Flooring and Coating System Requirements and Moisture Limits
Product-specific limits
Flooring and coating requirements come from the manufacturer's written data, not from a universal number. Many resilient-flooring adhesives specify 75–80% RH or 3–5 lb MVER, but epoxy, polyurethane, and cementitious coatings may allow different values. The specification can require both an RH and an MVER limit; both must be satisfied. Always verify the current data sheet for the specific product and application.
Why systems fail
Water vapor can re-emulsify adhesive, cause coating blistering, produce osmotic cells, or create disbondment at the primer. A coating with low permeance can trap vapor and magnify damage. Surface preparation, primer selection, and dew point during application also affect performance. Moisture-related failures often appear at perimeter areas or over vapor-retarder discontinuities.
Worked example
A product data sheet states ≤80% RH and ≤3 lb/1000 ft²/24 h. The slab tests at 2.5 lb MVER but 85% RH. The MVER passes, yet the system fails the RH limit. The correct conclusion is that the slab is not acceptable for that product; a moisture-vapor-reduction coating or longer drying may be needed, and the manufacturer should be consulted.
Traps
Do not apply one adhesive limit to every coating. Do not ignore the and in a dual limit. Do not assume a primer solves a failing slab unless the system is designed and warranted for it. Do not test only after covering the slab.