Installations: Detailed Subfloor Issues to Address

Any time you go to do a hardwood flooring installation, you must pay special attention to the National Wood Flooring Association Installation Guidelines. These guidelines outline what should and what should not be done for each subfloor type before installing hardwood flooring. You should consult the NWFA Installation guidelines for your exact situation and plan accordingly.

All subflooring will require some form of preparation, even it only means having it swept well before installation.

Concrete

Make sure that the concrete has been installed for at least 60-90 days before moisture testing it.

Moisture test only with approved and properly working moisture testing equipment. If you don't have a moisture meter to use, tape a 2' x 2' square piece of poly plastic to the concrete in three to five places. Shine a warm lamp on the concrete for 24 hours. If the plastic is cloudy or has water drops on the plastic, it is not ready to have hardwood flooring installed over the top of it.

Ensure the concrete slab is fully level over the entire installation area. If it is not, you may need to pour or have poured additional concrete in the offending areas or consult with a structural contractor to fix any structural discrepancies before installation can begin. This may be common in older homes in which the foundation may have sunk or settled over time or in homes that have been negatively affected by earthquakes. Using a 10' leveler is common in testing to see which parts of a floor are level and which aren't.

Plan to remove any previous oil or wax based sealers that may be been placed over the concrete. These types of sealers may not allow for the flooring adhesive to work properly when you lay down the hardwood floor. Add a drop of water to the concrete. If it beads up instead of flattening out, you probably have a sealer that will need to be removed.

Try scratching the surface of the concrete with a screwdriver tip or a knife. If it comes up easily and feels like sand, produces a grain or flakes off, you'll need to follow the NWFA Installation guidelines to prepare the concrete to receive adhesive.

Wood

Look at the wood subflooring and notice any twists, bowing or denting. If these are present, you'll need to have any structural damage beneath repaired. Walk across the entirety of the floor and listen for squeaks. If the subfloor squeaks now, it will still squeak after the hardwood floor is installed. Fix the squeaks now before you install.

Don't nail down a floor directly over particle board, ever.

Other Issues

Always be prepared for surprises. Examples of surprises include: finding old drain holes that are no longer used. These will need to be filled and leveled off. Remodels involving removing previously installed sliding glass doors will require repair to make the floor level in those places. Take the time necessary to correct any and all subflooring issues you may encounter before the installation begins to prevent costly and stressful mistakes later.