A friend had a problem with damp in his garage, and had to leave the doors open all the time. It sounds similar. When he built his garage there was no damp course built into the floor and lower walls and so the moisture from the ground came through the concrete into the garage. If this is your problem, then you need to let the air flow through the garage to get rid of the moisture. The only other option it to rebuild the whole structure but put a damp course in. Not really an option!
Middlydiddly
April 2007