How to Install Hardwood Floors Over Concrete

Installing hardwood over concrete requires a moisture barrier and subfloor system to prevent water damage and provide proper support. The process involves moisture testing, installing a vapor barrier, adding a plywood subfloor, then laying your hardwood flooring.

  1. Measure Moisture First. Wait at least 60 days after concrete pour before testing. Use a concrete moisture meter or plastic sheet test. Tape plastic sheets to several areas of the concrete and check after 24 hours for condensation. If moisture is present, apply concrete sealer and wait for complete curing before proceeding.
  2. Create a Flat Foundation. Remove all dirt, debris, and adhesive residue. Check for level using a 4-foot level - variations should not exceed 3/16 inch over 10 feet. Fill low spots with self-leveling compound and grind down high spots. Allow compound to cure completely before continuing.
  3. Block Moisture Rising. Roll out 6-mil polyethylene sheeting across the entire floor, overlapping seams by 6 inches. Seal all seams with waterproof tape. Run the barrier up walls by 2 inches and trim after flooring installation. This prevents moisture from reaching your wood floors.
  4. Lay the Subfloor Base. For sleeper system, attach 2x4 sleepers to concrete every 16 inches using concrete screws or construction adhesive. Fill between sleepers with rigid foam insulation. Alternatively, install 3/4-inch plywood subfloor directly over vapor barrier using concrete screws every 8 inches. Leave 1/4-inch gaps between plywood sheets for expansion.
  5. Let Wood Adjust. Bring flooring materials into the room 3-7 days before installation. Maintain room temperature between 60-80°F and humidity between 30-50%. Stack boards with spacers between layers to allow air circulation. This prevents warping and shrinking after installation.
  6. Add Required Underlayment. Some engineered hardwood requires specific underlayment over the subfloor. Roll out according to manufacturer directions, butting seams tightly without overlapping. Tape seams if specified. Skip this step if installing solid hardwood, which goes directly on the subfloor.
  7. Start the First Row. Start along the longest, straightest wall. Install first row with groove side toward the wall, leaving 1/2-inch expansion gap. Use flooring nailer or approved screws to secure each board. Stagger end joints by at least 6 inches between rows. Check that rows stay straight and adjust as needed.
  8. Complete and Seal. Continue installing row by row, using a pull bar for the final rows. Install transition strips at doorways and baseboards around the perimeter. Remove spacers and install quarter-round molding to cover expansion gaps. Clean the floor thoroughly and apply any required finish coats if installing unfinished hardwood.