I’m thinking of using 5/8 TG advantek for my roof sheathing instead of plywood with H clips. My rafters are 19.3 oc. My rep says this is fine but I’m wondering if it is better than the plywood and if it will be difficult to install on my 5/12 pitch. Any thoughts?
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I know in certain parts of the country, either you have to use T&G sheathing on the roof or block all seems. This is for either wind loading or seismic loading. I've heard good things about Advantec.
What parts of the country would that be?
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My part, actually (Melbourne, Florida). I'm not sure if it's officially code or not, but the engineer (engineered drawings are required to get a permit here now) I use specifies blocking at ALL plywood seams that don't fall on a stud.
We'll see how it works out. I just finished the framing of a detached 2-car garage, and hurricane Frances is making it a bullseye at the moment. If anything bad happens, I'll post pictures. I'm vacating the are tomorrow for Tampa and am hoping for a miss.
Andy
Is that on roofs as well as walls?
not trying to pick an argument. just after info and understanding. I'm trying to conceptualize what shear benefit there is in doing this.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Didn't Mike Smith said they had to do the same...? (T&G or blocking)
Matt
Edited 9/1/2004 10:39 pm ET by DIRISHINME
Yes, the engineer specified blocking on both wall and roof plywood joints. The nailing schedule was 4" on the edges and 8" in the field. This is for standard 4-ply CDX plywood.
Piffin,
My understanding (whatever that means :-)) is that in some cases, for the roof to be considered a diaphram, the panel edges have to be blocked. Similar to shearwalls. The ply, or osb can buckle in earthquakes and heavy winds. I know in Seattle (or subarbs), WA, a friend of mine who used to frame with me told me they had to have shear nailing inspections on their floors, then walls, then roof before it could be covered. He said either T&G or blocking was required for the roof. They had to nail 3" OC into the birdblocks and the birdblocks had A-35 clips nailed to the block and the top plate (plus the hurricane clips). This is all to transfer the roof diaphram loads to the shearwalls, which had to be connected through floors into holddowns embedded into the concrete.
I know that in some cities where we build, if we leave the roof sheathing short for vent a ridge, they want metal straps nailed to the rafters up and over the ridge and to the rafter on the other side, even if we have collar ties. It's usally a strap every other rafter or every third.
I have no idea if this is making any sense :-) I'm getting ready to leave in the morning for a weekend at the Gorge, WA for 3 days of the Dave Mattews Band and I'm excited to get away :-)
A little sense.
It seems to my little mind that the diaphraghm woul dbe better preserved with good nailing to prevent the ply sheathing from buckling. I suppose the blocking is a redundant insurance kind of thing - partly a throwback.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Piffin,
In Thor Matteson's book on shearwalls, he explains how all of a shearwalls strength comes from the nailing around the ply edges. If you only have a nail every 16 or 24" OC on roof sheathing on the 8' edges, it significantly reduces the strength.
You know, what gets me is how many nails we use and we think it's good enough. I saw a video, I think it was at Halsteel's website, of a 3 story wall that Simpson built and then shook. You should have seen it and heard the noise the plywood made. I'll see if I can dig it out and post it. I think that most of us have underestimated the forces that high wind or siesmic activity put on a building. I find all of this interesting, even though a lot of it is difficult to understand :-)
Didn't take as long to find it as I thought. Here is the link to Halsteel's webpage and the racking test is at the bottom. http://www.halsteel.com/trackers.html
I recognize the picture in that test from a History Channel "Engineering Disasters" episode (#7 IIRC). The structure is a full scale model of part of the Northridge Meadows apartment complex that failed in the 1994 earthquake. The shake table facility is at U.C. Berkeley, and it's playing back the actual measured shaking of the Northridge quake. The ground floor was mostly parking, open on one side, and it failed and the rest of the building pretty much just sat down intact. The fire department drove by it and didn't notice anything wrong because it looked like a pretty much OK two story building. I remember hearing back then that they found that 10d nails had been used where 16d should have been used.
-- J.S.
I occasionally see requirements for edge blocking on prints.
Like you, I wonder how much good it does. If the plywood is nailed well I doubt it's necessary in all but the most extreme cases.
I doubt it will go away anytime soon. Everyone is concerned about liability, so they're gonna overkill things in order to cover their butts.I won't rise to the occaasion, but I'll slide over to it.
Try the search function here, someone mentioned using it on a roof a little while back I believe.
I am assuming this is tongue and groove..........
don't nail down the previous sheet to well esp. along the side where the next sheet need to catch on. It's not fun doing t&g ply on a roof. Just my opinion though.
Eric