project description. fibreglass / grp roofing. home | roofing | roof repairs | chimney repairs | chimney lining | moss removal | contact us. the dry valley is fitted onto the valley boards and firmly fixed from the eaves closure section upwards using large headed roofing nails, fix the trouugh . grp fibreglass flat roof to a side extension in lowedges sheffield. coolock fibreglass flat roof extension 3. a fibreglass roof covering of 1 layer of 450gm mat plus a coating of fire retardant dark grey topcoat these kits can be used by the professional roofer .