Determine manufacturer moisture-testing rules before installing finish flooring over a Gyp-Crete (gypsum concrete) underlayment

Steps

1. Identify the specific gypsum underlayment product (e.g., Gyp-Crete Basic, Gyp-Crete Radiant) since moisture limits are manufacturer- and product-specific
2. Note that manufacturer technical data sheets commonly specify a moisture content ceiling (e.g., not exceeding roughly 5% by an electronic/non-destructive method per ASTM F2659) for thinner pours, and reference ASTM F2170 in-situ RH testing (with a stated RH ceiling around 80% in some manufacturer literature) for thicker pours — treat these as manufacturer-specific figures to confirm on the current product data sheet, not universal constants
3. Confirm drying time expectations are conditions-dependent: manufacturer literature describes roughly 5-7 days under good ventilation/low humidity but notes drying can extend significantly longer without mechanical ventilation/dehumidification
4. Recommend the general contractor provide mechanical ventilation and heat as needed to accelerate drying if the schedule is tight, per manufacturer installation instructions
5. Confirm the finish flooring manufacturer's own moisture requirements are also satisfied — the underlayment manufacturer's pass criteria and the flooring manufacturer's pass criteria can differ and both must be met