Commercial Concrete Moisture Testing: Why It's Non-Negotiable Before Coating

The Test Most Often Skipped

Ask how the slab will be assessed for moisture and which acceptance limits apply to the selected products. Confirm whether mitigation is included before authorizing work.

Why On-Grade Slabs Are the Real Risk

Ask the independent provider to identify contaminants and exposure conditions, then explain preparation, product suitability, and any exclusions in the written scope.

The Two Standard Test Methods

• Ask how the slab will be assessed for moisture and which acceptance limits apply to the selected products. Confirm whether mitigation is included before authorizing work.
• Relative humidity (RH) probe testing measures moisture deeper within the slab using embedded probes, generally considered more representative of the slab's actual internal condition, and is increasingly the preferred method for commercial projects.

What the Results Actually Change

Readings within acceptable range for the coating system being used mean standard installation can proceed. Elevated readings don't necessarily mean coating is impossible — they usually mean a moisture-mitigating primer, rated for the specific vapor emission level measured, needs to go down first. Skipping that step on a slab with elevated readings is exactly what leads to bubbling and delamination months or years later.

Why This Should Never Be an Afterthought

A legitimate commercial flooring contractor tests before quoting a final price, not after installation problems appear — because the results can change which primer, and sometimes which overall system, is appropriate. If a contractor's estimate doesn't mention moisture testing at all, that's worth asking about directly.

Frequently Asked Questions