsum at 17 to 28 perms:
Trends and Anomalies in Hygrothermal Material Properties from the ASHRAE 1696 Research Program
If you want a resource to understand what these 'perm' things are, check out this column:
BSI-099: It's All Relative
Just remember that fiberglass drywall can also mold. You still need to ensure reasonable moisture levels. Sometimes gypsum boards are being delivered with mold already inside.
Thank you everyone, much appreciated for the thorough and helpful responses!
I think it's a great choice.
But may I suggest posting more details of your wall assembly? There are lots of other ways to screw up and have mold and moisture problems in other parts of the assembly in basements. And if you get the other details right, you probably don't actually need the paperless drywall.