It is my understanding that "green" water-resistant drywall should not
be used on the ceiling because it will sag.
It is also my understanding that green drywall differs from regular
drywall only in the paper covering.
So... why will green drywall sag more than regular?
After posting, I found a reference to the fact that the "green" drywall
core is indeed treated to be water resistant (as opposed to my previous
reading which stated that just the paper was resistant).
I now have this explanation:
"For ceiling applications, green board requires extra support.
According to Gypsum Association guidelines, green board in a ceiling
application needs 12" o.c. support.
If supports are 16" o.c., 5/8" green board should be used. Why is this
additional support needed? Moisture repellents, such as the asphalt and
wax emulsions in the green board core formulation, act as lubricants.
These lubricants cause the gypsum crystals to slip easily, resulting in
For bathroom ceiling applications, we recommend regular or Type X
board. Simply apply a good quality sealer and two coats of latex based
paint after installation."
So to redirect the thread: would anyone with experience care to give
their opinion on the suitability or necessity of green board on a
OK, that's the manufacturer's opinion on the suitability or necessity of green
board on a ceiling...
What, the manufacturer doesn't have enough experience to suit you? Do you have
a reason to suppose that the opinion of some stranger on Usenet is worth more
Bottom line: you already have your answer. If you want to put greenboard on
your ceiling anyway, nobody's stopping you. I'll tell you one thing, though,
that the manufacturer didn't: greenboard is a *lot* heavier than regular
drywall. I don't see any point in making the job of drywalling a ceiling any
more difficult than it already is.
Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?
I did a poor job of quoting. The first two paragraphs, suggesting using
12" oc support for green board on the ceiling (and the explanation) was
from the Gypsum Association guidelines. The third paragraph
(recommending regular or type x) was an addition from the website from
which I pulled the quote. That's why I was looking for more opinions.
That was bad form on my part, and I apologize.
Thanks for your answer.
To my knowledge, the gypsym core in green drywall has a chemical in
that makes it more resistant to water saturation, this also makes the
board less stiff. To prevent sagging in ceilings a common solution is
to "strap" the ceiling with 1x3 firring at 12 inck centers and then
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