How much would the materials cost to refelt an L-shaped dormer roof using quality materials and underfelt. To be laid on top of existing felt. External measurement of L-shape is app 7m x 5m and dormers are app 2m from front to back. I guess about 20m of felt, could need three rolls plus a similar amount of under felt.
Google EPDM flat roof, Johnny. Plenty of suppliers online ... with materials prices.
They often have traditional "hot pitch" type materials as well, but EPDM is the favourite these days for DIY.