How can I make my garage less damp?

We have such a garage in the rented property we live in currently and if yours is like ours the only way to eradicate the damp is to build a new garage! You could spend thousands in trying to overcome this and not get anywhere.

Nope nope nope to that last answer! It's all about starting with the cheapest solution an eliminating problems never ever "knock it down start again"! Pressure wash the moss off with an anti-fungal water additive, then wait for the wall to dry out a bit. When that's done paint it either with and external paint (A good quality like a Fortress paint) or with a clear ant fungal paint, google a company called Twistfix they do such paint and we buy them from there, it's incredible stuff. When you've done that, time to treat the inside. Without looking at it, I can tell you garage has no DPC which says rising damp to me. Injection DPC to the rescue here, Twistfix do this but are quite expensive. I can recommend their stuff though as I've used it all. After that see if the floor stays damp, and consider building a second skin inside the garage. If it is the roof I will warn you only once Asbestos is BAD, being a husband of a nurse who treats patients who didn't listen to the warnings, I assure you it's long term lethal, a slow and painful death! So find a professional to get rid of it, councils are really clamping down on asbestos removal now (rightfully so!). Hope this helps, get in touch if you need me Kyle