This topic had come up before, but I keep getting conflicting advice
so I wanted to dedicate a thread to it.
When boxing in skylights, I being told that one does not want to use
drywall for the skylight window bay. The supposed reason: either the
hot air, or the humidity, or the intense sunlight will rot the drywall
over time and one ought to use plywood. In this newsgroup, I believe,
I only heard the opinion that this is either total nonsense or, at
best, obsolete old school idea.
So, if you do agree with plywood over drywall, please post your
opinion and your reasoning.
Many thanks in advance,
There are millions of porch ceilings in the south done in drywall,
that doesn't make it right.
Any place moisture is a distinct possibility, dry wall is a poor
choice. That is done because it is cheap and the installers will be
long gone by the time trouble arises.
I've lived in two homes with skylights for 25 years. Both of them
were done in sheetrock and never had any problems. Also, all new
construction I've seen here in NJ is done using sheetrock. I would
think this might be a regional issue. If you live somewhere that
gets very cold, then condensation could be more of an issue. Here it
was down to 2 deg last week, which is unusual, and no problems. BTW,
I have a humdifier as well.
But I would think that if the sheetrock around a skylight is going to
cause condensation problems, then it would be likely that you would
have other moisture issues as well and the humidity in the house needs
to be addresses as opposed to the sheetrock.
I'd say the main difference is the placement of a horizontal (or
nearly so) window directly above. I'm sure skylight are designed to at
least minimize leakage, but it is still less so than a roof.
One good hail storm and the design could likely change drastically.
All the skylights I ever owned weren't designed to minimize leakage.
They simply don't leak. And if they do, then they were installed
wrong or have failed and need to be replaced. I guess you could
prepare for possible catastrophic failure by shattering of the window,
but I think if that happens, you usually have bigger issues than
drywall vs plywood. In fact, I would probably rather have drywall
than plywood because not only is it less work to install initially,
even if you have to replace it following window failure, it's no big
To answer willshak's question, I'd say a skylight is different than a
ceiling with an attic or similar over it in this way. The attic will
have insulation between the cold attic space and the ceiling. In the
case of a skylight, the area of vertical drywall approaching the
skylight has minimal or no insulation. In my home for example, I
have skylights in a cathedral ceiling. The last few inches of
vertical drywall has very little insulation compared to the rest of
the ceiling. In that regard, it's like any other window. And all my
windows are finished with wood trim, not drywall. But as I said
previously, no problems here in NJ. I don't have condensation on
either the skylights or window trim.
Over the last 20 years I've been doing drywall I've done hundreds of
skylights with drywall and never had a problem.. The only water problems
I've seen is some of the cheaper off brand skylights have crappy flashing
kits that leak and homeowners trying to DIY and mess up the install..Bottom
line , get Velux or similar and follow the installation instructions to the
letter for the flashing kit and water shouldn't be a problem even in a
bathroom..I'm in Maine where it gets VERY cold (-25F) and condensation isn't
a problem either , even in the bathroom as long as you use your exaust fan
when showering...Sunlight does not rot drywall , by the way...Metal
cornerbead doesn't rust up like it used to years ago ..I do however recomend
using stainless steele drywall nails for the cornerbead in the bathroom ,
and basements too for that matter , to prevent rust spots bleeding through
the mud..I use them everywhere but that's just me..I get them by the box and
it's just easier than having 2 kinds....I also recomend using vinyl flex
tape instead of the steele backed tape to prevent rust spots on the 45
degree angles in baths and basements , I use it everywhere...Same reason..I
get it by the case and it's easier than carrying around 2 kinds...Good
Only if there is the possiblility of a lot of condensation forming on
the window that rains down, (like a bathroom skylight in winter).
Otherwise drywall is fine. Around any bathroom window, in cold
climates, plastic drywall corner bead is better because the rust
stains wont come through as the metal corner bead will rust. The
metal corner bead is more a problem than the drywall itself when you
have raining window condensation in winter.
Not sure about all that--- but whichever way you decide to go, make sure you
pick up three or four plastic buckets to store in a closer beneath where the
skylights will be installed.
Then you won't have to scramble far to get something to use to catch the
dripping water when it rains.
It's just preference and or cost factor.
I've never seen plywood used. I have seen 1"x material used (oak, poplar,
pine). A 3/16" reveal is left on the 1" all the way around, and cased out
similar to how doors & windows are cased/trimmed.
If you're getting condensation, that's the problem which needs corrected.
Back in the stone age, when the frosted bubble skylights (which have
lotsa humidity problems) were popular, my father always recommended to
clients that they be cased out in whatever wood the room was trimmed
with, with a water-resistant finish. He always put the bubbles up on
about a six-inch curb to aid in waterproofing, and most were on the
then-popular 'California Style' T&G over beam Flying Wing roofs. Made
the 'tunnel' up to them about 8-10 inches, doable with 1x planks or
cabinet-grade plywood. Not many skylights on 5-12 dipped-in-brick
Cleaver houses, or 12-12 colonials. (T&G 2x, plus 3" celotex under
tar'n'gravel hot mop, made for roof snow melting very fast. I notice a
lot of California roofs here in snow country are now a lot thicker, with
new edge trim to hide the 8+" of foam panels that were retrofitted under
the new membrane roofs. Natural gas was a lot cheaper back then....)
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