First of all...although I'm in the North (Auburn, Washington), it doesn't get all that cold here. More often than not, it doesn't get below +20.
Here's my garage:
It's detached, uninsulated, and only the 2 stalls on the left are concrete. The far stall is crushed rock. Why? Well, the original builder (after all, it WAS a carport) set that stall up to park his boat in. Nice for a boats and carports...not so nice for cars and garages. At least the doors are facing AWAY from the weather.
Now I know that I need to get that floor completely slabbed, but until then I'm dealing with it. I have a 23,000 btu radiant kerosene heater (not one of those torpedo looking blasters) that I use for heat, and I've installed a ceiling fan to move the air around. The heater looks like this:
When I'm going out to work on something, I'll usually go out and turn them both on an hour or so before I feel like I want to be working.
As far as moisture and condensation goes, I do get very slight tool rust going if I'm not careful, but it doesn't seem to be related to when I use the garage heater. I believe it's mostly due to parking wet cars in there when you drive in out of the rain. I don't see any increase because of the heater. Maybe it's because the kerosene heater is a giant, circular, convection variety, it's not blowing air, so it doesn't heat the air faster than everything in it?
The garage has lots of those little screened air vents around the top (about every other stud I believe.) Should I be blocking those off? They were put there when it was a carport design you know...
Any thoughts on my interim setup?
What can you do about actually using your garage to park rain-soaked vehicles in it?