ASTM F1869 is the standard test method for measuring the moisture vapor emission rate (MVER) of a concrete subfloor using anhydrous calcium chloride. A small dish of the salt sits under a sealed plastic dome on the bare concrete. Over the test period the salt absorbs moisture vapor coming off that patch, and the weight it gains is converted into a rate.
How the test works
- Condition the space. Kit instructions written to F1869 call for the area to sit at 65–85°F and 40–60% relative humidity for at least 48 hours before testing.[2] Your edition of the standard and the product instructions govern.
- Count the tests. Three tests for up to 1,000 square feet, plus one more for each additional 1,000 square feet.[2]
- Prepare bare concrete. Each test patch, at least 20 × 20 inches, is cleaned down to bare concrete, free of old adhesive, curing compound, sealer, paint or coatings.[2]
- Weigh, open and seal. The dish is weighed, opened and placed on the patch, and the dome is sealed to the slab.
- Leave it alone. The dome stays undisturbed, out of direct sun, for 60 to 72 hours.[2]
- Reweigh and calculate. The dish is resealed and weighed again, and the gain is converted to an emission rate.
- What it reports
- Moisture vapor emission rate, in pounds of moisture per 1,000 square feet per 24 hours.[3]
- What it measures
- Vapor leaving the prepared surface during the test window, which mostly reflects the upper part of the slab.
- Not intended for
- Lightweight-aggregate concrete or gypsum toppings, or readings taken over coatings, patching or leveling compounds.[3]
- What it does not do
- Measure conditions deeper in the slab, or set a pass/fail limit on its own.
Where F1869 fits today
The calcium chloride test is a long-established method, and some product instructions and specifications still ask for it. Others name the in-situ RH method instead, and some accept either one with a separate limit for each. Because the two tests measure different things, they are not interchangeable: run the method the product instructions ask for, and compare its result only with the limit written for that method.
Safety note before preparing old surfaces
Test patches have to be bare concrete, which can mean removing old flooring residue. Some older resilient flooring, backing and black “cutback” adhesives can contain asbestos. Do not grind, sand or scrape those materials until they have been confirmed safe, and follow the protective requirements that apply.[2]
Not sure which method your project needs? Compare RH and MVER, or try the moisture test checker.