GB wrote:
I see them all the time - flat roofs that are completely level, and water
pools on the roof just waiting to get into the building. Why don't they get
built with a slight slope, maybe 1-2cms per metre? If that were done, the
worst of the water would run off rather than pooling and the roof would dry
out quickly once the rain stops.

Of course, that's harder to build, but how much harder? Is the main issue
packing out the joists so the roof slopes, or is there more to it than that?



I suspect because like my carpenters, the principles of trigonometry
escape them. They insisted on laying out the rafters for the 57 degree
pitched roof on the ground, and not trusting to sins coses and tans...

Bill: ere, how come this sheet of ply don't fit?
Alf: I told you that it doesn't work if it ain't flat.
Bill: so why dont we make it a bit bigger?
Alf: oh YES, but how MUCH bigger eh? That's rocket science, that is.
Trigernomettry. Not carpentry.