How much material do I need for a deck?
Estimate joists and decking boards for your deck based on dimensions, joist spacing, and board width.
Deck calculator
Choosing the Right Decking Material
Deck material affects longevity, maintenance, appearance, and cost. Consider your climate, how much maintenance you are willing to do, and the look you want to achieve.
Pressure-Treated Wood: The most affordable decking material. Pine or fir infused with preservatives to resist rot and insects. Requires annual sealing or staining but can last 15–25 years with proper maintenance. Warms and cracks over time.
Cedar / Redwood: Naturally rot-resistant with beautiful grain and color. Cedar and redwood do not require chemical treatment and take stain well. More expensive than pressure-treated but lighter and less prone to warping. Fades to silver-gray if left unsealed.
Composite Decking: A blend of wood fibers and recycled plastic. Composite never needs staining or sealing, resists moisture and insects, and comes in a range of colors. Higher upfront cost but very low maintenance. Can get hot in direct sun.
PVC Decking: 100% synthetic, hollow or cellular PVC. Completely waterproof, never rots, and stays cool underfoot. PVC is the most expensive option but requires zero maintenance beyond occasional cleaning. Best for wet areas, pools, and coastal environments.
Decking Material Cheat Sheet
Use this reference to choose the right deck material:
| Material | Maintenance | Lifespan | Cost |
|---|---|---|---|
| Pressure-Treated | High (annual sealing) | 15–25 years | $ |
| Cedar / Redwood | Moderate (stain every 2–3 years) | 20–30 years | $$ |
| Composite | Low (occasional wash) | 25–30 years | $$$ |
| PVC | Minimal (rinse with hose) | 30+ years | $$$$ |
Deck building considerations
- Footings: Concrete piers below frost line, typically 4x8 feet apart
- Beams: Support the joists, sized based on span and load
- Joists: 2x6 at 16-inch spacing for most residential decks
- Decking: 5/4x6 or 2x6 boards, leave 1/8 inch gap for drainage
- Railings: Required for decks over 30 inches high
- Hardware: Use galvanized or stainless steel fasteners for outdoor use
The calculator estimates primary framing materials. Add 10-15% for waste, cuts, and additional blocking.
Worked example
For example, for a 12×10 ft deck, joists at 16-in spacing with 5.5-in wide deck boards:
- Deck area = 12 × 10 = 120 sq ft
- Joists: (10 × 12 ÷ 16) + 1 = 8.5 → 9 joists at 12 ft = 108 ft
- Deck boards: (12 × 12 ÷ 5.5) = 26.2 → 27 boards at 10 ft = 270 ft
- Add 10% for waste: 300 ft of decking, 120 ft of joists
- Also plan for hardware: joist hangers, screws, and flashing
Common mistakes
| Mistake | Why it matters |
|---|---|
| Not using proper flashing | Tape the top of each joist before decking to prevent rot and extend deck life |
| Spacing boards incorrectly | Use a 16d nail as a spacer between deck boards for proper drainage |
| Setting posts in concrete without drainage | Concrete above grade traps water against posts — slope the concrete away |