Deck Board Spacing with Chalk
Keep an eye on things and adjust the deck board spacing as needed
Set the first board along a chalk line to start straight. Then sight down the boards occasionally to make sure they’re staying straight. If they’re not, vary the size of the gap between boards gradually over a few rows as needed to straighten them. The slight changes in deck board spacing won’t be noticeable in the finished deck.
Measure an equal distance in from each end of the deck, allowing for an overhang (if desired), and snap a chalk line as a guide for the first row of decking. Align the first row with the chalk line and nail or screw the boards to the joists. Then use spacers at each joist to keep the gap between boards consistent and to keep the boards running straight. Sixteen-penny nails are about the right size for spacing between deck boards. But sight down your boards occasionally as well. You can easily spot when a board is off.
Straighten crooked boards with a chisel, clamp or nail
Chisel technique with nails used for decking spacers
Start nails into the deck board. Drive a 3/4-in. wood chisel into the joist and tight to the edge of the deck board with the bevel facing you. Pull back on the chisel until the deck board is tight to your spacer and drive the nails.
Clamp technique with nails for decking spacers
Straighten a crooked board by slipping a pipe clamp across the end and gradually tightening it as you add nails. This only works if you’re letting the ends of the boards run long and cutting them off later.
Nail technique with nails for decking spacers
Drive a toenail into the edge of the board for an extra boost. A few extra whacks will nudge the board into position.
Most deck boards are relatively straight and easy to lay, but there are always a few that need a little extra coaxing. Start on one end of bent boards and straighten them as you nail or screw them to each consecutive joist. Position the board so it bends away from installing decking. Then pull or push the bent end against the spacers as you work down the length of the board. Occasionally you’ll run into boards that are too crooked to bend easily by hand. The photos here show three of our favorite tricks for straightening these stubborn boards.
Deck board spacing: Plan ahead for the last board
Adjust spacing between deck boards
Measure to the house at both ends and in the center when you get within about 5 ft. of the wall. Adjust the spacing between deck boards gradually over the next 10 rows of decking until the distance to the house is equal.
The last board won’t look good if it’s skinny or cut at an angle. In most cases, it’s best to start with a full board on the outside edge of the deck and work toward the house so the odd board is less visible. Then measure when you’re 4 to 5 ft. away from the house and adjust the gap sizes to be sure the last board is a consistent width.
Screws or Nails for Deck: Predrill screws and blunt nailheads to prevent splitting
Drill pilot holes for screws at board ends so the wood doesn’t split later. Start the holes about 1/2 in. from the end of the board.
Blunt nail tips
Blunt the tip of a nail with your hammer to help avoid splits. The nail will punch through the wood rather than wedging it apart.
What Size Screws for Decking?
Should you use screws or nails for deck? Screws are notorious for splitting deck boards. They tend to push the wood fibers apart rather than tear through them like nails. Even boards that look good initially can get little “cat’s-eye” splits later as the wood dries. If you plan to use screws, try these solutions. Look for screws with self-drilling points. This type of screw does a pretty good job of drilling through rather than splitting the wood. Even with drill-point screws, I’d recommend predrilling the ends of boards, which are prone to splitting. If you’re willing to devote the time, you’ll find that predrilling decking for all of the screws will result in a top-notch job with zero splitting. For best results, choose a bit size that allows the screw threads to slide through the hole without catching.
Even nails can cause splitting, especially near the ends of boards. Avoid this problem by predrilling a hole the size of the nail shank. Another trick is to blunt the tip of the nail with your hammer before pounding it in. “Splitless” ring-shank nails work well but can bend and break, especially near knots.
Cut the ends all at once for a crisp, straight edge
Trim boards after nailing them
Snap the cutting line on the deck. Then measure from the edge of your saw blade to the edge of your saw’s base. Mark that distance from the line and screw down a straight board. Run the saw’s base against the straightedge to cut the deck boards perfectly straight.
Cutting the ends of deck boards as you go not only takes longer, but it’s harder to get a crisp, straight line. A better approach is to let the deck boards run wild as shown in the photo. Then screw a straight board to the deck as a saw guide and cut all the boards at once. Since you can’t saw right up to a wall or other obstruction, make sure to precut these boards to the right length first. Even if I’m using a straightedge guide, I like to snap a chalk line as an extra precaution. That way, if the guide is positioned incorrectly, you’ll notice the mistake before it’s too late. Screw down both ends of your straightedge after marking the decking. Then measure the distance from the line to the straightedge in the center to make sure it’s the same as the end measurements. If necessary, bend the guide board until the measurement is the same and screw down the center. Run your saw along the straightedge to cut off the boards.
Tip: Sight down and straighten outside joists before nailing deck boards to them.
Avoid ugly hammer marks
Start the nail. Then slip a small square of 1/4-in. plywood over the nail and swing away. Remove the plywood for the last blow.
Nails are easier to drive if you take a full swing. But the downside is that if you miss the nailhead, you’ll leave a deep “elephant track” in the decking. Use a 1/4-in. plywood cushion to protect the deck boards in case you miss with a hammer. It allows you to concentrate on nailing without worrying about denting the deck boards. Next, learn how to choose the best deck finish here.
Required Tools for this Project
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
- Chalk line
- Circular saw
- Cordless drill
- Drill bit set
- Miter saw
- Pry bar
- Safety glasses
- Tape measure
- Wood chisel
Required Materials for this Project
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.
- 16d galvanized nails
- Galvanized or stainless steel screws