On Wed, 20 Jul 2011 19:51:54 +0100, "Phil L"
wrote:


'flat' rooves are not flat, they already have this slope built into them,
and no, it's not hard to do, it's a taper - timber merchants will cut any
sized taper you want, up to 6m in length - these are placed one upon each
joist to achieve the fall.

What my builder did last year. But the flat roof built on my dad's
extension c1963 was truly flat; with roofing felt hot tarred on and
solar chippings it was not very good but probably typical of the time.