Standard
ASTM F2170-19a
Determines relative humidity inside a concrete slab with in situ probes. This is the test a slab has to pass before an epoxy topcoat goes down.
What it means for your floor
Why moisture decides the job
Water vapour moving up through a slab pushes against the underside of a coating. If the slab is too wet when the system goes down, the floor can debond later regardless of how well it was installed. This is the single most common reason a resinous floor fails early.
The numbers on this system
The manufacturer data behind New Era's published figures sets the slab limits at under 80 percent internal relative humidity under F2170, and 8 to 10 lbs per 1,000 sq ft per 24 hours of vapour emission under the older F1869 calcium chloride test.
In situ, not surface
F2170 reads humidity inside the slab through drilled probes, which is why it supplanted surface tests. A slab can read dry on top and hold plenty of moisture at depth.