Planning Your Deck Project
A well-built deck adds living space and value to your home. This calculator helps you determine how many deck boards, screws, and other materials you need for your project.
Critical planning steps:
- Check local codes: Permits, setbacks, railings, and ledger board requirements
- Inspect the ledger: Must be properly attached with flashing
- Plan for drainage: Slope deck 1/8" per foot away from house
- Check utilities: Know where underground lines are before digging
- Consider access: Plan for stairs and any built-in features
Decking Material Comparison
| Material | Cost/ln ft | Lifespan | Maintenance |
|---|---|---|---|
| Pressure Treated Pine | $2-4 | 15-20 yrs | High |
| Cedar | $4-8 | 20-25 yrs | Medium |
| Redwood | $8-12 | 25-30 yrs | Medium |
| Composite | $6-15 | 25-30 yrs | Low |
| PVC/Plastic | $8-15 | 30+ yrs | Very Low |
Deck Board Spacing Guide
🪵 Wood Decking
- Dry wood: 1/8" to 1/4" gap
- Wet/green wood: Install tight (will shrink)
- Use 16d nail or spacers for consistency
- Gap allows drainage and expansion
🔧 Composite Decking
- Side gap: 1/8" to 3/16" (less expansion)
- End gap: 1/8" for every 20°F temp range
- Follow manufacturer's exact specs
- Use hidden fastener systems when possible
How to Calculate Deck Materials
1. Deck Area = Length × Width (in sq ft)
2. Board Coverage = Board Width ÷ 12 × Board Length
3. Boards Needed = (Deck Area ÷ Board Coverage) × 1.10
4. Screws = 2 per joist intersection (350-400 per 100 sq ft)
Don't forget:
- Add 10-15% extra for waste and cuts
- Joists typically spaced 16" on center
- Staggered end joints look better and are stronger
Example: 12×16 ft Deck
Scenario: Building a 12×16 ft deck using 5.5" wide × 12 ft composite boards.
- Deck area: 12 × 16 = 192 sq ft
- Board coverage: (5.5 ÷ 12) × 12 = 5.5 sq ft per board
- Boards needed: 192 ÷ 5.5 = 35 boards
- Add 10% waste: 35 × 1.10 = 39 boards
- Screws: ~700-800 deck screws (4 boxes)
Result: Buy 39-40 deck boards. Don't forget joists, concrete, posts, and hardware!