waterproofing a garage? how?

[V]

ok, i need to figure out how to waterproof my garage, water leaks in through the ceiling and always makes a puddle right in the middle. I want to store cars in there but im hesitant with it leaking. i know i could tarp stuff but thats the lame way out. The garage is about 22' deep and 14' wide. The ceiling is only about 7" high so its easy to reach. Now heres my problem, the ceiling is actually made up of several formed concrete slabs that are each about 2' wide and they run from the front to the back, all supported by steel I-beams. The water seems to be leaking in, right in the middle, at the seems along these concrete slabs. The roof of the garage is a deck, with a sprayed-on concrete design that was just done 5-6 years ago. Apparantly they never sealed the surface properly. We have had issues with them right after the job was done about other items and they are no longer in business so going back to them is impossible. SO, all that means ripping up the deck surface is not an option. I figure if i just spray some sealer in the seam it may stop it for a little while but it may trap water up there and eventually make the problem worse... What should i do? I can take pictures tomorrow.

[Savage_Messiah]

1) go to shoprite

2) buy all of their garbage bags and duct tape

3) lay all the garbage bags over your roof, apply tape

[j0n]

great stuff...located in the building materials section of home depot...hit any and all cracks with it and you're all set

[ShitOnWheels]

dry lock will also be an option, tho expensive. Waterproofs concrete pretty well. May need to fill the seams first tho.

[GP99GT]

maybe some driveway crack sealer? its like a rope thing, you lay it along the crack and hit it with a blowtorch, it melts into the crack and fills it, and hardens back up. if you can do it from the top, i think it would work. just put something underneath to catch in case some of it drips through