One split floorboard can mar the beauty of your whole floor. While it may seem impossible to fix, it really isn't. Wood floorboards are attached to each other with interlocking tongues and grooves. They're nailed onto the floor at the tongue, which hides the nail heads. There's a surprisingly simple method for pulling a single split floorboard off the floor and replacing it with a new one.
Measure the thickness of the floorboards you're replacing. If you don't have any extras from when the floor was installed, purchase replacement boards at a floor covering store or home center.
Drill 1-inch holes at each end of the damaged board. Use masking tape to mark the maximum depth that you should drill, using the measurement you took in Step 1.
Draw two straight lines between the two holes with a pencil and a straightedge. Align the straightedge on the left and right edges of the holes when you mark the lines.
Set the depth on a circular saw to the thickness of the board. Cover the bottom of the saw with painter's tape to avoid marring the adjacent floorboards. Cut along the lines you marked in Step 3.
Remove the center portion of the board with a small pry bar.
Chisel the remaining sections of the floorboard off the floor and the adjacent boards, taking care not to damage the adjacent boards. In areas nailed in place, chisel around the nails, breaking up the wood as you go. When the nails are finally exposed, pull them out with a claw hammer or a pair of pliers.
Clean up the edges of the adjacent boards, as well as the now exposed subfloor. You'll likely need a vacuum cleaner, small broom and dustpan.
Measure the hole and cut the replacement board to fit using a circular saw or table saw.
Cut off the grooved edge on the bottom of the replacement board, which will allow it to fit over the tongue of the adjacent board.
Test fit the replacement board. If it's lower than the adjacent board, shim it higher with folded pieces of paper.
Spread carpenter's glue on the tongues and grooves of the replacement board and the existing floorboards. A thin line of glue will be enough. If you use too much, it will seep through the cracks.
Set the replacement floorboard in in place and tap it in with a rubber mallet.
Cover the replacement board with wax paper and set heavy objects such as sandbags, books or other weights on top of it.
Stain the replacement board to match the adjacent boards. Mask off the adjacent boards with painter's tape before applying the stain. Once the stain is dry, apply polyurethane to the replacement board.