On Sun, 26 Jul 2020 14:07:41 +0100, Fredxx wrote:

EPDM seem all the rage.
https://en.wikipedia.org/wiki/Flat_roof#EPDM

Had ours fibre glassed about 10 years ago. New OSB boards, the old
torch-on felt had failed and knackered those boards. Took the
oportunity to fit 100 mm of celotext between the roof joists. The
fibre glass is still waterproof or at least if it is leaking it's not
getting to anywhere visible inside. But then there is a poly sheet on
the warm side of the insulation and up and over the joists...

--
Cheers
Dave.