Am elderly friend of a friend has a lean-to shed at the back of her house, the roof of which made (many years ago) from corrugated asbestos sheet. The roof has started to leak and she's thinking in terms of getting it replaced.
Obviously, removal of the old roof would require specialised contractors and considerable expense. Is there anything that could be painted (or sprayed) onto the roof that would form a waterproof barrier to extend the life of the roof until after the house owner has moved or died?