Timing and planning
When should moisture testing happen?
Close enough to installation that the results still describe the slab, and only after the building has been at service conditions for the period the method requires. Testing too early on a new slab often just tells you to wait.
How long does it take?
Plan in days, not hours. Conditioning comes first (48 hours at service conditions for in-situ RH), then a 24-hour equilibration for RH probes, or 60 to 72 hours under the dome for calcium chloride. Allow for two site visits.
Who should order the test?
Usually whoever is responsible for slab readiness under the contract: often the GC on new work, or the owner or flooring contractor on a remodel. What matters is that the report goes to everyone making the installation decision.
Methods and results
Which test does my floor need?
The one named in the installation instructions for your flooring, adhesive and prep products, or in the project specification. If they name more than one, they will also give a separate limit for each.
Is there a safe number?
No single number covers every floor. Each product publishes its own limit for a specific method, and the most restrictive product in the assembly decides.
Is a handheld moisture meter good enough?
Surface meters can help survey a slab and find areas worth testing, but they are not the ASTM methods most instructions name. Use the method the documents call for.
Can I run a calcium chloride kit myself?
Kits are sold, but the result is only useful if the method is followed exactly, including conditioning, surface prep, timing and recording. If the result needs to satisfy a warranty or spec, check who is allowed to perform the test.
Floors and slabs
My new floor is waterproof. Do I still need to think about slab moisture?
Often, yes. SPC planks are 100% waterproof, but the plank being waterproof does not make the installed floor a moisture barrier: water at the edges or through the subfloor, slab moisture and leaks still need attention. Many floating-floor instructions list slab moisture requirements and underlayment rules.
My slab is 20 years old. Is it dry by now?
Possibly, but age alone does not prove it. Moisture can keep moving up from the ground, and irrigation, plumbing or a missing vapor retarder can keep a slab wetter than expected.
What about tile?
Tile set in thinset is generally more tolerant than glue-down wood or vinyl, but membranes, setting materials and underlayments can carry their own requirements. Read them.
What is the white powder on my slab?
White, powdery or crusty deposits are often salts left behind as moisture moves through concrete and evaporates. They are a reason to take moisture seriously, not a measurement.
About Vegas Flooring Outlet’s testing
Does VFO test slabs?
Vegas Flooring Outlet offers project-related concrete moisture testing before flooring, adhesive or coating installation. It reviews the project, selected products, requested method and schedule before confirming the scope.
Will VFO investigate a floor that has already failed?
No. VFO’s testing is for planning before installation. It is not a service for diagnosing installed floors or disputes.
Where does VFO work?
VFO is based at 4039 Spring Mountain Rd in Las Vegas and handles residential and commercial flooring across Nevada. Testing availability, travel and scheduling are confirmed for each project.
Still unsure? Try the moisture test checker or send VFO a testing inquiry.
Timing figures: F2170 summary, F1869 kit instructions.