How would you go about extending a dormer type house IE,flat roofs above upatair rooms front and back.I do not really want any more flat roofs.I want to extend to the rear the full width of my existing building.The dormers do not go the the edge of my house,there is around 2 tiles width of conventional roofing either side.I can mail a photo to anyone with ideas,or willing to offer advice,thanks in anticipation.