What depth do I drill to measure when pouring new concrete on an old slab?

Please Note: This is somewhat out of the norm and is not covered by the ASTM F2170 standard. The following answer is based on information we have received from experts.

Example:

A 5-year-old existing 4-inch slab has 3-inches of new cement. The total thickness is 7-inches.

The test hole should be drilled at 40% depth of combined thickness (7-inches) unless there is a vapor barrier between the two slabs. If there is a vapor barrier then the test hole should be drilled at 40% depth of 3-inches.

The same information applies to precast slabs.

Please visit Measuring RH at Correct Depth is Critical and Performing Correct and Accurate RH Testing

The following two tabs change content below.
Wagner Meters is a family-owned American business that aims to provide solutions in moisture measurement technology that will enhance the quality and value of each customer's project. With an almost 60-year legacy of innovation, Wagner continues to be a resource for both individual craftsmen and high-performance commercial endeavors.