[Philip Fisher]

One other point on damp. Our detached garage was very damp when we moved in and there was mould on the back of the wooden up and over doors. I installed vents in all the soffits as there were no air vents. The garage was immediately far far better and now 15 years later we have never had a problem with damp or mould. It just needs airflow.

Soffit vents are simple to fit. You just need a circular hole saw and the round plastic vents just clip in the hole created. Just don't accidently try and cut a hole where there is a beam......