Many houses that were built in the twentieth century have a flat roof on some part of the property usually on extensions and garages because it was less expensive to erect a flat roof than a pitched one, so what if any are the implications of changing a flat roof to a pitched roof?As long as the flat roof is well constructed and the roofing material that has been used is of good quality then there should be no major issues for up to ten years however most people find that older flat roofs begin to leak as the roofing material deteriorates over time. Special rubberised roof coverings can be used however that are guaranteed for up to twenty-five years, but they are quite costly.The main advantage of a pitched roof is that once constructed it could be trouble free for far longer than a flat roof and will not usually need further attention unless any roof tiles are lost. Another advantage is that an internal loft space is created which can be utilised for extra storage.A pitched roof on an extension is more aesthetically pleasing because it looks as if the extended portion of the property was built with the original house rather than added at a later date.