I came across this today during an inspection and it left me scratching my head. The home was built in the 70s and the roof decking has 2 layers of what appears to be gypsum board? The home has a metal roof (installed over 3-Tab shingles) you can see the underside of it through this hole. Have yall ever seen this?
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Never seen it before but I see no harm in it. It just deadens the sound of a properly installed metal roof. Don’t think it wil last all that long but I guess it depends on the climate. Sheet rock really doesn’t like moisture. I think I would write it as a less than ideal material with a shorter than normal lifespan.
Never any harm in saying you haven’t seen something before. “I’ve been doing this for 15 years and I’ve never seen that before.”
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Gypsum Panels, Water Resistant on Building Exterior Walls & Roofs
Gypsum Board Building Sheathing FAQs
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Is it a duplex or multi-family home?
It is a single family home
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Could be a lot of weight for that roof especially if in heavy snow areas.
What area are you in?
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That was my first thought too.
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Im down in Florida so not to much snow here. Just the occational hurricane to worry about.
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Guess they won’t be getting their roof to wall attachment credit.
Sheathing material has nothing to do with roof to wall attachment.
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In commercial it’s very common to do exactly that with a fiberglass gypsum product, the market leader of which is DensDeck® .
Using regular drywall is “nearly as good” at a “fraction of the price”, I imagine.
DensDeck® has fiberglass rather than paper and claims moisture resistance, but it still turns to mush if the roof leaks.
Ick. A permanent roof over a disposable roof. Those 3-tab just add weight.
It was late I misspoke. Good catch. Roof to deck attachment. You know what I mean though. Its not 7/16th plywood or osb. Not sure how a roofer would get away with not bringing it up to todays compliance unless they just do not have insurance.
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Is that a townhome? I see a wall next to it. If so it’s a fire break.
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I have gypsum wall sheathing with no tar paper behind my brick veneer. It can be very resilient.
Is that a screw-down metal roof? If so, where are the purlins for fastening? Sometimes, they will be attached atop the shingles, creating a minimum one-inch air gap between the shingles and the underside of the metal panel.
Ultimately, fastening is my only genuine concern, and the metal should not be directly in contact with shingles.
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During my building career, that was very common, Brian. It was normally this product here;
Since this was commercial building designed by Architects, it was typical to have all joints covered with asphalt mastic and all exposed cut joints covered. I have seen it left exposed and seen it with felt paper, depending on the designer. I always preferred using the felt paper because of all the brick tie fastener penetrations through the sheathing.
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Outside pics? Standing seam?
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As far as I know, we don’t have a lot of exterior gypsum applications in my area. Do you know if they used regular roofing nails to install the three tabs? It doesn’t seem like they would grab the drywall as well, like they do with plywood, especially during a hurricane. Perhaps that is why they added the steel roof.
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When roofing commercially, I installed 2 sheets of drywall on corrugated commercial roof decks back in the late seventies. Typically inverted BUR roofs.