Can Wood Flooring Be Installed Over Concrete?

Yes, wood flooring can be installed over concrete, but this is one of those situations where what happens before the wood goes down can be just as important as the flooring you choose.

Concrete and wood behave very differently. Concrete can contain and transmit moisture, while wood naturally expands and contracts as moisture and humidity change. If we're going to put the two together, we need to make sure the slab and flooring system are actually ready for each other.

The National Wood Flooring Association says both solid and engineered wood can be installed over concrete when the slab is properly prepared and the particular flooring and installation system allow it. The requirements of the flooring and adhesive manufacturers ultimately determine what can be installed and how.

For most concrete-slab projects, engineered hardwood is going to give us more installation options. Engineered wood is constructed in layers, which makes it more dimensionally stable than traditional solid hardwood as conditions change. Depending on the product, it may be glued directly to properly prepared concrete or installed as a floating floor over an approved underlayment. Some manufacturers have very specific limitations, though. For example, Shaw states that its solid hardwood requires a nail-down installation while certain engineered products can be floated over a concrete subfloor.

Before we install anything, one of the biggest things we're concerned about is moisture.

You can't look at a concrete slab and tell how much moisture is in it. You also can't assume an older slab is dry simply because it's been there for 20, 30, or 50 years. The NWFA specifically recommends evaluating old slabs for moisture just like newer slabs and following the flooring and adhesive manufacturer's moisture limits.

That's important because excessive moisture coming through concrete can create serious problems for a wood floor. Depending on the system, that may mean using an approved vapor retarder, moisture-control system, or adhesive designed to provide moisture protection. The solution depends on the moisture readings and the products we're installing.

We also need to look at the condition of the concrete itself.

The slab needs to be sufficiently flat for the flooring being installed. High and low areas may need to be corrected, cracks and damaged areas need to be evaluated, and contaminants such as paint, oil, wax, sealers, or old adhesives may need to be removed. NWFA guidance calls for concrete used beneath wood flooring to be dry, flat, and free from contaminants and problematic loose or hollow areas.

This is where our experience working with concrete becomes particularly useful. Sometimes the best thing we can do for a wood floor has nothing to do with the wood itself. It's correcting the concrete underneath it before we ever open the first box of flooring.

So, can wood flooring be installed over concrete?

Absolutely.

But we wouldn't recommend simply buying hardwood and gluing it to a slab because somebody says the product can be installed over concrete. We want to know what kind of wood we're working with, what installation method the manufacturer allows, how flat the slab is, what condition it's in, and most importantly, what the moisture conditions look like.

If those things check out and the correct flooring system is selected, there's no reason a concrete slab can't be the foundation for a beautiful wood floor.