“I have an older trilevel home. I’ve read that hardwoods aren’t a good choice for basements because of the moisture content, but what about my main level? The main level has a kitchen, dining room, living room and bathroom, all on a concrete subfloor. Can I install hardwood, or is it still risky?”

Homes built on concrete slabs are good candidates for hardwood flooring, providing the slab doesn’t have too much moisture. Too much moisture and humid conditions can cause wood to buckle, warp or crack as the wood expands and contracts with changes in the moisture level. Which means its important to understand your subfloor before making your final decision.

A professional can help you take a moisture reading of your subfloor. Another test you can use is to mark off a 12×12 section on your concrete subfloor. Tape a clear polyethylene plastic sheet over the area and secure completely with duct tape. Leave the plastic in place for about 24 hours. If the plastic is clear with no droplets of water of any signs of moisture, you can install wood over your concrete slab.

In most cases, when your home builder constructed your home, they used a vapor barrier underneath the concrete slab. This helps moisture buildup in the concrete; yet concrete naturally has some moisture in place. For further protection, a vapor barrier should also be placed between the concrete slab and your hardwood floors. Sheets of polyethylene plastic overlapped and taped into place is one method; another is painting the slab with a moisture sealant.

Hardwood flooring is typically installed in one of two ways: nailing them to the subfloor, or gluing the flooring planks into place.

For nailing, a subfloor will be installed over the concrete. Sheets of ¾ inch pressure treated plywood can be layed over the moisture barrier, or you can also lay down lengths of pressure treated 2 x 4 studs over the moisture barrier, followed by ¾ inch plywood as your base. The studs keep the wood planks further from the slab and minimize the effects the concrete will ultimately have on the final flooring.

Gluing the wood planks directly to the slab is the second installation method. A waterproof membrane over the concrete slap will act as a barrier against future moisture problems. After the sealant has dried, apply specially prepared adhesive, and work in sections to install wood planks. The adhesive dries quickly, so you have to work fast. Wood planks use a tongue and groove locking system; once the planks are in place, simply tap with a rubber mallet to seal them in.

Have additional questions about a hardwood floor over a concrete slab? Stop by or give us a call today. We’d be happy to answer all of your questions about flooring and more.