I would like to replace the shingles with metal roofing on my older Panabode cottage
I plan to install nailbase and new metal roofing on my log home.
I found this answer provided to a similar earlier question:
“Before reading your question, I had never heard of Pan-Abode homes. (For GBA readers who are curious, Pan-Abode is the name of a Canadian company that sells kits for building log homes — specifically, log homes made from milled logs.) To improve the R-value of your roof assembly, you can add insulation on the interior and then install a new ceiling, or you can add insulation on top of your roof deck and then add new roofing. Since you are planning to add new roofing, it sounds like it would be easiest to install rigid foam insulation on top of the existing roof sheathing, followed by a new layer of roof sheathing (or strapping) and new metal roofing. Another option is to install nailbase (a sandwich of rigid foam and OSB, like a SIP with OSB on only one side).”
I like the idea of installing nailbase, but have a related question. The roof of the cottage is tongue and groove 2″x6″ cedar. I assume I would have the OSB on top and screw the metal roofing to that. How would I attach the foam to the 2″x6″ cedar ceiling? Would adhesive be sufficient?
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Replies
Barney,
If you plan to install nailbase on top of existing 2x6 roof sheathing, the nailbase must be fastened to the rafters or the sheathing with long screws.
For more information on this topic, see How to Install Rigid Foam On Top of Roof Sheathing.
Barney,
Over the years I've built eight Pan Abodes and renovated many more. The standard roof construction is as you say 2"x6" t&g decking on flu-lam beams spaced about five feet apart. Above the decking is 2" of foam over the living area surrounded by 2"x2"s at the overhangs with OSB over that. The foam itself is just laid in place. Pan Abode supplies 3 1/2" nails to secure the OSB through the insulation into the t&g decking. If you want to increase the depth of the foam your best bet is to stick with the same method they use: Add another layer of foam, increase the depth of the framing surrounding it to match the new foam thickness and secure the OSB, plywood or wood skip sheathing with long screws into the decking. Unfortunately, unlike the nails originally supplied, long screws are expensive.
Gentlemen,
Thank you both very much for your replies. They were both helpful and prompt.
Malcolm, our Panabode was build in the late 1970's and we use it as a three season cottage. My primary goal is to move to a metal roof, rather than shingles. One concern I have regarding the metal roof is noise transmission. We already hear rain on the roof and I am concerned that it may well get worse with metal roofing. Do you have any advice on that front?
No noise problem when metal roofing is installed on underlayment /
slip-sheet -- it sounds almost exactly the same as the shingles.
The noise concern comes from metal roofs with *nothing* under them
aside from the covered space and a few battens, but people seem unable
to make the distinction in their minds. When the roofing is sitting
on a solid substrate, it can't clang and resonate.
_H*
Barney,
A few years ago I replaced the original shingle roof with a metal one on a cabin at a resort built before Pan Abode began including foam over their decking. They then began to have complaints from guests about the noise when it rained. The next one I did was on one with foam and it is very quiet. As Hobbit says, the key is not having any void below the roofing and something like foam to dampen the structure borne sound.
http://www.pointnopointresort.com/room/cabin-11-graces-log-cabin/
Thanks Hobbit & Malcolm. I never imagined that I would get quality advice so quickly.
Malcolm, the Panabode cabins at Point-No-Point are very nice. We just refinished the exterior of ours. They are a lot of work, but beautiful cabins.
Regarding fastening the OSB through the foam and into the t&g, what spacing do you recommend?
Secondly, do you cover the OSB with ice & water shield before putting the metal roofing on as added insurance against the shallow pitch of the Panabode roof?
Barney,
They are great cabins for resorts, as compared to drywall units they take the abuse guests mete out a lot better.
Even though the OSB will be fully supported by the foam, I'd still stick to the code mandated 6" at the vertical joints between sheets and 12" in the field.
The pan abodes I've built were all at least 3 in 12 roofs, which in this climate don't need anything more than conventional underlayment.
Malcolm,
Thanks so much for the very helpful advice. I now feel very comfortable undertaking the replacement of the roofing on my Panabode cabin.
Good luck and enjoy the cabin. We are in for a hot summer here in BC!