How to Replace a Section of Decking Board

Wooden decking construction.
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Overview
  • Total Time: 4 hrs
  • Yield: 1 replaced deck board
  • Skill Level: Intermediate
Cupped deck boards
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Replacing a rotted, split, or otherwise damaged deck board is a safety precaution, as well as an aesthetic fix. If the board is not damaged but has a purely a cosmetic issue, such as a stain, you might just need to remove, flip, and refasten the unsightly piece of board. If there is damage, you can remove and replace the entire board, although this isn't always possible or practical. When necessary, you can also replace just the damaged section of the board, a process that is as simple as cutting out the section of the old board and replacing it with new material, though the preparation of joists and the new board is key.

What You'll Need

Equipment / Tools

  • Eye protection
  • Speed square
  • Carpenter's pencil
  • Screwdriver (optional)
  • Pry bar
  • Circular saw
  • Miter saw (optional)
  • Jigsaw
  • Drill driver
  • 1/8-inch drill twist bit
  • Tape measure
  • Brush for wood sealer application
  • Paintbrush for wood finish

Materials

  • Deck wood sealer (clear)
  • 16d galvanized nails
  • 2 1/2-inch galvanized deck screws
  • 1 24-inch piece pressure-treated 2-by-4 lumber
  • 3 1/2-inch galvanized deck screws
  • Deck board lumber to match existing decking boards
  • Deck wood finish (as needed)
  • 3-inch galvanized deck screws

Instructions

  1. Plan the Cut

    The goal is to cut out the damaged section cleanly and make the repair look as natural as possible.

    Examine the damaged section of the deck board and select locations to make the cuts. Ideally, the replacement board will be sized so the end joints do not align with the joints in adjoining rows of decking. It's better to stagger the joints in decking boards from row to row to create a natural look.

    Even if the damaged area is quite small, it's best for the new replacement section to span at least two joist spaces, so that it is supported in at least three locations—at the ends and at least one interim joist. Identify the two joists on either side of the damaged area. Using a speed square to mark square and straight cutting lines, draw cutting lines across the board, flush with the inside edges of the joists. 

  2. Remove the Damaged Board

    Before cutting, put on eye protection. Use a jigsaw and coarse wood-cutting blade to cut along the marked lines. Sever the damaged board exactly flush with the edges of the joists. (You can use the speed square to guide the saw if you're comfortable with this technique, otherwise simply follow the line carefully for a straight cut.) 

    Remove the screws and nails securing the damaged section of the decking board using a drill-driver, screwdriver, or a pry bar. Remove the board section.

  3. Seal Joist Rot

    Inspect and remove any rot on the joists below the damaged board you just removed. Treat and protect exposed portions of joists where rot was removed using two coats of clear sealer.

  4. Add Joist Reinforcement

    Add a reinforcing joist from pressure-treated lumber treated with clear sealer. Position the new joist tightly against the damaged joist. Attach the new joist with 16d nails or 3 1/2-inch deck screws driven every two feet.

  5. Install Support Cleats

    Cleats provide support for the replacement piece of decking

    Cut two 12-inch-long sections of a piece of 2-by-4 lumber for the support cleats, using a circular saw, miter saw, or jigsaw. Drill two pilot holes at each end of both cleats, about 2 inches from the ends, using a drill and 1/8-inch twist bit. 

    Position a support cleat against the inside face of one of the exposed joists, centering it under the opening where the board was removed. The top of the cleat should be flush with the top of the joist.

    Fasten the cleat to the joist with four 2 1/2-inch deck screws driven through the pilot holes. Repeat with the second cleat and the other joist.

  6. Cut a New Decking Board

    Cut the new piece of decking board to fit snugly in the cut-out area. 

    If the new board is already cupped in any way, position it so the crowned (convex) side faces up. This alignment will help prevent cupping as the board weathers.

    If the board has no obvious cupping, examine the end grain of the board; if there is an obvious curve to the grain pattern, position the board so the curve faces up, as in the illustration below.

    Deck Board Bark Side Down
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  7. Finish the Board

    Stain or finish the new board before installing it into place.

    Use the same type of lumber in the patch as is found in the rest of the decking. Unless you are painting the entire deck, using a different lumber species will cause the patch area to stand out from the rest of the deck.

    Weathering the Board

    If your deck has a weathered gray tone, match the new piece by treating it with a weathering solution.

    • Combine 1 cup of baking soda with 1 gallon of warm water.
    • Apply the solution with a scrub brush.
    • Rinse off.
    • Dry before installing the board.
  8. Install the New Board

    Position the finished replacement board so the gap between the adjacent boards is uniform.

    Drill two pilot holes through the board at each end, about 3/4 inch from the end, so the holes are centered over the support cleats. Also drill a pair of pilot holes at any other joists that the replacement board spans. Fasten the board to each cleat (and any spanned joists) with a pair of 3-inch deck screws driven through the pilot holes.