Is it detached or part of the house?

Is it detached or part of the house?

It's detached from the house, but attached to next door's garage.

The standard answer for this is usually ventilation.

Do you know where the moisture is coming from that is condensing? Eg are bikes put away wet, or is there damp coming through walls or the floor? I would possibly look at addressing this if so.

Setting a dehumidifier or heater going in a garage like this could be expensive, especially if it continually gets damp from some external factors.

Single skin brick?

Need to line the inside first with something waterproof. Dehumidifier will actually remove the water from the air, probably cheaper to run than a heater.

Do you know where the moisture is coming from that is condensing? Eg are bikes put away wet, or is there damp coming through walls or the floor? I would possibly look at addressing this if so

I think it's moisture from the air - no other obvious source. How could we improve the ventilation?

Single skin brick?

Single skin brick/block, but walls are sealed and don't seem damp.

We had a similar problem. I found that water was coming in under the door when it rained a lot; not loads, but just sort of seeping in along the surface of the concrete. I fitted a rubber garage door seal to the floor at the bottom of the door which stopped that pretty much completely, garage has been a lot drier since.

Ventilation is key though.

Desiccant dehumidifier for a garage. I can recommend the meaco zambezi or their standard dd8l if you don't want all the bells. Also a length hose to the outside if you don't want to be constantly emptying the tank.

+1 for desiccant dehumidifier. Sorted out my garage in very similar circumstances. Definitely get a hose to exterior.

APF

Humidifier with an external hose. A heater is just burning cash.

A dehumidifier will heat the garage while it runs, they're about 200% efficient.

We found the issue of damp from a neighbour who built his patio 2 bricks above the DPM. When he left the new neighbour let me cut through the slabs, dig out the soil ( which the previous owner said he had put drainage in ) and then damp seal the bricks to 2 bricks above the slabs. I then back filled with 20mm gravel and has dried out the walls. Just saying to check there is nothing like this thats an issue. I also have rubber edge on the doors as the wind used to blow the rain into the garage. Also boarded the loft area, so making the are smaller to then run a dehumidifier. Its on a humidistat , so only runs when needed and still manage about 4 ltrs a day in the damp times, but is a double garage which we go in and out a lot with dogs and bikes.

I have a dessicant dehumidifier which I move between the garage and the upstairs and downstairs of the house.

It's made a massive difference to the garage and has also made the house feel more pleasant and nipped a mold problem in the bud.

Just running it a few times a week in the garage does the job. Also seems to benefit my bikes as it dries them off properly after a wash.