Building a deck is one of the best home improvement investments — outdoor living space that typically returns 65–75% of its cost at resale. But between decking, framing, fasteners, railing, and hardware, the materials list gets long fast. Here is how to calculate everything you need before the first board is cut.
| Nominal Size | Actual Width | Width + Gap (1/8”) | Boards per Linear Ft of Width |
|---|---|---|---|
| 5/4 × 6 | 5.5” | 5.625” (0.469 ft) | 2.13 |
| 2 × 6 | 5.5” | 5.625” (0.469 ft) | 2.13 |
| 2 × 4 | 3.5” | 3.625” (0.302 ft) | 3.31 |
| Composite (nominal 6”) | 5.5” | 5.625” to 5.75” | 2.09–2.13 |
Using 5/4×6 boards running the 16 ft direction (parallel to the 16 ft side):
If using 12 ft boards on a 16 ft run, you will need staggered butt joints (on a joist), adding about 15–20% waste for cuts and staggering:
| Component | Size | Quantity | Cost (PT lumber) |
|---|---|---|---|
| Deck boards | 5/4×6×16′ | 29 | $377–$522 ($13–$18 ea) |
| Joists | 2×8×12′ at 16” OC | 13 | $143–$195 ($11–$15 ea) |
| Beam | 2×8×16′ (doubled) | 2 | $30–$50 ($15–$25 ea) |
| Ledger board | 2×8×16′ | 1 | $15–$25 |
| Posts | 6×6×8′ PT | 3–4 | $60–$120 ($20–$30 ea) |
| Post bases | Simpson ABU66 | 3–4 | $36–$60 ($12–$15 ea) |
| Joist hangers | Simpson LUS28 | 13 | $39–$52 ($3–$4 ea) |
| Lag bolts (ledger) | 1/2” × 4” | 16 | $16–$24 ($1–$1.50 ea) |
| Deck screws | #8 × 2-1/2” | ~750 (5 lb box) | $35–$50 |
| Concrete (footings) | 60 lb bags or Sonotube | 3–4 footings | $30–$80 |
| Subtotal (no railing) | $780–$1,180 |
That works out to roughly $4–$6 per sq ft for pressure-treated framing and decking (materials only). Add railing and the total rises to $8–$15/sq ft.
| Material | Cost per Sq Ft | Lifespan | Maintenance |
|---|---|---|---|
| Pressure-treated pine | $2–$4 | 10–15 years | Stain/seal every 2–3 years |
| Cedar | $4–$7 | 15–20 years | Seal or let weather to gray |
| Redwood | $6–$12 | 20–25 years | Periodic sealing recommended |
| Composite (entry-level) | $4–$7 | 25–30 years | Annual cleaning only |
| Composite (premium) | $8–$14 | 30–50 years | Annual cleaning only |
| PVC / cellular PVC | $9–$16 | 30–50 years | Minimal |
| Ipe (hardwood) | $10–$20 | 40–75 years | Oil annually or let weather |
When comparing cost, factor in the lifetime: pressure-treated decking at $3/sq ft replaced twice in 30 years ($6/sq ft lifetime + staining costs) often costs more than composite at $8/sq ft lasting the full 30 years with no maintenance.
| Decking Type | Joist Spacing | Notes |
|---|---|---|
| 5/4×6 wood (perpendicular) | 16” OC | Standard for most residential decks |
| 5/4×6 wood (diagonal 45°) | 12” OC | Diagonal adds visual interest but uses more material |
| 2×6 wood (perpendicular) | 24” OC | Thicker board spans further |
| Most composites (perpendicular) | 16” OC | Check manufacturer specs — some require 12” |
| Most composites (diagonal) | 12” OC | Always follow manufacturer's installation guide |
For face-screwed decking (standard method):
For a 192 sq ft deck: 192 × 4.5 = ~864 screws. A 5 lb box of deck screws contains approximately 700–900 screws. Buy two boxes.
For hidden fasteners (Camo, Tiger Claw, etc.): count the number of joist-board intersections. Each intersection needs one clip. For our example: 26 board rows × 13 joists = 338 clips plus edge fasteners.
Railing is required by code for any deck over 30 inches above grade (24 inches in some jurisdictions). Estimate railing materials by total linear footage of railing:
Estimate your complete deck with our Deck Calculator, calculate concrete footings with the Concrete Calculator, and plan your lumber order with the Lumber Calculator.
Materials only: $8-$15/sq ft (pressure-treated) or $15-$30/sq ft (composite). Fully installed with labor: $20-$35/sq ft (PT) or $35-$60/sq ft (composite). A basic 300 sq ft pressure-treated deck costs $6,000-$10,500 installed, while premium composite runs $10,500-$18,000.
Most commonly perpendicular to the house (and parallel to the joists' direction of run). This is structurally efficient and creates clean sightlines from the door. Parallel to the house or diagonal patterns are purely aesthetic choices but may require closer joist spacing and produce more waste.
1 to 1.5 inches past the outer joist or fascia board. This creates a clean edge and allows water to drip off rather than running down the face of the framing. Never exceed 2 inches or the board edges will flex under foot traffic.
Almost always yes, if the deck is attached to the house or more than 30 inches above grade. Even freestanding ground-level decks may require permits depending on size and jurisdiction. Permits ensure the structure meets load requirements (40 psf live, 10 psf dead is typical) and proper ledger attachment to prevent collapse.
Wait until the wood moisture content drops below 15% — typically 2-4 weeks for kiln-dried after treatment (KDAT) lumber or 2-3 months for wet lumber. Test by sprinkling water: if it beads up, the wood is too wet. If it soaks in, you are ready to stain.