By the RJ Commercial Flooring Team, 50 years installing institutional flooring across Northern California.
Concrete moisture testing before flooring means measuring the slab with a quantitative ASTM method, under the building's normal operating conditions, and comparing the result with the written limit of the exact flooring and adhesive being installed. The two methods in use are ASTM F2170, which reads relative humidity inside the slab with in situ probes, and ASTM F1869, which measures the moisture vapor emission rate at the surface with calcium chloride. Both are typically run at three locations for the first 1,000 square feet and one more for each additional 1,000. ASTM F710 calls for moisture testing on every slab regardless of age or grade level, plus a pH test, and it defers to the manufacturer's written instructions. A handheld meter reading is not a substitute. RJ Commercial Flooring has installed institutional flooring across Northern California for 50 years. If slab testing is on your schedule, talk to us before flooring is ordered.
A slab can look dry and still hold enough moisture to break down adhesive once it is covered. Our guide to why commercial floors fail covers what that damage looks like. This post covers running the test and reading the result.
The current edition of ASTM F710, the practice for preparing concrete floors to receive resilient flooring, says all concrete slabs should be tested for moisture regardless of age or grade level, and all concrete floors for pH. It also states that it does not supersede the flooring or adhesive manufacturer's written instructions. So every test has three jobs: use a quantitative method the manufacturer accepts, record where, when and under what conditions each reading was taken, and give a number to compare with the published limit of the products on the job.
Results are also a snapshot. F2170 results reflect the slab at the time and locations tested, and F1869 notes that emission rates depend on environmental conditions. A test taken before the HVAC is running, or months before installation, may not reflect the slab on install day.
ASTM F2170 is the standard test method for determining relative humidity in concrete floor slabs using in situ probes, and the current edition is F2170-19a. Wagner Meters, which makes F2170 probes, summarizes the procedure in its F2170 compliance guidelines. The slab and the air above it must be at service conditions, meaning the temperature and humidity of normal use, for at least 48 hours before testing. Three holes are needed for the first 1,000 square feet and at least one more for each additional 1,000. Holes are drilled to 40% of the slab thickness for a slab drying from the top only, or 20% for one drying from both sides. Each sensor then equilibrates for at least 24 hours before a reading can be documented, down from 72 hours before the 2018 revision, and sensors need NIST-traceable calibration checked within 30 days before use.
The report should list each test location, the dates and times of measurement, the RH and temperature readings, and any condition that could affect them.
ASTM F1869 measures the moisture vapor emission rate (MVER) of a bare concrete subfloor using anhydrous calcium chloride, reported in pounds of moisture over 1,000 square feet in 24 hours. The current edition is F1869-23. Check the scope first: F1869 does not apply to gypsum concrete, floors containing lightweight aggregate, or emissions through coatings, reactive penetrants, or patching and leveling compounds. For those slabs, specify F2170.
Test kit maker Gilson's F1869 kit instructions call for the space to be held at 65 to 85°F and 40 to 60% relative humidity for at least 48 hours, a cleaned 20 by 20 inch area of bare concrete per kit, three kits for areas up to 1,000 square feet plus one per additional 1,000, and 60 to 72 hours undisturbed before weighing. Some manufacturers want both methods: the Mats Inc. instructions cited below call for F1869 and F2170 results.
Use this as a checklist when writing the testing section of a flooring specification or reviewing a test report.
| Step | ASTM F2170 (in situ RH) | ASTM F1869 (calcium chloride) |
|---|---|---|
| What it measures | Relative humidity inside the slab at a set depth | Moisture vapor emission rate from the bare surface |
| Conditions before testing | Service conditions for at least 48 hours | 65 to 85°F and 40 to 60% RH for at least 48 hours |
| Number of tests | 3 for the first 1,000 sq ft, plus 1 per additional 1,000 sq ft | 3 up to 1,000 sq ft, plus 1 per additional 1,000 sq ft |
| Preparation | Drill to 40% of slab thickness (20% if drying from both sides) and seal the sensor | Clean a 20 x 20 in. area of bare concrete per kit |
| Time before a result | At least 24 hours of equilibration | 60 to 72 hours undisturbed |
| Result reported as | % relative humidity and temperature | Pounds per 1,000 sq ft per 24 hours |
| Limits on use | Valid only for the time and locations tested | Not for lightweight aggregate, gypsum concrete, or through coatings, penetrants or patching compounds |
There is no single pass mark for a slab. The acceptable reading belongs to the flooring and adhesive system, and published limits vary widely:
The same slab can pass one system and fail another. Choose the flooring and adhesive, confirm the method and limit in that manufacturer's current instructions, then test and compare. If you are still choosing between LVT, rubber, sheet vinyl or resinous floors, our commercial flooring materials comparison explains how they differ. If readings exceed the limit, the options are more drying time, an adhesive rated for the measured level, or a mitigation system the flooring manufacturer approves. Any product change after testing means checking the readings against the new limit.
F710 calls for a pH test on all concrete floors before resilient flooring goes down, and ASTM F3441 is the current standard guide for measuring pH involving resilient flooring installations. As with moisture, the acceptable pH range comes from the adhesive manufacturer.
Handheld moisture meters help find wet areas and place test holes, but they are not an acceptance test. ASTM F2659, the guide for electronic moisture meters, focuses on the upper inch of the slab and is not intended to provide quantitative results as a basis for accepting a floor. It points to F1869 or F2170 for that.
A clear testing section in the specification should state:
Bring RJ Commercial Flooring in before materials are ordered, so the test method, the product limits and the installation schedule are agreed together instead of discovered on install day.
Talk to RJ about your slabBoth ASTM F2170 and F1869 are typically run at three locations for the first 1,000 square feet and one more for each additional 1,000, so a 5,000 square foot area needs at least seven tests per method. Check the flooring manufacturer's instructions too, since some state their own frequency.
Both methods start with at least 48 hours of stable conditions in the space. F2170 probes then need at least 24 hours to equilibrate, so a documented result takes about three days, while F1869 kits stay down for 60 to 72 hours, so a result takes four and a half to five days.
No. ASTM F2659, the guide for electronic moisture meters, covers a preliminary, comparative evaluation and is not intended as a basis for accepting a floor. Meters help locate wet areas, but F2170 or F1869 provides the number that is compared with the manufacturer's limit.
There is no single number, because the limit is set by the flooring and adhesive manufacturer and ASTM F710 defers to those written instructions. Published limits range from 86% RH for one adhesive to 99% RH for another, so confirm the limit for your exact products before testing.
RJ Commercial Flooring installs for schools, healthcare, government and senior living facilities across Northern California. See our K-12 flooring solutions, government flooring work and senior living flooring.
Let RJ help you create safer, smarter, and more durable spaces for schools, hospitals, government buildings, and senior living communities.
.svg)
