It depends on the material you use, but if your flat roof is installed correctly it should last for at least 10 years, and at least 20 if a material other than felt is used. Always question a roofing company when they quote to find out what materials they use and what guarantee's they offer.
Isle Of Scalpay
Scalpay is an island in the Outer Hebrides of Scotland. Scalpay is around 4 kilometres (2.5 miles) long and also rises to a height of 104 metres (341 feet) at Beinn Scorabhaig. The area of Scalpay is 653 hectares (2.52 sq mi). The primary settlement on the island is at the north, near the bridge, gathered around An Acairseid a Tuath (North Harbour). The island is peppered with small lochans. The largest of these is Loch an Duin (Loch of the Fort) which has a small island in it, with the remains of the fort still noticeable. Eilean Glas, a small peninsula on Scalpay's eastern shore, is house to the very first lighthouse to be integrated in the Outer Hebrides. Scalpay's nearby neighbour, Harris, is just 300 metres (980 feet) away across the tightens of Caolas Scalpaigh. In 1997, a bridge from Harris to Scalpay was developed, changing a ferry service. In 2001, the island had 322 individuals, whose main employment was fish farming as well as prawn fishing. By 2011 the population had decreased by 9% to 291 whilst throughout the very same period Scottish island populations overall grew by 4% to 103,702.