I live in a wood frame house built circa 1940 (coastal California). It was pouring rain this morning and I got a call at work from my daughter that there was water coming through the ceiling. I went home and opened up the attic and found a pretty good leak from the area around the valley. For now, I put a container under it, and am running a fan to dry it out.

But I realize I need a new roof. I always figured that when I do replace the roof, I would do it right and insulate it and extend the overhangs. Currently there is no insulation and no overhangs. The house was originally built as one story with a 12:12 roof. In 1952, the attic was finished to create some additional bedrooms. The footprint is about 1000 sq. ft. Gyp board was applied to the bottom of the roof rafters in the finished area of the attic. The 2x4 roof rafters sit on the exterior walls with no overhang and there is 1x decking, not skipped.

I would like some opinions about how to go about re-roofing. I considered SIPS, but there would be no access for a crane, so getting them on the roof my pose a problem. And there are 4 valleys and 3 skylights to work around.

Another option would be to remove the existing shingles and have foam insulation injected into each bay and spray the bottom of the roof in the areas that are just attic. That would solve the problem of insulation, but not extending the overhangs.

I could also apply plywood on top of the existing decking, then install stringers that would cantilever past the exterior walls to create the overhang. Rigid insulation would go between the 2x stringers and plywood over the top. I would top it all off with heavy composition shingles.

Most of the roof is not vented, since they applied gyp board to the bottom of the roof rafters and the remaining spaces behind the knee walls were not vented. This doesn't seem to be a problem since there is no insulation and the indoor humidity is not an issue.

Any thoughts on the subject? Or any other suggestions for achieving a similar end result?

I appreciate all the ideas that people take the time and effort to post on this forum. The combined experience of the members is phenomenal.

Hunter, Atlas et al sell 4x8 sheets of iso insulation with nailer-deck already applied, which would likely be both cheaper and more effective than foaming from the underside of the deck. Since the nailer is only one side you'd have to do a little some thing for the overhangs, but that shouldn't be a big deal. It'll be a lot less labor (and possibly less money) than doing it with EPS and a bunch of plywood. They're not very dense either- similar in heft to a sheet of 3/4" plywood- and can be manually hoisted up there. You'd have to long-screw them to the original roof deck, but that's easy & quick for panels 4" or thinner (use 5" screws with 4" panels to be mechanically secure.)

One advantage of putting the insulation above the original roof deck vs. foaming from below is that the rafters aren't thermally bridging through the insulation. R25 rigid-board above the roof deck outperforms R30 sprayed from below. An R25 iso with OSB nailer is about 4" thick. R20 panels are about 3.25" thick.

This is how I plant boost the R on my place when it's time to re-roof- been studying it for awhile. I'm also considering using them under siding for a high-R wall retrofit. They're basically half-SIP panels in 4x8' modules- half the Oreo with the cookie on one side only. Sealing the seams with tape/mastic/foam, whatever the manufacturer recommends makes them very high peroformance from an air infiltration point of view as well.