Reroof and insulation of low pitch roof
I have a 1950’s post and beam house. The roof is 4X12- 8’o.c. with 2X6 toungue and groove decking. On top of that is 1″ celotex type material with tar and gravel. The pitch is app. 1.5/12. Maybe 4 years ago the roof started to leak. I never liked the look of the gravel so my solution at that time was to scrape off the chunks of tar and lay down 1/2″Dow foamboard, 1/2″ plywood, felt, and corrugated steel. The roof does not leak into the house, but ants have moved into the celotex indicating moisture. I used silicone to seal the flashing and it looks to have failed in that environment.
I would like to strip off the whole bit down to the decking and start over. I want to end up with steel roofing and better insulation. Corrugated steel may seem like an odd choice , but it works with the architecture. One idea I am considering is to frame on top of the decking with 2 X4s on edge which would allow me to shim and compensate for a 3/4″-1″ sag in the roof. Then I am thinking of having two part polyurethane insulation sprayed between the framing and proceeding with 1/2″plywood, 30 lb felt and corrugated steel.
Comments on this approach or other suggestions would be greatly appreciated.
Replies
The poly spray insulation roof is the best solution and can do everything you need to do in one step. They can spray it in different thicknesses to compensate for dips where puddles used to form.
You should not have to do any additional framing or anything like that.
Start looking now, it might be hard to find a contractor in your area. And a small job might take a few calls to get it done.
Good luck!
Stu
Hi, My neighbor had poly insulation sprayed over the tar and gravel and I think it is hard to control the thickness because it expands so much. It looks like cake frosting. Also they sprayed some type of silver coating over the polyurethane insulation and it looks to be cracking. The reason I would like to frame over the t&g decking is to provide nailing for plywood and steel roofing as well as extra space for insulation. I believe they try and spray it at 1.25" when they just spray it on the foof deck. The R-value is around 6 /inch. Also, I would like to add ceiling light fixtures in this space (pendants, not cans).
I read some other posts about steel roofing on a low slope and some people have said it is not recommended for systems with exposed fasteners. I do have a phenomenon where the bottom row of screws at the eaves almost completely backs out every couple of years. The biggest problem is that the silicone caulk I used to seal the 3/8" waves in the metal roofing to flashing @ adjecent walls, chimney, roof jacks, etc., does not seem to be up to the task.
Thanks for your input.
chuck
It's possible that I'm not reading or "seeing" your description correctly. But I'm thinking its not a good idea to add anything on top until the sags are corrected. Either replace the 2X6 T&G where needed or sister the rafters.
Mark