How to Replace Bad Wood Under Carpet

Lift the carpet from the floor. Start at a corner of the room, remove the quarter round of the baseboard and loosen the carpet from the nailstrips. Roll back the carpet and the padding until you expose the damaged area.

Check the area under the floor; whether it is a crawlspace or a basement to make sure the floor joists are supporting the floorboards. Increase the support if necessary by using floor jacks to lift the floor joists so they are level.

Mark off the area where the boards are damaged using a pencil and a straightedge. Keep the distance of the area to cut out at least as long as the distance from one joist to another so the repair has support. Chisel out the edge of one board if the damage is limited to just one or two boards. Split the board in half and use a pry bar to lift out the bad wood. Pull out any protruding nails. Use a circular saw to cut through just the ends of the floorboards, not the floor joists below, if the damage is more than three or four boards. Lift out the boards with a pry bar.

Take one section of the damaged wood to your hardwood flooring supply store and try to find replacement wood that matches your boards.

Measure the gap left after pulling out the bad wood. Measure the new boards to fit the space, cutting them with a wood saw. Slide the boards into the space fitting the tongue and groove joints together with a little wood glue and nails. Nail plank boards into the floor joists also using wood glue under the planks to help reduce movement. Cut the bottom edge of the groove off the last board -- if you are using tongue and groove boards -- using a chisel and hammer and tap the board in place.

Finish the wood boards to match the existing floor, if wanted. Otherwise, roll back the carpet padding and the carpet. Attach the carpet to the nail strips and reattach the quarter round of the baseboard.