What a Deck Costs to Build
A pressure-treated deck costs $25 to $45 per square foot installed and a composite one $40 to $80 — so a 12 × 16 ft deck is roughly $4,800 to $8,600 in treated lumber and $7,700 to $15,400 in composite. The decking itself is a minority of that: framing lumber runs $3 to $8 a linear foot and the labour of setting footings and joists is most of the difference between the two totals.
Decking material is the single biggest lever on a deck budget — the same 16 × 12 frame carries pressure-treated boards for a few hundred dollars or capped composite for several thousand. Everything under the boards costs roughly the same either way.
Count rows, not square feet
Decking is bought by the board, and the number of boards comes from the rows across the width, not from the area. A 12 ft width at 5.5 in boards with a 3/16 in gap is 26 rows — and 26 rows of 16 ft board is 416 linear feet regardless of how you slice the area.
Buying boards the exact length of the deck removes every butt joint. A butt joint needs doubled blocking underneath and becomes the place water sits, so a 16 ft deck built from 12 ft boards costs more in framing and lasts less time.
Framing is the same whatever you walk on
Joists at 16 in on centre, a rim, posts, footings and hardware come out roughly the same for a pressure-treated deck and a composite one. Composite often requires 12 in spacing for diagonal layouts, which adds joists — check the board manufacturer before the framing goes down, not after.
Hidden fasteners cost several times what deck screws do and take longer to install, but they are the reason a composite deck has no visible screw heads. That is a finish decision with a real price.
Where the codes bite
Ledger attachment and footing depth are the two things inspectors fail decks for. The ledger has to be through-bolted with flashing above it; a deck that pulls off a house almost always pulled the ledger. Footings go below the frost line, which in a cold climate is deeper than the post length people plan for.
The American Wood Council publishes a prescriptive deck guide (DCA 6) that most jurisdictions accept directly. Building to it is cheaper than redesigning after a failed inspection.
Typical costs, US, 2026
| Item | Typical range |
|---|---|
| Pressure-treated decking | $2–$5 per linear ft |
| Capped composite decking | $4–$12 per linear ft |
| Framing lumber, joists and beams | $3–$8 per linear ft |
| Deck, materials and labour, pressure-treated | $25–$45 per sq ft |
| Deck, materials and labour, composite | $40–$80 per sq ft |
Excludes railings, stairs, permits, and any footing work beyond standard piers. Railings alone commonly add 15–25% to a deck of this size.
Ranges as of 2026 and indicative rather than sourced from a price index. Use them to sanity-check a quote, not to replace one — regional labour rates move these figures more than any material choice.
Questions people actually ask
- Is composite worth the price difference?
- Over 20 years, usually — composite needs washing rather than staining, and a stain cycle every two or three years on a pressure-treated deck adds up in both money and weekends. Over five years, no.
- How much does the gap between boards matter?
- Enough to determine whether the deck cups. Wet-treated lumber arrives swollen and shrinks, so it gets a tight 1/8 in gap; kiln-dried and composite boards do not shrink and need the full 3/16 in built in.
- What does a permit cost?
- Varies by jurisdiction, commonly a few hundred dollars. Building without one is cheap right up to the point of selling the house.
Sources: American Wood Council DCA 6 — prescriptive residential deck construction, International Residential Code R507 — decks