Yeah, now you're talking.
An engineer or plumber with good troubleshooting skills can handle that.
Classic troubleshooting involves "divide and conquer"
Have you ruled out rainwater as your source?
Does the wetness stop if you shut off the water pressure?
How about if you just shut off the HOT water, at the hot water tank?
(Don't forget to alleviate pressure by opening faucets to relieve any valve
leakage.)
Could the wetness be arising from waste water?
Where are you located?

wrote in message
oups.com...
You might try turning off supply to each fixture and monitoring leak.
If you don't have time for that, cutting holes in the boards is the
only answer.
A Forensic Engineer or Architect might have equipment needed to look
through a relatively small hole.

Tom Baker