How much does it cost to build a deck?
Start with deck area, keep material and labor rates separate, then add railing, permits, delivery, site work, and a contingency instead of hiding everything inside one square-foot price.
20 × 16 ft deck
320 square feet
The deck-cost formula
For a 20 × 16 ft deck, use $18 per square foot for materials, $22 per square foot for labor, $2,500 for railing, and $500 for permits and miscellaneous costs:
These are example inputs, not a market quote. Replace every rate with a supplier price or contractor allowance that matches the design and your location.
Budget scenarios for the same deck
| Scenario | Materials | Labor | Railing + other | Planning total |
|---|---|---|---|---|
| Lean allowance | $14/ft² | $16/ft² | $2,000 | $11,600 |
| Worked example | $18/ft² | $22/ft² | $3,000 | $15,800 |
| Higher allowance | $28/ft² | $30/ft² | $5,000 | $23,560 |
Scenario totals illustrate the calculator formula. They do not represent guaranteed local prices.
Costs commonly missed
Deck boards are only one part of the project. A usable budget may also need footings, posts, beams, joists, blocking, ledger work, approved connectors and fasteners, stairs, guards, handrails, demolition, disposal, delivery, permits, inspections, and site access. Roofs, hot tubs, kitchens, unusual loads, and second-story conditions can change the structural design substantially.
Keep an explicit contingency rather than lowering the material quantity. This makes it easier to see whether a change came from scope, pricing, or waste.
Structure and code come before price
The American Wood Council’s DCA 6 is a prescriptive reference for certain single-level residential wood decks attached to a house. Its tables and connection details have defined limits; it is not a universal design for every deck. Local code adoption, frost depth, snow and wind loads, soil, existing construction, and proprietary products can require different details or professional design.
- Sketch the exact footprint. Mark stairs, doors, posts, and changes in elevation.
- Confirm structural scope. Identify whether the deck is attached or freestanding and whether unusual loads are planned.
- Price a complete material list. Include framing, connectors, guards, stairs, finishes, delivery, and tax.
- Separate labor and allowances. Ask what demolition, permit handling, and cleanup include.
- Verify before construction. Obtain required approvals and inspections.
Frequently asked questions
Should I use cost per square foot?
It is useful for an early comparison, but it should be split into material and labor rates and supplemented with fixed costs. Two decks with the same area can have very different railing, stair, footing, access, and structural requirements.
Does the calculator include regional pricing?
The deck calculator uses the rates you enter. For the best local estimate, replace its defaults with current supplier and contractor figures rather than treating a national average as a quote.
How much contingency should I include?
There is no universal percentage. Base it on how complete the design and quotes are, plus the likelihood of hidden site or demolition conditions.