— Here is the honest number: deck building cost per square foot runs $20–$45 installed in 2026, and the spread is not hedging. Pressure-treated wood installs at $12–$22/sq ft, composite at $20–$35, and PVC at $25–$40, so on a 400 sq ft deck the material choice alone moves the total from $5,000 to $17,000. Quotes vary even for the same material because framing and labor make up more than half the price, and many bids bury footings, railing, and stairs in a lump sum. Below, we break the deck cost down line by line, the way we quote it.
Deck Building Cost per Square Foot at a Glance
The table below summarizes installed pricing for a 400 sq ft deck — materials and labor, no site surprises. Lumber prices are stable after the 2021–22 spike, when framing lumber briefly doubled, so wood is back to being the value play.
| Material | Installed $/sq ft | 400 sq ft total | Lifespan |
|---|---|---|---|
| Pressure-treated wood | $12–$22 | $5,000–$8,000 | 15–25 years with upkeep |
| Composite (Trex, TimberTech, Fiberon) | $20–$35 | $9,000–$15,000 | 25–30 years |
| PVC | $25–$40 | $11,000–$17,000 | 25–30+ years |
The choice changes everything downstream, from repair to resale — our composite vs. wood comparison walks through the trade-offs.
Cost per Square Foot, Line by Line
The deck building cost per square foot on paper is five line items. We quote it this way so you can compare bids without decoding them.
| Line item | Cost | What it covers |
|---|---|---|
| Footings (set) | $1,500–$3,000 per deck | 8–12 concrete piers, excavation, post anchors |
| Framing — joists, beams, ledger | $4–$7 per sq ft | $1,600–$2,800 on a 400 sq ft deck |
| Decking boards | $5–$15 per sq ft | PT $5–6; cedar $7–9; composite $8–12; PVC $10–15 |
| Labor | $10–$18 per sq ft | Deck labor cost per square foot, crew and tools |
| Railing | $25–$100 per linear ft | Handrail and balusters, installed |
| Stairs | $50–$150 per step | Materials plus labor; typical deck needs 3–5 steps |
Footings are quoted as a set, not per square foot, and they are the first line contractors round up — a $2,000 footing line on a 400 sq ft deck is normal. Railing is the most padded line; we priced it material by material in our deck railing cost breakdown. Stairs are per step because step count is fixed by deck height, not footprint. In most bids, the deck material cost — the boards alone — is a third of the total or less. Stacked for a mid-range composite build, the anatomy looks like this:
Our Field Experience: 30 Deck Quotes in 2026
We quoted 30 residential decks this year out of our shop, and two 400 sq ft bids capture the realistic range of deck building cost per square foot. A pressure-treated build with a basic top rail and two steps closed at $6,900. The same footprint in composite, with four railing sections and a three-step entry, closed at $12,400 — dead center of the composite range above.
What moved prices between similar quotes had nothing to do with boards. Access matters — carrying materials through a house and over a fence costs hours. Slope matters: a 10 ft drop needs longer posts and extra bracing. A second-story deck adds fall-protection requirements and scaffolding. Demo an old deck first, and budget $800–$1,500 before the first new board goes down.
The deck you are quoted is only the deck you are building once it is itemized. Footings, railing, and stairs can each swing a 400 sq ft project by thousands.
DIY vs Hiring a Pro
Building it yourself drops the deck building cost per square foot to $4–$15 for materials only — a 400 sq ft PT deck you build yourself runs roughly $2,400–$3,200 in lumber and hardware. That is real money, and a simple design is genuinely buildable in a few weekends.
But the frame is not the DIY part. Joists, beams, and their connections carry the load, and an under-engineered frame fails silently for years before it fails dramatically. Inspectors check ledger flashing, joist spacing, and post-to-beam connections; a deck over 30 in. off grade is not a weekend experiment. If you DIY, do the decking and finish and hire a licensed contractor for the frame — our most common recommendation.
Hidden Costs Everyone Misses
- Demo and disposal: $800–$1,500 to tear out an old deck plus dump fees.
- Permits: $150–$600 depending on your city; most decks over 30 in. off grade require one.
- Inspection: usually rolled into the permit fee; a failed frame inspection costs a day of crew time.
- Stain or seal, year one: $300–$700 — skipping it voids the finish warranty and starts grain-checking.
- Furniture budget: a basic table-and-chairs set runs $800–$2,000.
If your deck sits over a living space, add a waterproofing membrane — a $1,000–$3,000 line item covered in our deck waterproofing guide.
Regional Pricing: Canada & New Zealand
| Market | 400 sq ft PT deck | 400 sq ft composite deck |
|---|---|---|
| Canada (CAD, ×1.35) | C$6,750–C$10,800 | C$12,150–C$20,250 |
| New Zealand (NZD, ×1.65) | NZ$8,250–NZ$13,200 | NZ$14,850–NZ$24,750 |
Those are straight currency conversions, and New Zealand prices skew to the top of the ranges: framing-grade radiata pine has been tight since 2022, and NZS 3604 bracing rules mean heavier framing than most US decks need. Canadian decks track US pricing closely, though treated lumber ships farther in the Atlantic provinces. APA — The Engineered Wood Association publishes the monthly lumber market data.
Frequently Asked Questions
How much does it cost to build a 400 sq ft deck?
A 400 sq ft deck costs $5,000–$8,000 in pressure-treated wood, $9,000–$15,000 in composite, or $11,000–$17,000 in PVC, fully installed. Add $1,500–$3,000 for footings on a challenging site and $150–$600 for permits.
How much does deck labor cost per square foot?
Deck labor cost per square foot runs $10–$18 for a licensed crew, covering framing and decking but not footings or site prep. Labor is typically 40–50% of the total deck cost, which is why DIY saves so much on paper.
Is it cheaper to build a deck yourself?
Yes, on materials: DIY runs $4–$15 per sq ft versus $20–$45 installed, and a 400 sq ft PT deck is about $2,400–$3,200. The catch is the frame — hire a licensed contractor for joists and beams, then DIY the boards and finish.
How much does a 20×20 deck cost?
A 20×20 deck is exactly 400 sq ft, so expect $5,000–$8,000 in wood, $9,000–$15,000 in composite, or $11,000–$17,000 in PVC installed. Railing adds roughly $1,500–$4,000 depending on material.
What’s the cheapest decking material?
Pressure-treated lumber is the cheapest: about $5–$6 per sq ft for the boards, or $12–$22 installed — roughly a third of a PVC deck’s total. Budget composite lines close the maintenance gap, but nothing beats PT on first cost.
Do I need a permit to build a deck?
Almost certainly, if the deck is over 30 in. off grade. Permits run $150–$600, and NADRA — the North American Deck & Railing Association — keeps code and safety resources for confirming local requirements. Skipping the permit can freeze a home sale later.
Sources
- Angi — deck installation cost guides
- NADRA — North American Deck & Railing Association
- APA — The Engineered Wood Association
- The Home Depot — lumber and decking pricing
