Laying a solid wood floor over concrete

Both solid wood and engineered wood flooring can be installed over a concrete subfloor. While the process differs slightly for each, following the correct steps will ensure a smooth installation. Solid wood flooring is made from a single piece of timber, which means it is particularly sensitive to changes in temperature and humidity—these fluctuations can cause the wood to expand and contract.

How to Lay Solid Wood Flooring Over a Concrete Subfloor

The first decision is how you plan to fix the planks to the subfloor:

Floating
Floating a solid wood floor with underlay is not recommended, so this method should be avoided.

Glued
Gluing is often the preferred method as it is generally the simplest. This involves applying a full layer of flexible wood adhesive to both the subfloor and the boards. A glued floor provides a solid feel underfoot, similar to a nailed floor, while allowing for natural movement in the wood due to the adhesive’s flexibility.

Nailed
Before modern adhesives, nailing was the standard method for installing solid wood flooring. Nails are inserted through the tongue of each plank so they remain hidden once the next board is fitted. As the groove locks into the tongue, the fixings are concealed, creating a clean finish.

Preparing the Concrete Subfloor

Proper preparation of the subfloor is essential before installation:

• Moisture levels: If the concrete has been recently laid, excess moisture can be a problem. Ideally, aim for 35–40% air humidity and a concrete moisture content of 2–3%.
• Drying time: Concrete typically requires about one month per inch of thickness to dry fully, and reaching ideal moisture levels can be challenging.
• Damp proofing: If moisture levels are too high, applying a surface damp-proof membrane can help resolve the issue.
• Surface condition: Ensure the subfloor is clean, free from debris, and completely level to avoid future problems with the flooring.

Never install a new floor over a subfloor with unresolved issues, as this can lead to long-term damage and poor performance.