2.5mm single chamber fluted polyboard for placing under your final roof finish that acts as an insulated membrane (similar to the fluted polycarbonate sheeting on conservatory roofs). Also acts as a quick method of weather protection, although it will not be 100% waterproof as sometimes the material will just cover the width of the roof area as dictated by the purlins/rafters. Sheets of material measure approximately 2500mm long x 1200mm wide, flutes run in the long direction.
Place the membrane on the roof with the flutes running up it, and trim to suit. Some sheets may need to be cut and trimmed to suit the overall length of the boards. Hold in place, put the final roof finish on top, and nail through. Extra nails are not supplied with this material.