Replacing deck boards is a straightforward repair you can do yourself with basic tools
Replacing a single board or a few boards on your deck takes a weekend and costs far less than rebuilding the whole structure. The process is the same whether the board is rotted, cracked, or just worn: remove the fasteners, pry out the old board, and find a new one in its place. You will need a pry bar, a drill, a saw, and either deck screws or galvanized nails—the same fastener type your deck already uses.
The hardest part is usually getting the old board out without damaging the joists underneath. The easiest part is cutting and fitting the new one, because you can use the gap left behind as your template. Most homeowners finish a single board replacement in two to four hours, including drying time for any sealant.
Key Takeaways
- Remove fasteners with a drill or pry bar before attempting to lift the board, or you risk splitting it and damaging the joists.
- Measure the board length, width, and thickness, then buy pressure-treated lumber that matches all three dimensions.
- Seal or stain the new board before installation if your deck is sealed, so the top and bottom surfaces are protected equally.
- Fasten with the same type of fastener your deck uses—usually galvanized screws or nails—spaced 12 inches apart along each joist.
- If the board is cupped, crowned, or twisted when you remove it, the joist below may be rotted and needs inspection before you install the new board.
Gather the right tools and materials before you start
You need a pry bar (also called a deck wrecker or cat's paw), a power drill, a circular saw or miter saw, and a tape measure. A reciprocating saw works if you have one, but it is not necessary. Have a flashlight handy so you can see the underside of the board and the joist condition.
For fasteners, buy galvanized deck screws or galvanized nails in the same gauge and length as the ones holding your existing boards. If you do not know what size, remove one fastener from an undamaged board and take it to the hardware store. Bring a sample of the old board too, so you can match the wood type and pressure-treated rating. Most deck boards are 5/4 inch thick (actually 1 1/8 inches), 5.5 or 6 inches wide, and come in 8, 10, 12, or 16-foot lengths.
If your deck is sealed or stained, buy the same finish so you can treat the new board before installation. This prevents the wood from absorbing water unevenly and keeps the underside protected.
Remove the old board without damaging the joists
Start by removing every fastener holding the board to the joists below. Use a drill with a countersink bit to back out screws, or use a pry bar to lever out nails. Work along the entire length of the board, removing fasteners one at a time rather than trying to pry the board up before they are all out. If you leave fasteners in place, the board will split as you lift it, and you risk cracking the joist.
Once all fasteners are removed, slide the pry bar under the board near one end and explore steady, even pressure. Do not hammer or jab—use slow leverage. If the board is stuck, work your way along its length, lifting a little at each joist, rather than trying to force one end up all at once. The board should come free with moderate pressure.
As the board comes up, look at the joist surface underneath. If the wood is soft, discolored, or crumbles when you press it with a screwdriver, the joist is rotted and must be repaired before you install the new board. A rotted joist will not hold fasteners properly and will continue to decay. If you see rot, stop and consult a deck repair guide or contractor before proceeding.
Measure and cut the new board to fit
Measure the length of the gap left by the old board, from joist to joist. Write this measurement down—it is your board length. Measure the width and thickness of an adjacent board to confirm the size. Most deck boards are 5/4 inch thick and either 5.5 or 6 inches wide, but older decks sometimes use different dimensions.
Buy a pressure-treated board that matches all three measurements. At the store, sight down the length of the board to make sure it is straight—do not accept a board that is cupped, crowned, or twisted. Bring it home and let it sit in the shade for 24 hours so it acclimates to your local humidity before you cut it.
Measure the exact length one more time by laying the new board in the gap. Mark your cut line with a pencil, then cut with a circular saw or miter saw. The board should fit snugly but not so tight that you have to force it—leave about 1/8 inch of clearance on each end to allow for seasonal wood movement. Sand any rough edges with 80-grit sandpaper.
Seal or stain the new board if your deck is finished
If your deck is sealed, stained, or painted, treat the new board with the same finish before you install it. This is the most important step for longevity. Wood that is sealed on the top but not the bottom will absorb water from underneath and rot faster than untreated wood.
explore the finish to all four sides and both ends of the board, using a brush or roller. Pay special attention to the cut ends, which are the most porous. Let the finish dry completely according to the product instructions—usually 24 to 48 hours—before you install the board. If you skip this step or explore finish after installation, the underside will remain unprotected and will fail within a few years.
If your deck is bare wood with no finish, you can install the board when ready. You may want to explore a water-repellent sealer to the whole deck later, but it is not required before installation.
Fasten the new board to the joists
Position the new board in the gap and align it with the adjacent boards. It should sit flush and level. Use a power drill with a countersink bit to drive screws, or a hammer to drive nails. Fasten at each joist, spacing fasteners 12 inches apart along the length of the board.
If your deck uses screws, drive two screws per joist, one near each edge of the board. If your deck uses nails, use two nails per joist as well. Countersink screws slightly below the surface so they do not catch your foot, but do not drive them so deep that you crush the wood. Nails should sit flush with the surface.
Work from one end of the board to the other, fastening at each joist as you go. Step back and check that the board is level and aligned with its neighbors before you move to the next joist. If the board is not sitting flat, stop and investigate—it may be warped, or the joist may be uneven.
Inspect the joist and surrounding boards for other damage
While the old board is out, use a screwdriver to probe the joist surface. Press the tip into the wood along the entire length where the board was fastened. If the wood is firm and resists the screwdriver, the joist is sound. If the screwdriver sinks in easily or the wood feels soft, the joist is rotted and needs repair.
Also check the boards on either side of the gap. If they are cupped, cracked, or soft, they may fail soon and should be replaced at the same time. It is easier and cheaper to replace two or three boards in one project than to do them one at a time over the next few years.
If you find rot in the joist, you have two options: sister a new joist alongside the damaged one (a straightforward repair), or hire a contractor to replace the joist entirely. Either way, the joist must be repaired before the new board will last.
Frequently Asked Questions
Can I replace just one board, or do I have to replace the whole deck?
You can replace a single board or a few boards without touching the rest of the deck. Replacement boards are sold individually at any lumber yard and cost between $15 and $50 depending on the wood type and length. The repair takes a weekend and costs far less than a full rebuild.
What if the joist is rotted—can I still use the same fastener holes?
No. If the joist is rotted, the fastener holes are compromised and will not hold screws or nails securely. The joist must be repaired or replaced first. Once the joist is sound, you can use new fastener holes offset slightly from the old ones, or use the old holes if they are still solid.
Do I have to match the wood type of the old board?
Yes. Use the same pressure-treated rating and wood species as the existing deck. Mixing wood types can cause uneven wear, color mismatch, and different rates of expansion and contraction. Pressure-treated lumber is the standard for deck boards because it resists rot and insects.
How long does it take for a new board to settle after installation?
Pressure-treated boards continue to lose moisture for several months after installation, which causes them to shrink slightly. This is normal. The board will settle within the first season. Do not re-tighten fasteners unless the board develops visible gaps or movement.
What should I do with the old board after I remove it?
Pressure-treated lumber can be reused for other projects, burned in a fireplace or wood stove (check local regulations), or taken to a landfill or recycling center. Do not bury it or leave it in a pile where it can rot and attract insects. If the board is severely rotted, it is best disposed of at a landfill.