Concrete is a permeable substance capable of absorbing and releasing moisture, which can continue to affect the RH (relative humidity) of a slab long after it has been placed. Groundwater, high humidity and leaking plumbing are the top causes of moisture problems in a concrete slab.
Many people don't realise how important moisture testing is with concrete subfloors, especially with old concrete. After all, if the slab was poured 10 years ago, it must be dry, right? Furthermore, if it had a floor installed for that time, there can't be a problem, right?
Maybe. Maybe not.
Flooring Magazine Publication Link - Page 62-63
