I have a flat roof to do, its very old and the felt is brittle. It's got the loose gravel on the top and about 2 inches of moss all over it. I have cleared the moss but rain water still seems to pool in certain areas, very small pools and only a couple, is this normal. Also before I apply a new felt which has to be blow torched on the underside to stick to the existing old felt, how dry does the surface have to be, I've been told that if its damp and the excess water is swept off there shouldn't be a problem, also apparently there are other products out there which can be used specifically in damp weather. Any advice would be appreciated. Thanks, Roo
You need to remove 100% of moss and "any loose" gravel.
Water will pool on flat roofs, so long as it don't pool longer than 48 hours it's pretty normal, over 72 hours is really bad.
The surface of the existing roof needs to be 100% dry.
If it's damp/wet when you are trying to get started you can use a broom to push the bulk off than use a cotton "string" mop to suck up the remaining puddles and than run your torch across the surface in quick motions to dry up the rest.
Run the torch 30 seconds to long in anyone spot and you overheat the new product which will turn into blisters in the near future, 30 seconds not long enough and you won't get full adhesion.
Either will result in premature failure.
If you can't afford to hire a roofing contractor than hire a roofer,
you supply materials and labor and let him/her supply experience.