Hopefully one of the professionals here will have an answer for you. I had a similar problem this winter, to a much lesser degree which I solved with a dehumidifying exhaust vent ( http://wizzvent.com/products/wizzvent/). I was told the reason was because the garage was so tight and unheated, the extra humidity from the new construction couldn't escape.

Yours sounds more serious or maybe a different issue. I hope you find an answer. Good luck.

I presume that you have had your contractor back to ask him/her to fix it?

Ranicamp, is this an attached garage or detached? There could be a number of sources causing the moisture in your garage. It could be that you have some moisture in the slab itself being released in the garage. If you're working in the garage, you are a source of moisture.........the reason that this was not a problem before is that you had more circulation before you closed it up. Most garages are not air tight.

When you closed it in, you cut off all those leak areas that allowed the moisture to escape......added to that, you also created some temperature differentiation spaces. The air in your newly enclosed garage is warmer and carries more moisture in a confined space. The ceiling is a barrier between that space and the colder, dryer space behind the dry wall...........what happens when warm, moisture laden air comes in contact with a colder surface........................you get condensation.

There are a number of ways to solve this problem. A layer of insulation in the ceiling would have helped, but short of that, you can place a dehumidifier in the space or you can add an exhaust fan. In the summer when it gets dries and warmer, I suspect your condensation problem will lessen or be gone completely. If your concrete slab is bare concrete you might try at this time to seal it with one of the garage floor coating systems.........but the cheapest and quickest fix will be to get some means for the moisture in your garage a way of escaping........add an exhaust fan to your space..

Thanks everyone for all your advice, no I did not have my contractor back, because I was ticked off that he did not forsee this problem, had I know I would have left it unpainted...ahh well. S Thomas will try your solutions and see how that works. Thanks.

You should have the contractor back in right away.