Replacing a Section of Wooden Decking Board
Replacing a rotted, split, or otherwise damaged deck board is sometimes done by removing and replacing the entire board, but this isn't always possible or practical. When necesssary, 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.
This repair involves cutting away the damaged section of a decking board, making the cuts flush with the inside edges of the joists on either end of the removed section. Then, you will attach 2 x 4 blocking to the sides of the joists, creating cleats to support the replacement piece of decking. Finally, you'll install a new section of decking board and attach it to the joists with deck screws.
It's best to 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.
Tools and Supplies You'll Need
Plan the Cut
Examine the damaged section of the deck board and select locations to make the cuts. The goal is to cut out the damaged section cleanly and make the repair look as natural as possible. 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, and draw cutting lines across the board, flush with the inside edges of the joists. A speed square can help you mark square and straight cutting lines.
Remove the Damaged Section of Decking
Wearing eye protection, use a jigsaw and coarse wood-cutting blade to cut along the marked lines, severing 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 securing the damaged section of the 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.)
Cut and Install Support Cleats
Cut two 12-inch-long sections of 2 x 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. These cleats will provide support for the replacement piece of decking.
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.
Install the New Decking Board
Position the replacement board so the gap between the adjacent boards is uniform, then 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.
Finish the new board to protect it from weathering and to match the coloring of the existing decking.