[dBlast]

You should wait at least one year before you do anything in the basement. If there are any leaks related to the builder's error it should be caught within the first year. I have had 2 new houses with walkout basements and both had minor leaks because the builder forgot to seal something properly. (e.g. the sliding patio door out the basement wasn't sealed properly and water was seeping into the basement)

It takes about a year for the concrete slab to dry fully. To test it, duck tape a 2 foot square of clear plastic to the slab, if there is moisture under the plastic after a few days it is still too wet to build or cover it.