On 14/06/2021 11:32, Andy Burns wrote:
Dave Plowman wrote:

Andy Burns wrote:

if it's been felted before, it'll have asphalt on the deck, which
"nothing" sticks to, and it's difficult to get it off completely.

Thanks, Andy. Since I'll almost certainly be going to glass fibre, does
the same apply?

I suppose I should have said bitumen rather than asphalt, but I dunno
whether resin would stick to it any better, if the chaps says new
decking is required, I'd tend to accept that.

When I EDPM'ed my roof the deck was soggy weetabix anyway, so got replaced.

With fibreglass it is even more important for all ply/OSB edges to be
supported. This means either using 18mm T&G OSB 8x2 decking or
supporting *all* butt joints with noggins.