Are you using the garage every day or for winter storage?
Fan on a timer for everyday or sealed garage and dehumidifier.

 

You could paint the whole lot with epoxy floor paint - you need to work fast. That will provide a barrier.

What's the roof like? Cracked asbestos sheet? Celotex lining will help.

Air bricks are also your friend.

 

Batten it out, line it with cellotex, then board it over, either plaster board or OSB. Floor with good old garage floor paint. If there's a persistent high humidity problem A good dehumidifier will work.
Alternatively get polythene car tent to go inside the garage. This - http://www.hamiltonclassic.co.uk/acatalog/info_4.html

 

Garage floor paint is shyte, a 2 pack epoxy will seal the floor and if you acid clean will stay stuck

Google regal paints, their stuff is excellent

The walls you can drill and inject damp proofing depending on the brick. Most garages are well ventilated round the doors and roof

 

Some good suggestions here, thanks all. There seems to be loads of products out there for dealing with damp so might get my neighbour (builder) in to give his 2p worth.


So far, I like the idea of using the Vandex with the possible option of Regal paint on the floor. I don't fancy battening and the inside tent idea wouldn't work - thanks though.


The detached garage is a 1950s brick wall and concrete floor construction with a pitched tiled roof; ventilation isn’t a problem. Some repair work is needed to the concrete floor as it’s been bodged in the past.

It’s a tight squeeze width wise but with plenty of length and would be used to protect the S2000 from the weather, cats, leaves, birds etc etc as well as for storage.

 

I have a single skinned garage but adopted a slightly different approach, based as much on aesthetics as damp prevention.

It is mostly block construction with the only attractive bits being brick piers at the front corners.

I battened the outside, attached a felt barrier and then fixed tongue and groove all round.

I'm very happy with the improved look but not convinced it does much in terms of damp.

I think the issue is low temperature and restricted airflow so I would say the only way to keep it damp free is better sealing (I am about to fit a roller door) heating and a dehumidifier.

 

Neat solution, Gad. Also you don't lose precious width, given the lardiness of modern rubbish.

I found that epoxying the (bad) floor and later laying the lino has made the garage feel a lot less damp. Since the garage is attached and has a boiler in it, it was not actually a problem before.

I think a lot of dampness rises through the concrete floor, as it is necessarily below the level of the DPC.

 

I have like many people a single course brick garage with flat felted roof. My solution is simple, an air vent in the wooden side door and the floor is carpeted with a rubber backed commercial grade carpet. This acts like a damp proof membrane...as has been said above a lot of the damp comes through the base.
Does this work ? in short yes ! I can leave my car in there for the winter and I get no damp, even after several weeks of no use the brake discs have no surface rust on them from damp air. Ventilation is the key.

 

Does that not mean it goes all mouldy under the carpet though as the damp gets trapped between floor and rubber from the carpet?

 

You'd only need to worry about the floor and the first metre of wall. Rising damp certainly won't go any higher than that.

Personally, i'd just paint the floor with a decent epoxy paint, improve the ventilation and put in a greenhouse type fan heater on a timer.

A lot of the damp will come in through the floor, improving the ventilation will mean the improved airflow will help carry away higher humidity air and a greenhouse fan heater will further improve the ventilation to avoid any damp spots and the addition of heat will help evaporate the dampness allowing it to be carried away by the improved airflow.