Test Method Selection, Scheduling, and Site Conditions
Selecting the method
Choose the test that matches the specified acceptance criterion. If the floor product has an RH limit, use ASTM F2170. If it has an MVER limit, use ASTM F1869. Some specifications require both because they describe different quantities. Surface methods (F2420, F2659) are for screening or diagnosis unless the specification explicitly allows them.
Scheduling and site conditions
- Test after the concrete has had time to cure and dry; do not schedule by calendar alone.
- Maintain the building at normal service temperature and humidity for at least 48–72 hours before and during testing; F1869 has its own tighter conditioning requirement.
- Keep the area clean, dry, and free of standing water; avoid direct sunlight, drafts, and localized heating.
- Record slab thickness, drying direction, vapor retarder, curing method, and HVAC status.
Worked example
A 150 mm slab-on-grade must receive flooring with a limit of 80% RH. The schedule allows 60 days of drying, then HVAC at service conditions for 72 hours. F2170 holes are drilled to 60 mm, and probes equilibrate 72 hours. If the slab is tested at 30 days in an unconditioned building, the result may be higher and not representative of service conditions; the test is premature.
Traps
Testing too early, testing before HVAC stabilization, or selecting F1869 because it is familiar when the spec is in RH are common failures. Do not test through standing water or after the floor covering is installed.