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TnVolunteer
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# Posted: 6 Nov 2019 03:30pm
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Hey hows it going. Building a cabin for a family friend here outside of Nashville Tn. I believe I'm in climate zone 4. We get a little bit of everything here. My question is about my roofing options. Cabin is a 16x24, single level, stick framing. I had trusses built 18' wide and 3' tall at the peak. I'm using metal roofing, 36" wide standard stuff. My question is do I need 1/2" osb sheeting, or can I run 1x4 furring strips horizontally and mount the roofing directly to the furring strips? I have 2 reasons I'd like to run furring strips. First I'm working alone and hauling 1x4s up to the roof are much easier than 4x8 sheets of plywood. My second reason is condensation. From what I understand, condensation results from a change in temperature between the inside and outside surfaces. If I'm using a thin metal roof without a layer of sheeting, and have vents at each gable in, would this keep the temperature in the "attic" relatively similar to the outside temperature? I plan to insulate the ceiling, but no other parts of the roof. Can someone shed some light on this for me?
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Brettny
Member
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# Posted: 6 Nov 2019 03:54pm
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Furring strips should be fine. Venting depends on insulation. Use some type of metal roofing underlayment too.
Whats your pitch? Usualy metal roofing requires 3/12 minimum.
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NorthRick
Member
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# Posted: 6 Nov 2019 04:32pm
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I'd go with the sheeting, tar paper, then metal. It will be a much stiffer roof and that will make the whole structure sturdier. If you have the metal underside of the roofing exposed to the attic between the furring strips, you could get condensation on that exposed metal which might drip onto the attic insulation below.
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TnVolunteer
Member
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# Posted: 6 Nov 2019 06:21pm
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Thanks for the advice! I believe it is a 4:12 pitch. Rises 36" over a 9' span.
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AKfisher
Member
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# Posted: 6 Nov 2019 07:42pm
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I had the original plan to use fir strips, then changed my mind. Not wanting to cut corners on the build I then went with 1/2 osb and 30lb felt. My roof is steeper then yours and taller, but I would build it the same again if I had to.
I rented a pull behind bucket truck. Worked great and was much safer.
Since you are only a 4/12 (walkable) maybe rent a manlift, could put the plywood in the lift and and get it to the eave.
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TnVolunteer
Member
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# Posted: 6 Nov 2019 08:11pm
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On the previous 2 cabins I built I went with 1/2 osb, vapor barrier, and then metal roofing. But both of those roofs were exposed to the living area. As usual, the budget allows for a ladder instead of a man lift :D Oh well, I reckon I could use the exercise, I'll sheet in osb and cover it in house wrap with the rest of the walls.
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toyota_mdt_tech
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# Posted: 6 Nov 2019 08:38pm
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Quoting: NorthRick I'd go with the sheeting, tar paper, then metal. It will be a much stiffer roof and that will make the whole structure sturdier.
Dittos, use the 50# felt and get screws that poke all the way through sheating. Fatter ones hold better.
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ICC
Member
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# Posted: 6 Nov 2019 08:56pm
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Roof sheathing makes the roof assembly more rigid against wind forces. 5/8" is better than 7/16".
Not all metal roofing panels are rated for structural use. That is the usual job of the osb or plywood roofing panels.
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toyota_mdt_tech
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# Posted: 6 Nov 2019 09:44pm
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Quoting: ICC Roof sheathing makes the roof assembly more rigid against wind forces. 5/8" is better than 7/16".
Absolutely and I'd go one better and use plywood vs OSB, the thicker sheathing gives more bite for screws and when they do sweat, they wont turn the OSB into sponge wood around the screws
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Brettny
Member
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# Posted: 7 Nov 2019 06:16am
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Plywood is far better than OSB. All the roofs that i have done at my place with OSB are spongy but dry. I did my rough cut car port in pkywood because it will always be exposed under. The roof is flatter and more firm.
You shoud really price things out as part of your decision process. And price then out fron many sources. I found 1/2in plywood to cost only $3 more than 7/16 OSB. I also found the local lumber yard cheaper on every piece of lumbet becids 2x4x8ft. I also found the local lumber yards tar paper has lines every 2in. So you get that on streight and shingles go up like a breeze.
If your going to insulate the bottom of the roof rafters you should look into the "wrap and strap" method for roofing/sheething.
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Absolutely
Member
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# Posted: 7 Nov 2019 11:50am - Edited by: Absolutely
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I'll add that I also used 5/8" plywood sheathing under my steel roof. The only problem I had was that it was harder to source the Simpson 5/8" sheathing clips than the 1/2" clips. I also used ice and snow shield as my underlayment. It made the roof watertight while I was waiting for my roof order to be delivered.
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SE Ohio
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# Posted: 7 Nov 2019 12:41pm
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An old related thread with a link to some Info. Metal roof manufacturer might also have some guidelines for successful install
http://www.small-cabin.com/forum/2_6698_0.html#msg98496
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spencerin
Member
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# Posted: 10 Nov 2019 10:08pm
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I recently had an Amish crew build my cabin. What they did was attach 2" x 4" horizontal furring strips to the framing (like you suggested), pull bubble wrap radiant barrier tight over the framing, and screw the metal roof into the framing, with closure strips at the peak only. I like this setup for many reasons, and think it would work well for you based on what you're looking for.
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