My timber mancave which has a felt roof I have just discovered the felt seems to be porous as the plywood deck is permanently damp and showing signs of rot.
it is a shallow slope so am looking for a felt alternate covering to do it myself in the spring
what is available out there

How much fall is on the roof?

Fibreglass?

Fall about 40cm over 4 metres

Edit
just measured it with the iphone spirit level thingy and it says 4 degrees slope

EPDM rubber roof cut to size + 6″ all round , few tins spray adhesives and away you go , done all my sheds and detached garage over the last few years and all been spot on, top tip ,ask neighbors to move car before going mad with spray adhesive unless of course you don’t like them!!!!

That EPDM rubber looks like the favorite for ease of fitting on an awkward shape
Thanks Mainman