How to Calculate Decking Materials: Surface Boards, Joists & Fasteners

Most standard wood and composite decking boards are designated as "5/4 × 6", which actually measures 1 inch thick by 5-1/2 inches wide (140 mm). When installed with a recommended 3/16" to 1/4" expansion gap between planks, each board covers approximately 5.75 inches (0.479 feet) of width.

To estimate total linear feet of decking: 1. Determine board orientation (running parallel to the house or perpendicular). 2. If boards run parallel to the house length, divide deck width by effective board width (0.479 ft) to find total board rows. 3. Multiply total rows by deck length to obtain total linear footage. 4. Add 10% to 15% waste for end-squaring, staggering joints over joists, and trimming overhangs.

- **Natural Wood (Pressure Treated Pine, Cedar, Redwood)**: Supports 16 inches on-center joist spacing for straight decking, or 12 inches on-center for diagonal layouts. - **Composite & PVC Decking (Capped Composite or Cellular PVC)**: Many composite manufacturers mandate 12 inches on-center framing for residential applications to eliminate bouncy plank deflection under summer sun. **Number of Joists** = (Deck Length in inches ÷ Joist Spacing in inches) + 1

Every deck board requires two fasteners at each joist intersection: - For a 16-foot board crossing joists spaced 16" OC, there are 13 joists, requiring 26 screws per board. - As a quick estimation rule of thumb, budget **3.5 screws per square foot** of deck surface for face-screwed installations, or about 2.5 clips per square foot for hidden grooved fastener systems.