A garage roof is usually a typical construction of Sterling board and tar. Older tar constructions will or may have stone on them or a silver coating which is supposed to be re-coated every few years.
Quite common are the concrete pre fab garages with asbestos roofs. As long as the asbestos roof is removed taking the correct procedures it can be disposed of quite easily.
We have undertaken quite a few of these pre fab constructions now whereas the roof is rebuilt in between the concrete structure with a made to measure timber and EPDM rubber surface.
Rubber Roofs 4 u can undertake these projects all over the UK turning an old garage which you cannot use into a useable garage where storage or vehicles can be kept.