Well, the radiant heating guy came over several days ago with our hardwood floor contractor. After an extensive review, he determined our old radiant heating system WAS shut down correctly. It is not the source of our wet slab. He did, however, get up on our roof and make a discovery. It appears that there was a standing puddle of water at a joint area on our roof. This happens to be right over the most wet area of our floor. The new assumption is that the roof (which was replaced about 3 years ago) is leaking in this joint area, and running a trickle of water down BETWEEN the walls where it hits the slab and fans out. Interestingly enough, the percentage of water under our floor increases when it rains...lending credibility to the roof hypothesis. Next step is to have a roofer come over and inspect.
Questions: I looked into my homeowners insurance policy. Turns out water damage is difficult to claim. How can I position this to get it covered? Secondly, any ideas if roofers guarantee their work? We're having our real estate agent contact the sellers to see if we can learn more about the roofer and who's responsibility this is. Any thoughts would be appreciated!