I am re-roofing 200 +/- yr old TF 1-3/4 sty ell of my house. Total roof area is 400 sf, 5/12 pitch, has 3 bents, (end, midway & one against main house)& horiz. purlins 32" oc.
Plan to cover framing with 5/4 t&g or splined white pine, inside planed and beaded for ceiling. Then rigid foam, "tuff-r" two 2" layers, removing vapor barrier in middle and staggering & taping joints. Then 5/8 exterior ply wood covered with ice & water shield. This will be covered with "cedar breather" mat and white cedar shingles with ridge vent.

I have no experience doing this. Will the foam support a snow load? The foam comes with vapor barriers on both sides, is this the way to go? Would greatly appreciate any advice on methods and or products. Thank you

the foam will be fine as long as your t&g is strong enough. 5/4 on 32" centers may be a bit light....

Hi Cjay,

have you gotten anywhere with your roof yet?
5/4 t&g should be alright but I would go with 1.5" t&g.
On top of that you should install a vapor barrier since you will not be able to tape seams on the side of the insulation facing the warm side of the roof. After installing all your insulation foam gaps and tape all seams. This way it will shed water if it did start raining before the roof is finished and also if the roof would leak or has condensation underneath the cedar. Now instead of fastening plywood to the insulation run 2x4s vertically(from soffit to ridge) every 24"O.C. screwed into the purlins. On top of that run 2x3s( 1x3 furring strips should do but feel spongy) every 5" or what ever the exposure for your cedar is. I would not use the "cedar breather" nonsense.It is too thin a layer to be effective for ventilation on top of the fact that there is a lot of material(mesh)for the air to go through which will slow the circulation. Hope this helps some. Search also for Rigid foam roof installation. There have been some postings about similar scenarios.