A properly laid fibreglass roof also known as GRP Roofing, will last for at least 30 years with no measurable deterioration. The roof must be laid onto a dry deck in dry conditions at a temperature not below 5°C. The resin and top coat should be suitable for use in GRP Roofing. This guide relates only to the application of the GRP laminate and top coat. The deck should be of 18 mm exterior plywood or Sterling Board and be well fixed to the underlying joists. Typically two men can strip, re-deck, laminate and top coat a roof of about 20 square metres in one day. Always try to plan starting the roof when a settled period of weather is forecast. The deck may be a new deck, or may be formed over an existing roof. You should ensure that the new deck is laid to adequate falls in order to allow good drainage, so that there is no standing water on the roof after completion. 
Materials:
Once the new deck has been formed you will need the following.Resin: allow 1.5Kg/m2 for 450g glass or 2 Kg/m2 for 600g glass.Top coat: allow 0.5Kg/m2. Glass: Emulsion bound chopped strand mat (CSM). The minimum should be a single layer of 450gm or for a heavier laminate a single layer of 600gm mat.