When it comes to building a wood deck that lasts, proper deck board spacing is one of the most important—and most overlooked—steps in the process. Whether you're a DIYer or working with a contractor, understanding how to space deck boards can help prevent costly issues like warping, cupping, or water damage down the road.
In this guide, we’ll break down how to space your deck boards and why.
Why does deck board spacing matter?
Wood is a natural material, which means it reacts to the environment. As temperatures and humidity levels change, wood expands and contracts. Without proper spacing between your deck boards, boards can push against each other, leading to buckling and cupping.
Here’s what proper spacing helps with:
- Allows for natural expansion and contraction
- Improves airflow to help boards dry faster
- Prevents water pooling, reducing potential for rot and mold
- Makes cleaning easier by allowing debris to fall through
How much space should be between deck boards?
The right gap depends on whether your lumber is wet (freshly treated) or dry (seasoned).
If your deck boards are dry:
Leave a 3/16-inch gap between each board.
Pro Tip: This is about the thickness of a 16D nail—a handy, inexpensive spacer you can use during installation. You can use 16D nails between boards to create consistent spacing as you install your deck boards.
If your deck boards are wet:
Install them without a gap. As wet boards dry out over time, they will naturally shrink, creating the ideal spacing on their own.
Test if your boards are wet or dry with the Sprinkle Test
You can sprinkle some water on your boards, if the water absorbs into the boards within 10 minutes your boards are dry. Check out our How to Stain or Seal Your Deck blog for more details on how to perform the Sprinkle Test.
Note: ProWood always recommends allowing your lumber to dry before installation, but we understand that’s not always possible for every project.
Tips for installing your deck boards
- Start from the outside edge of your deck and work your way toward the house. Why? If you need to rip (trim) the last board to fit, it’s less noticeable against the wall of your home.
- Use consistent spacers like nails or purpose-made deck board spacers.
- Check for crown orientation. Install boards crown-up (with the slight curve facing up) to help shed water.
- Fasten properly. Make sure your fasteners are rated for pressure-treated lumber per the manufacturer’s information
Are you a visual learner?
Check out our How to Space Deck Boards video where we walk through everything you need to know about deck board spacing.
Build your deck with ProWood
Choosing ProWood pressure-treated lumber ensures your deck starts with a solid foundation. When paired with proper spacing and installation techniques, you get a deck that looks great, lasts longer, and performs better through every season.
Looking for materials? Find a ProWood dealer near you.