How the Rapid RH System Tests Concrete Moisture

Updated

Wagner Meters' Rapid RH® system tests concrete moisture by measuring relative humidity (RH) inside a drilled hole at a specified depth, following the in-situ method described by ASTM F2170. You drill and clean a hole, seal in a Rapid RH sensor, let it equilibrate, then read the RH and temperature. The system comes in single-use (Rapid RH® L6) and reusable (Rapid RH® 5.0) sensor versions, with readings collected by a handheld reader or the DataGrabber® data logger.

What the test measures and why depth matters

A surface meter reads only the top layer of a slab, but moisture deeper in the slab can migrate upward after flooring is installed. In-situ testing places the sensor at a defined depth so the reading reflects the slab's internal humidity. ASTM F2170 is the standard Wagner references for this method, and the site provides an ASTM F2170 checklist and a concrete slab moisture testing spec you can hand to a project team.

The Rapid RH test sequence

The exact hole depth, number of holes, and equilibration time are set by the ASTM F2170 procedure and the project spec—confirm both before drilling. The general sequence:

  1. Prepare the hole. Drill to the specified depth, then clean the hole thoroughly. Dust left in the hole skews the reading.
  2. Seal and place the sensor. Insert the Rapid RH sensor and seal the hole so the sensor is isolated from ambient air.
  3. Let it equilibrate. Wait the period the standard and sensor instructions require before taking a reading.
  4. Read and record. Use the handheld reader or the DataGrabber® data logger to capture RH and temperature.
  5. Map the results. Log each reading against its location so the floor plan shows where the slab is wetter.

Single-use vs. reusable sensors

Rapid RH® L6 (single-use) Rapid RH® 5.0 (reusable)
Sensor Left in place after reading Retrieved and reused
Best for One-time verification, documented records Multiple projects or repeated checks
Trade-off No retrieval step Requires recovery and care between uses

Choose single-use when you want a permanent record in the slab; choose reusable when sensor cost across many jobs matters more than leaving sensors behind.

Resources that support the test

Wagner publishes a Rapid RH installation guide, a Rapid RH floor map, an ASTM F2170 checklist, and concrete moisture articles and videos. The floor map is the practical tool for tracking hole locations and readings across a large slab; the checklist keeps the sequence from being skipped.

Common pitfalls

  • Skipping hole cleaning. Dust and debris are a frequent cause of readings that don't match later floor performance.
  • Reading too early. Equilibration time is not optional; a rushed reading understates or overstates slab humidity.
  • Too few test locations. The standard and project spec define how many holes a slab needs—follow them rather than sampling one spot.
  • Confusing surface and in-situ results. A C555 concrete moisture meter and the Rapid RH in-situ test answer different questions; don't substitute one for the other in a flooring decision.

For product selection across concrete and wood, Wagner's "Which Product Is Right For You?" tool and its distributor locator are the next stops.