Acceptable Moisture Content in Concrete for Wood Flooring

Moisture conditions must be checked in concrete before wood flooring can be installed, otherwise structural issues will arise across the surface.

Here, we have taken a closer look at the significance of checking this before installing wooden flooring, and how this can be done for the best results.

Why is This Important For Solid & Engineered Wood Flooring?

Depending on the wood species and type of product, if there’s high moisture present, you’re going to be susceptible to excess water damage, the likes of which can lead to distinct issues.

For example, if concrete hasn’t completely dried for hardwood floors, this will start to peel away, leaving you with a warped appearance, along with unsightly discoloration.

In fact, these floors are particularly vulnerable to damage, so although this flooring material can be refinished on numerous occasions, this will only prove effective if moisture issues have been dealt with at the earliest opportunity.

On the other hand, it’s common for engineered wood flooring to adopt the ‘floating floor’ system during installation.

Here, the damage won’t be so catastrophic, as this locks into place without glue, but again, tread with caution, as recently laid concrete without suitable moisture readings, can still jeopardise its solidity.

What Moisture Levels are Acceptable for a Solid Wood Floor?

Moisture level readings are key, and for a concrete subbase, an acceptable range should be no higher than 75%.

Anything over will be far too wet, so until you hit ideal moisture levels, don’t even think about installing your wooden flooring onto the surface until the concrete dries.

When you measure moisture content, this will be recorded as relative humidity, which compares the levels currently present, and compares this to the maximum amount possible.

Absolute humidity levels aren’t used to measure moisture, as this captures readings without taking the current temperature into account, which will of course vary depending on the environment. Regardless of temperature, the moisture levels must always be the same.

Which Concrete Moisture Testing is Best?

There’s lots of ways you can measure the moisture condition in the subbase, and one test method that always hits the mark would be the process known as ‘ASTM F 2170’, which requires the use of moisture meter probes.

You simply drill a small hole into the concrete, wait a few days, and then insert the probe to record an accurate reading over current moisture levels.

Another common method would be the plastic sheet method (ASTM D 4263), in which plastic sheets are placed onto the concrete subfloor.

You then wait a few days, before taking a humidity reading from underneath the plastic using a hygrometer, but even simple common sense can do the trick, so if you can smell damp, it’s likely that moisture levels are too high.

How Do You Get Moisture Out of Concrete?

The cheapest method to gaining acceptable moisture levels would be improving air circulation within your room, that being opening up doors and windows to allow this to move around more freely.

If after the initial drying process hasn’t done the trick, you can turn to dehumidifiers, which will draw air from the room, and using cooled coils, the moisture is removed, before it’s released back into the atmosphere.

How Do You Lay Solid Wood Floors Onto a Concrete Slab?

Once you’re happy the level of moisture content within each concrete slab is suitable, you can of course get stuck into the main installation process, and as with all projects, following a proven, systematic approach will achieve the best results.

To start with, you’ll need to determine which materials are being used to fix your floor. On one hand, you could opt for glue, which must be spread consistently across the concrete subfloor before installation begins. This has always been a popular choice, owing to its flexibility.

You can also nail flooring down, which in fact, happened to be the only trusted method before the emergence of reliable adhesives.

The main consideration here would be fixing these in place, but in a way that keeps them hidden from plain sight, otherwise the finish won’t be as pleasing on the eye.

Now, check concrete slabs are flat, level and cured. The latter refers to current temperature conditions, which will be dictated not only by excess moisture readings, but also the general humidity percentages from the surrounding air.

When it comes to hardwood flooring, its best to work in small sections at one time, and definitely lay out your materials roughly at the very start, that way, you can determine if you need more, and whether certain areas require more elaborate craftsmanship to maintain a neat flooring product for all to see.

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