Solutions for Hardwood Floors That Are Warped and Cupped

Concave Cupping

• Hardwood floor boards cup when the wood gains or loses moisture faster on one side than on the other. The surface of the floor will appear to be concave, with board edges extending higher than the center of the boards. This cupping occurs because the underside of the board is absorbing water vapor, causing wood fibers to swell. If a non-breathable surface treatment is applied to the floorboards, the cupping process will accelerate as water evaporation on the top side of the wood is effectively eliminated.

Convex Cupping

• A floor undergoes crowning or convex cupping if concave cupped boards are sanded and the high edges are cut off. If the boards later dry, the edges become lower than the surface of the board, causing gaps and convex cupping. Cupping may become permanent if the moisture source is not discovered and eliminated and the floor dried quickly enough. At this point, wood fibers may no longer be altered through the drying process.

Moisture Elimination

• The source of moisture must be determined and rectified before any repair or replacement is begun. Air circulation and dehumidifying equipment should be installed and the moisture level of the flooring monitored every two weeks to see if drying is occurring. Expect several weeks to pass before moisture readings between the face and back of the boards remain consistently balanced and unchanged for at least 30 days. If the drying process is unsuccessful, the floor may need to be completely resanded, cracks filled and a breathable finish or wax coating applied.

Board Replacement

• Allow replacement boards to acclimate by storing them in the room where they will be installed for a period of at least two weeks. Remove damaged boards using a circular saw set to the depth of the hardwood flooring. Pass the blade 1/2 inch from each side of the board, and angle cut between the first two cuts. Use a chisel to remove the old boards, and scrape away any adhesive residue. Cut a replacement board to fit, matching grain direction as exactly as possible. Apply adhesive, and fit the new board in place. Feather sand and finish as required.