Having just about recovered from Whooping cough/Bronchitis I decided that I would extend and over roof the workshop leaving the existing roof in place. All went well, 50mm insulation sheets fitted, frames fitted around insulation,3/4" ply sheets fitted all screwed through to the original roof timbers. I got a friend to give a hand to fit battens and membrane and we then lifted the 16ft steel profiled sheets onto the roof for me to fix down which I duly did, leaving the front to be trimmed to the correct overhang before fitting facias. The intention is to have the edge of the sheets on both west and south sides built into the existing boundary walls which surround the workshop on those sides. I left the last sheet off until I,ve lifted the wall to correct height but the previous sheet overhangs by about 18" on the long edge. Today I marked off (from below) the required overhang before fitting facias and gutters and then climbed up onto the roof to mark the cut line from above before application of the 9" grinder. I carefully fixed a length of twine at one end and walked to the other end to tighten it to give the cut line. I FORGOT THE BL--DY UNSUPPORTED OVERHANG !! I fell 9ft missing the boundary wall with all except my right hand and landed on my back on the only rock I left out when rebuilding the wall.Ribs on right rear all severely bruised,right hand deep gashes but thankfully no back/head injury or breakages. Looks like I,m out of commision for a while as I can,t lift anything or breath without pain. OLD FOOL!!