How to Repair a Rotted Deck Board

D deck rot is a reality for every wooden patio exposed to the elements, but it doesn't mean you need to rebuild the entire structure. When moisture infiltrates the wood fibers and breaks them down, the board loses its structural integrity, creating a tripping hazard and an eyesore that will only spread if left unaddressed. A well-executed repair restores both safety and aesthetics by replacing the decayed timber with fresh, treated material that blends seamlessly into your existing layout. Successfully managing this repair requires precision in your cuts and a commitment to protecting the new wood. By isolating the rot and anchoring the new board firmly into the framing joists, you prevent further moisture entrapment. Once you have the hang of it, this project is a straightforward afternoon task that significantly extends the lifespan of your outdoor space.

Spot the Soft Wood. Inspect the deck for soft spots or visible fungus. Mark the boards at least six inches beyond the visibly rotted area to ensure you reach solid, healthy wood.
Nail the Exact Dimensions. Measure the distance between the center of the two joists where the new board will sit. You must cut your new board so the ends land directly in the center of a joist for proper support.
Extract the Rot. Set your circular saw depth to the exact thickness of your deck boards. Carefully cut along your marked lines and pry out the rotted section using a cat's paw or pry bar.
Shield the Frame. Once the board is removed, brush a generous layer of liquid wood preservative onto the top of the exposed joists. This prevents the remaining structure from decaying where the new board will sit.
Set the New Board. Place your new, pressure-treated board into the gap. Use spacers to maintain the consistent 1/8-inch gap between boards for proper drainage.
Lock It Down Tight. Drive two deck-rated screws into each end of the new board where it meets the joists. Ensure the heads are slightly countersunk so they sit flush with the surface.