We get called in when a homebuyer's surveyor has circled the roof section in red. The good news: most 'serious' findings are routine repairs, and fixing them before exchange is almost always cheaper than the price reduction the buyer asks for.
The five we see most: slipped and missing tiles (usually a few hundred pounds); perished flat-roof felt on extensions (the biggest single cause of post-survey renegotiation); chimney stacks with open joints or a lean; moss so heavy it reads as 'roof at end of life'; and old cement-bonded asbestos garage roofs.
Our advice: get a drone survey before you list, not after the offer. £149 spent early usually saves thousands in renegotiation.