You do building work don't you? .. error, yes I do stuff. Could you have a look at my garden room, it's feeling damp and smells fusty.

Apparently built and roofed around 10 years ago by a local builder - ledger board and dot and dab directly onto a retaining wall so ledger is rotten, PB is soaking wet and the concrete base goes right against the wall so nowhere for water to escape except under the flooring.