How to Replace a Section of Deck Board

  • 01 of 07

    Replacing a Damaged Wooden Deck Board

    cupped deck boards
    Wooden deck boards can cup depending on how they are laid down.

    Replacing a rotted, split, or otherwise damaged deck board is almost as simple as cutting out the section of old board and replacing it with new material. The only additional step is installing support blocks alongside the joists (the horizontal structural members supporting the surface deck boards). This method works well if you don't want to remove and replace the entire board. Alternatively, you can simply remove the old board entirely and replace it with a matching length of new decking board.

    It's best to use the same type of lumber in the patch as is found in the rest of the deck. 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.

    Tools and Materials You'll Need

    • Eye protection
    • Speed square
    • Pencil
    • Jigsaw
    • Drill-driver
    • Pressure-treated 2 x 4 board, 24 inches long
    • Tape measure
    • Circular saw or miter saw (optional)
    • 1/8-inch drill bit
    • 2 1/2-inch and 3-inch deck screws
    • Deck board lumber that matches the old deck boards
    • Deck wood finish (as needed)
    Continue to 2 of 7 below.
  • 02 of 07

    Plan the Cut

    Examine the area around the damaged section of the deck board, noting the locations of the joists and the end seams on the board. The goal is to cut out the damaged section cleanly and make the repair look as natural as possible. The repair will look best if the cuts are at least one joist space away from the end joints on the same board. If you can, also plan the cuts so that the new joints do not line up side-to-side with joints in adjoining rows of decking boards. For long-term stability, the cut-out section must span at least two joist spaces.

    Identify the two joists where you will make the cuts to remove the bad section of deck board. Use the speed square to mark cutting lines on the bad deck board along the inside face of each joist. 

    Continue to 3 of 7 below.
  • 03 of 07

    Remove the Bad Section

    Put on eye protection. Cut along the marked lines on the damaged decking board, using a jigsaw. 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. The saw blade should cut right along the inside face of the joist.

    Remove the screws securing the damaged section of decking board, using a drill-driver. Remove the board section. (If the board is nailed in place, pry up the nails with a cat's paw or pry bar). 

    Continue to 4 of 7 below.
  • 04 of 07

    Cut the Support Blocks

    Cut two 12-inch-long sections of 2 x 4 lumber for the support blocks, using a circular saw, miter saw, or jigsaw. Drill two pilot holes through each block, about 2 inches from each end, using a drill and 1/8-inch twist bit. 

    Continue to 5 of 7 below.
  • 05 of 07

    Install the Support Blocks

    Position a support block against one of the inside faces of the joists, centering it under the opening where the board was removed. Pull up the block so it is tight against the undersides of the neighboring deck boards. Fasten the block to the joist with four 2 1/2-inch deck screws,  Install the other block on the opposite side of the cut-out, using the same technique. These support blocks will provide the resting place for the ends of the new decking board. 

    Continue to 6 of 7 below.
  • 06 of 07

    Cut a New Decking Board

    Deck Board Bark Side Down
    Bark Side Down Deck Board.

    Cut the new decking board to fit snugly in the cut-out area. Note the end-grain pattern of the replacement board: If the rings of the end grain are roughly parallel to the board's width, with the grain lines running side to side, position the board so the curve of the rings faces down (this is called the bark side and indicates where the bark was on the tree). If the grain is perpendicular to the board width (grain runs up and down), you can place the board either way, but if the board has a slight cup, or curve, place it with the convex side facing up. This will help prevent cupping as the board weathers.

    Continue to 7 of 7 below.
  • 07 of 07

    Install the New Decking Board

    Place the board onto the support blocks with the bark side or concave side facing down. 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 block thickness. Also drill a pair of pilot holes at any other joists that the board spans over.

    Fasten the board to each support block (and any spanned joists) with a pair of 3-inch deck screws.

    Finish the new board to protect it from weathering and to match the coloring of the existing decking.