Using CC Foam on a Doublewide roof
I build cabinets to make a living but feel dumb when it comes to home repair or remodling. I talk with different proffesionals everyday and get twice as many opinions on how to do something.
I’ve got a doublewide that has no access to the attic area, plus a lot of it has vaulted ceilings so there is no room up there to start with. When I reroofed this place a few years ago I had to replace some of the decking. I noticed that the insulation in the ceiling was next to nothing but didn’t do anything about it at that time. Years later after a lot of high utility bills I have decided to insulate the roof. After talking with different contractors the best way to do this for the best performance was to use closed cell foam. Their idear is to use 2 x 4s on top of my shingles with the 3 1/2 side standing up and build a frame work on top of the roof, then spray the foam between the 2 x 4s directly on top of the shingles and then I plan to top that with a metal roof. Has anyone seen this done before or do you think I’am wasting my money? Would appreciate any comments.
Replies
Don't use
spray foam for that, use rigid foam board in 4x8 sheets. You do not need the 2x4 grid. Remove the existing roofing down to the wood deck or whatever sheathing is there, lay down foam board over, screw or nail it a little bit to keep it in place, then lay 1x4s across the roof over the foam at 24" o.c. and attach it with lonnnnng screws. Then screw the metal to the 1x4. Probably want a layer of felt over the foam. Think about how you will add fascia board to cover the edges.
If you decide to go with two layers of foam, stagger the seams.
Cellulose
I'd look at blowing in cellulose by removing coupons of the existing roof, and blowing most of the void full of cellulose or the loose fiberglass made for blowing.
Then put new sheating over the holes, install a good underlay vapor stop for the metal roof, and then install the metal.