But you’re still going to have 2" PVC rafters spanning > 15 ft. They are not going to be rigid enough to support the roof. They won’t even support their own weight without sagging. Why not build this the way your house is built?
My thinking is that the many fittings along the span will prevent the pipe from sagging and be able to support the roof. Schedule 80 pipe and fittings are very rigid. If there is sagging, the great thing about PVC is that I’ll be able to add studs without too much trouble.
The house was built with steel framing and a light weight concrete type panel system. Its expensive and difficult to get the materials to Hawaii. The pipe and fittings are more readily available.
Two inch PVC, with our without fittings, is not going to be anywhere near as rigid as a 2x8, which is what you would use for that span. And you have no interior walls to help support the roof-- you only have perimeter walls.
Yes, I’ve got to cut it back to a 10 foot span on the ends with 5 foot spans on the sides. I’ve just got to be able to drive my tractor through it.
I’d use aluminum studs and rafters. They’re not that expensive.