Boxing in skylights

Hi,
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,
Aaron
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on 1/20/2009 2:24 AM (ET) Aaron Fude wrote the following:

Perhaps all the contractors have never consulted the person that told you that .
--

Bill
In Hamptonburgh, NY
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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.
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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.
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on 1/20/2009 8:58 AM (ET) Eric in North TX wrote the following:

What is the difference between the construction of skylights and ceilings with unheated attics above, or outside walls ? Skylight bays should be insulated as well as those ceilings and outside walls.
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Bill
In Hamptonburgh, NY
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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.
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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 deal.
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.
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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 luck...
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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.
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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.
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I take it you don't have any skylights in your trailer.
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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.
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Aaron Fude wrote:

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....)
-- aem sends...
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