Rectangular 20×12 Deck Cost
A rectangular 20×12 (240 sqft) deck costs $12,000-$19,200 in mid-tier composite — about 0% more than the same size in a clean rectangle. A simple rectangular deck — the baseline build that anchors 75%+ of residential decks in the US. Lowest labor, lowest waste, fastest to permit.
5 finish tiers — rectangular 20×12
National $/sqft × rectangular shape's 1.00× complexity multiplier × 240 sqft = total installed cost. Materials + labor + standard railing included. Multiply by your state's labor multiplier for a local figure.
Excludes permit ($150-$450 typical), demolition (if replacing), site prep, and waste material premium. $7% waste factor already applied to material side of the tier $/sqft.
What changes vs a rectangular 20×12
When to pick rectangular
First-time builds, narrow yards, DIY projects, tight budgets, fast-permit jurisdictions.
Visually plain unless dressed up with railing detail, picture-frame trim, or pattern decking.
Open the calculator with rectangular 20×12 pre-loaded
Use the deck-cost calculator to dial in your exact material, railing, and stair specs. Set width and length directly.
FAQ — rectangular 20×12
How much does a rectangular 20×12 deck cost in 2026?▾
A rectangular 20×12 (240 sqft) deck costs $6,000-$9,600 in pressure-treated, $12,000-$19,200 in mid-range composite, and $18,000-$26,400 in luxury PVC. That's roughly 0% more than the same size in a rectangular shape — about $0 extra at mid-tier composite for the rectangular geometry. Numbers reflect 2026-Q1 national retail with average labor; multiply by your state's labor multiplier for a local estimate.
Why does a rectangular deck cost more than a rectangular one?▾
Standard ledger + 2-beam framing. Joists run perpendicular to the longer rim, hangers at 16″ OC. No unusual cuts in the perimeter. On top of that framing complexity, the material waste factor for rectangular is roughly 7% versus 7% for a clean rectangle — you'll order ~0% extra decking that ends up as offcuts. Combined, the labor multiplier on a rectangular build is about 1.00× rectangular baseline.
Is a rectangular deck right for a 20×12 footprint?▾
Best for: First-time builds, narrow yards, DIY projects, tight budgets, fast-permit jurisdictions. Watch-outs: Visually plain unless dressed up with railing detail, picture-frame trim, or pattern decking. At 240 sqft, a rectangular layout is balanced — fits the shape's typical sweet spot.
What framing changes for a rectangular vs rectangular?▾
Standard ledger + 2-beam framing. Joists run perpendicular to the longer rim, hangers at 16″ OC. No unusual cuts in the perimeter. For a 20×12 footprint specifically, plan for ~6 footings (vs ~6 for rectangular), and ~64 linear feet of perimeter (vs 64 for rectangular). Permit complexity is minimal — fastest review path.
How does rectangular affect long-term maintenance?▾
Easiest to clean, fastest to re-stain, fewest awkward corners for debris to collect in. Over a 25-year lifecycle, the maintenance delta vs rectangular adds roughly $0 — baseline for a 20×12 build. Composite reduces this delta by 60-80% — the more complex the shape, the more composite outperforms PT on TCO.