Why You Need to Measure Moisture in Your Subfloor

You’re a pro. You measure the moisture in your wood flooring before installing it. And that’s because you understand how dangerous excess moisture is to flooring jobs.

But have you been measuring the subfloor for moisture, too? Whether it’s a wood or concrete subfloor, excess moisture could lurk below the surface, where it can move up into your wood floor. That means the beautiful wood floor you just laid could be in jeopardy.

A quick way to locate moisture “hot spots” in a concrete subfloor that you’ll want to test further is to use a handheld concrete moisture meter.

Yikes.

But no fear because this problem has an easy fix: test for moisture in your subfloor. And we’ll even tell you the exact tools you need to complete the job.

Why Should You Test Subfloors for Moisture?

You should test the moisture in your subfloors if you want your project to last. Bottom line.

Any unchecked moisture could lead to many issues: wood floor cupping, crowning, buckling, cracking, and in some cases, even mold or mildew.

To prevent all those costly disasters, and save you the headache of redoing the job, you must measure the moisture in the subfloor before any final preparations.

How Do You Check the Moisture Level in a Subfloor?

Depending on the type of subfloor you’ve got, there are different techniques.

Testing Concrete Subfloors

You can start by using a concrete moisture meter to locate the hot spots in the subfloor. But this is only a preliminary step. Next, use in-situ relative humidity (RH) testing, the ASTM F2170 test that many flooring manufacturers require.

We recommend pairing Wagner Meters’ C555, a concrete moisture meter, with the Rapid RH^® L6 Testing System. Used together, they give you a good picture of the moisture in the subfloor. That way, you know when to install the flooring.

The C555 has a moisture reading range from 0–6.9%, and for best practices, you’ll want to install the Rapid RH sensors wherever it registers the highest moisture levels.

When you use the Rapid RH L6 Testing System, you’re testing to ASTM F2170, the standard for in-situ RH testing of concrete. That gives you peace of mind.

Testing Wood Subfloors

You’ll need an accurate and reliable wood moisture meter.

Luckily, we’ve got just the tool: the Orion^® 950 from Wagner Meters. The Orion 950 can measure as low as 4% moisture content (the exact range varies slightly with the species setting).

But why is that so important?

What is the normal moisture reading for wood floors?

Wood flooring typically falls in the 6–9% range before installation.

However, that depends on where you live. If, for example, you live in a more humid environment, such as a coastal area, these percentages might be higher.

But no matter where you live (at the beach, the desert, or anywhere in between), you’ll want to use an accurate and reliable moisture meter like the Orion 950.

Don’t Let Flooring Failures Cost You Time or Money

Especially because the preventative measures are easy enough.

Sure, they might be costly upfront. But it’s an investment in your success. After all, investing in high-quality moisture testing tools means you don’t have to dump more money into repair jobs.

With the whole moisture testing system from Wagner Meters (the C555, Rapid RH L6, and Orion 950), you can do the job right the first time.

To learn more about what Wagner Meters’ tools can do for you, visit wagnermeters.com or call (800) 634-9961 to speak to a representative.

Previously published in Tomorrow’s Contract Floors

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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.

Last updated on October 26th, 2026