Our house was originally a carpenter's workshop and my office was the old machine room in the cellar.
Unfortunately, when we had the room converted we ended-up with a cowboy builder who bodged the job.
He used the wrong materials, left no ventilation around the concrete ceiling, so condensation built up and we got damp in the roof.
So now we have had the old ceiling removed and a new one will be installed soon, after we have dried out.
As for the cowboy builder, he buggered off on his horse, with my money.