When building a deck, one of the most important considerations is how to properly secure the deck boards. Deck boards are usually made of wood or composite materials and laid horizontally across the deck frame. Using the right number of screws is crucial to ensure the boards stay in place and create a safe, durable surface.
Quick answers
The quick answers to how many screws deck boards need are:
- Wood deck boards typically need 2-3 screws per joist
- Composite deck boards need 1-2 screws per joist
- Screws should be installed every 12-16 inches along each joist
- Staggering screws creates a more secure connection
- Using too few screws can lead to loose, squeaky boards
- Using too many screws risks splitting the boards
The specific amount can vary based on factors like board type, size, joist spacing, and local building codes. But in general, a good rule of thumb is to use 2-3 screws to attach each wood board and 1-2 screws for composites. The screws should be staggered at 12-16 inches apart and driven into the joists below to properly secure the decking.
Choosing the right screw type
Deck screws are specially designed for securing deck boards to the framing underneath. The most common types are:
- Wood decking screws – Have coarse threads that grip wood well. Often coated to resist corrosion. Ideal for softwood and hardwood boards.
- Composite deck screws – Made for composite boards. Usually have fine threads and a smooth shank to pre-drill through materials without cracking or snapping them.
- Stainless steel – Most corrosion resistant option but also the most expensive. Provides the strongest and longest-lasting fastening.
- Coated deck screws – Have a coating such as zinc or ceramic to protect against corrosion. Less expensive than stainless steel but not as strong.
Make sure to use the screw size recommended by the deck board manufacturer. Using a screw that is too large can split the wood or cause the composite to crack.
How many screws for wood deck boards
For wood decking like cedar, redwood, or pressure-treated pine, the general recommendation is to use 2-3 screws per board at each joist:
- Use 2 screws if the boards are under 6 inches wide
- Use 3 screws for boards 6 inches or wider
The screws should be spaced apart every 12-16 inches along the length of each joist. Staggering the screws diagonally provides better holding power compared to lining them up straight.
Here are some examples of how many screws to use on wood deck boards:
| Board width | Joist spacing | Number of screws |
|---|---|---|
| 4 inches | 16 inches | 2 per joist |
| 6 inches | 12 inches | 3 per joist |
Some other best practices when screwing down wood deck boards include:
- Drill pilot holes to prevent splitting, especially near board ends
- Make sure screws are long enough to penetrate joists by at least 1 inch
- Drive screws flush with board surface, not countersunk
- Use impact driver for easiest fastening into wood
How many screws for composite decking
Composite decking is secured differently than natural wood. Composites typically require fewer screws:
- Use 1 screw per joist for boards up to 6 inches wide
- Use 2 screws for boards wider than 6 inches
The reason composites need fewer screws is their expanded size and rigid construction. Composites expand and contract less than natural wood. Too many screws can cause bumps, cracks, or compression damage.
Follow these general guidelines when installing composite deck boards:
- Space screws every 16 inches along joists
- Stagger screws diagonally for best results
- Use composite decking screws, never wood screws
- Drill pilot holes to prevent cracking and snapping
- Ensure screws are flush, not counterunk into surface
Here are some examples of proper composite deck board fastening:
| Board width | Joist spacing | Number of screws |
|---|---|---|
| 5 inches | 12 inches | 1 per joist |
| 7 inches | 16 inches | 2 per joist |
Screw placement tips
Properly locating deck screws takes some technique. Follow these tips when driving screws:
- Stagger diagonally – Alternate screws between sides of boards and joists. Creates better resistance to movement and loosening.
- Use deck board ends – Drive screws into ends of boards where possible. Provides greater holding strength.
- Allow spacing – Leave 1/8 inch gap between board ends for drainage and expansion.
- Avoid knots – Fasten screws at least 1 inch away from any knots in wood boards.
- Drive flush – Set screws flush with wood surface. Over-tightening can damage composite boards.
Proper screw placement requires attention to detail but prevents issues down the road. Taking the time to stagger screws, use board ends, and allow for spacing will lead to a long-lasting deck.
How to calculate total number of screws
Figuring out the total number of screws needed for a deck project takes a few simple calculations:
- Find the total square footage of your deck using length x width.
- Divide by the width of your deck boards to get the number of boards.
- Multiply by the number of screws per board you plan to use.
- Finally, add 10-20% extra for waste and mistakes.
For example:
- Deck size: 16 ft x 20 ft = 320 sq ft
- Using 5.5 inch wide boards means approximately 58 boards (320 / 5.5)
- With 2 screws per joist at 16 inch spacing = approximately 14 screws per board
- 58 boards x 14 screws per board = 812 screws
- Adding 15% extra brings the total to around 930 screws
Always round up and buy extra screws when estimating your deck project. Running short means extra trips to the hardware store and potential delays.
Installation tips
Here are some important installation tips when fastening down deck screws:
- Use impact driver – Far easier and faster than a regular drill/driver. Helps prevent screw stripping.
- Adjust torque setting – Set proper clutch strength so screws are driven flush, not over-tightened.
- Apply weight – Stand on boards as you screw them down to remove any bowing or warping.
- Drill pilot holes – Prevent wood splitting and composite mushrooming.
- Work outwards – Start fastening boards in center of structure and work out.
Properly driving deck screws takes some practice. Go slowly, check frequently, and make adjustments as needed. Rushing through screwing down deck boards often leads to problems down the road. Taking your time ensures boards are properly secured.
How tight should deck screws be?
Deck screws should be driven flush with board surface, not countersunk. The flush method creates a flat walking surface and prevents water pooling.
For wood decks, tighten screws just until flush. Overtightening can damage wood fibers near the surface.
With composites, take extra care not to overdrive screws. Most manufacturers recommend adjusting torque so screw heads sit perfectly flush without compressing material. Countersinking screws leads to mushrooming or cracking around the holes over time.
Ensure your drill/driver has an adjustable clutch for managing torque settings. Test on scrap material first to dial in the proper clutch strength before moving onto full deck installation.
Err on the side of slightly loose versus too tight when driving screws. You can always add another rotation if needed. Overtightened screws are impossible to undo once damaged.
Conclusion
When it comes to deck construction, properly fastening the deck boards is one of the most critical steps. Using the right number of screws prevents loose boards, prevents future repairs, and ensures people can enjoy their deck safely.
While the screw amount varies slightly between wood and composite decks, the general rule of thumb is 2-3 screws per wood board and 1-2 screws for composites. Spacing screws every 12-16 inches and staggering them diagonally provides optimal strength. Always check manufacturer guidelines and local building codes for specific requirements. Investing a little extra time fastening deck boards helps build a structurally sound, long-lasting outdoor living space.
