On Tue, 30 Dec 2008 23:17:14 +0000
(D.M. Procida) wrote:

This may turn out to be a stupid question, but I have nothing to
prove...

I don't understand why it isn't possible to make roofs cheaply, using
board materials instead of tiles or glass fibre. It's possible to make
boats waterproof, with appropriate sealing materials and pain, so why
not roofs, which have to deal with a lot less water?

It would be convenient and cheap to put large plywood boards on a roof,
make sure that there's some kind of overlap or flexible seal where their
edges meet, and finish them with thoroughly waterproof paint.

I'm assuming that I'm not a genius who has thought of something that has
never occurred to anyone else, and there is a reason why this isn't done
- what is it?

Daniele

I remember watching a (Norm Abrams) American program once where they
built an entire house with stressed-skin panels. Each prefab wall and
roof panel was plywood-skinned over a foam core edged with timber. They
were bolted together, and down to the foundations. The panels were
huge, so the constructors used a large mobile crane, but the basic
structure only took a few hours to do.

The roof was pre-covered with felt shingles, IIRC.

I've used light stressed-skin panels in constructions and they are
excellent in all respects. I would think a 12mm plywood skin over a
150mm core will easily carry a couple of guys jumping up and down - and
you get 150mm of foam insulation thrown in.

R.