Short answers to the questions we hear most from owners, contractors, and restoration teams.
Start with the flooring and adhesive installation instructions: they say which test the moisture limit is based on. ASTM F2170 uses probes placed in drilled holes to measure relative humidity inside the slab and is the method most manufacturers now reference. ASTM F1869 (calcium chloride) measures moisture vapor coming off the prepared surface over a set exposure period. If the instructions list both, testing both gives the fullest picture.
Non-destructive meters are excellent for moisture mapping — finding wet and dry zones and deciding where to test. But their readings are comparative. They do not produce the RH or emission-rate numbers that flooring warranties are written against, so they don't replace F2170 or F1869 when those methods are specified.
The building should be at the temperature and humidity it will normally operate at before testing — HVAC running, windows and doors closed. Testing areas should be accessible and, for calcium chloride, bare and clean. Let us know about radiant heat, recent water events, sealers, or curing compounds.
First map the floor to see how far the water traveled. Then track drying with repeat readings. Before new flooring goes in, test with the method the new flooring requires. A surface that looks and feels dry can still hold moisture deeper in the slab.
Each result is compared to the written limit for the specific flooring and adhesive. Results apply to the tested locations at the time of testing. If a location is over the limit, options usually include more drying time, a moisture mitigation system, or a product rated for higher moisture — per the manufacturer.
Both ASTM F2170 and F1869 call for at least three tests for the first 1,000 sq ft, plus one more for each additional 1,000 sq ft. Our free calculator estimates the count for your slab area.
General information only. Always follow the flooring and adhesive manufacturer's written requirements and the full published ASTM procedures.