The Real Costs: Calcium Chloride (CaCl) vs. RH Testing

Calculator and Expense Record

For decades, flooring contractors have conducted moisture tests to verify the appropriate “dryness” of a concrete slab, prior to installing finished floor products. The anhydrous calcium chloride (CaCl) provided a moisture vapor emissions rate (MVER) which was the industry benchmark since the 1950s. In the 1990s, experts raised methodology concerns and suggested that the CaCl test did not indicate a thorough enough measure of concrete moisture content (MC). Since then, relative humidity (RH) testing has emerged as an alternative. Both tests may still be used, but many may ask: which one is best?

CaCl Test vs. RH: Materials

The first place most businesses would look to answer that question is cost. And cost alone would make it seem that CaCl comes out ahead. If contractors apply the CaCl test in 13 locations of a 10,000 square foot slab, they pay a materials cost of $147.95, or $11.38 per test. In the building business, the CaCl test may appear to be cost-effective.

Bottom Line Calcium Chloride (CaCl) Relative Humidity (RH)
Material Costs (13 tests) $147.95 $600.00

CaCl Test vs. RH: Time

But time equals money, too, and it is there that the anhydrous CaCl test becomes a heavyweight. If contractors place in-situ RH probes at 40% depth in 13 locations of a 10,000 square foot slab, they can obtain overall RH assessment in 94% less time than the anhydrous CaCl test. By deploying RH testing, contractors save 54.82 man hours of cost.

Test Task Calcium Chloride (CaCl) Relative Humidity (RH)
Prepare test locations 65 minutes 0 min.
Prepare the test 65 minutes 0 min.
Place the test 65 minutes 65 minutes
Protect the test 120 minutes 0 min.
Obtain results 130 minutes 3.5 minutes
Cleanup 20 minutes 7 minutes
Time Required (13 tests) 4,320 minutes (72 hrs.) 120 minutes (2 hrs.)
Total Test Time 3,495 minutes (158 hrs. 15 min.) 205.5 minutes (3 hrs. 25.5 min.)

Multiply the Savings

Contractors pay an extra $452.02 for an MC test based on RH, and they save 54.82 man hours for it. Further, the CaCl test measures moisture vapor emissions at the slab surface. It does not indicate MC levels or moisture migration through the concrete slab. Measured by both time and test integrity, RH concrete moisture testing appears to hold a long-term edge despite higher up-front costs.

What to do with 54.82 hours of your budget? Hire contractors! Here’s how long you could employ the following trades people based on the amount saved on moisture testing ($452.02) multiplied by their average national wage in 2011:

Job/Trade Time (Hrs.)
Surveyor 16.96
Civil Engineer 12.29
Construction Laborers 31.56
Environmental Engineer 12.92
Carpenter 21.54
Floor Layers 24.67
Concrete Finishers 26.2
Drywall/Tile Installers 24.29
Pipelayers 26.79

Source: US Bureau of Labor Statistics (Web).

In a constrained budgetary world, the RH test trumps the anhydrous CaCl test on both methodological and economic grounds. Concrete slabs and construction projects gain.


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Jason Spangler

Jason has 20+ years' experience in sales and sales management in a spectrum of industries and has successfully launched a variety of products to the market, including the original Rapid RH® concrete moisture tests. He currently works with Wagner Meters as our Rapid RH® product sales manager.

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