Uniform worksheet · Home Improvement
Form RET-210 · Effective August 2026 · Borrower’s copy
Deck Cost Calculator
Estimate materials and labor cost for a new deck.
Deck Dimensions
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Deck Area
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Materials
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Total Estimated Cost
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Cost Breakdown
How to Use This Deck Cost Calculator
See MethodologyOur free deck cost calculator estimates the total cost of building a new deck, including materials and optional labor. Enter your dimensions for a detailed cost breakdown.
Deck costs depend on size, materials, and complexity. Wood: $15-$25/sq ft DIY. Composite: $30-$60/sq ft.
Includes structural components: footings, posts, joists, and decking boards. Budget an additional 15-20% for hardware.
Attached vs. freestanding decks have different structural requirements. An attached deck requires a ledger board bolted to the house rim joist, with step-flashing or membrane flashing installed behind the siding to prevent water intrusion — this connection is the most common failure point in deck construction. Freestanding decks avoid this risk entirely and may not require a building permit in some jurisdictions.
Joist spacing is critical for structural integrity and decking performance. Standard spacing is 16 inches on center for most decking materials, though 12-inch spacing is recommended for composite and PVC boards to prevent sagging between joists. All joists should be hung with joist hangers — never toe-nailed — and blocking or bridging should be installed at mid-span for joists over 8 feet long.
Footing depth must extend below the local frost line, which varies from 12 inches in southern states to 48 inches or more in northern regions. Check your local building code for the exact depth, and pour concrete footings in bell-shaped forms for maximum bearing capacity. Railing code requires a minimum height of 36 inches for decks over 30 inches above grade, with balusters spaced no more than 4 inches apart to prevent child entrapment.
Always obtain a building permit and schedule required inspections — footings, framing, and final. Unpermitted decks can create serious problems during a home sale and may void your homeowner's insurance. Over a 10-30 year timeframe, composite vs. wood maintenance costs diverge significantly: pressure-treated wood needs staining every 2-3 years ($300-$500 per application), while composite requires only soap-and-water cleaning, potentially saving thousands over the deck's lifetime.
Related Topics
Frequently Asked Questions about Deck Building Costs
How much does it cost to build a deck?
DIY pressure-treated wood runs $15–$25 per square foot, professional installation is $30–$50/sq ft, and composite decking ranges from $30–$60/sq ft. A typical 16×20 deck (320 sq ft) costs roughly $5,000–$25,000 depending on materials, railing, stairs, and whether it's freestanding or attached to the house.
How many footings do I need?
Footings should be placed every 6–8 feet along each joist span, with a minimum of one footing per 6 feet of beam length. A 16×20 deck typically requires 6–9 footings, each dug 42–48 inches deep or below your local frost line to prevent heaving. Attached decks also need a ledger board with proper flashing at the house connection.
Is composite decking worth it?
Composite costs 2–3 times more upfront than pressure-treated wood, but it never needs staining, sealing, or sanding. Over a 20–30 year period, the total cost of ownership — factoring in zero maintenance — is often lower than wood. Composite also resists warping, splintering, and insect damage.
Do I need a permit to build a deck?
Most jurisdictions require building permits for decks over 200 square feet, any deck attached to the house, or structures above a certain height — typically 30 inches above grade. Permit costs range from $50 to $500 depending on your location, and inspections are usually required at the footing and final stages. Always check local building codes and HOA rules before starting.
How do I calculate lumber for a deck?
Decking boards require the total area plus 10% waste divided by the board's coverage width. Joists are spaced 16 inches on center, so divide the deck width by 1.33 feet and add 1 for the end joist. Our calculator handles the material counts, but you'll also need ledger boards, beams, posts, and hardware — budget an additional 15–20% beyond decking costs alone.
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