How we estimate deck building cost
Every estimate combines a national price for each part of the job with a local labor adjustment for your state. Here is exactly how that works and where the numbers come from.
The formula
For each line item we multiply a quantity (driven by the deck's size, the decking material, whether it is ground-level or raised, and whether it includes perimeter railing and a stair run) by a national unit cost, then apply a quality-grade factor. A regional labor multiplier is applied to the labor portion only — materials are priced nationally. We show the itemized result as a ±25% range.
National unit costs
| Line item | National unit cost | Source |
|---|---|---|
| Substructure (footings, beams & joists) | $9.00 / sq ft | ref |
| Decking boards | $13.00 / sq ft | ref |
| Build labor | $6.00 / sq ft | ref |
| Railing | $30.00 / sq ft | ref |
| Stair run | $900.00 / sq ft | ref |
Regional labor multipliers
Each state's labor multiplier is its mean carpenter wage relative to the national mean, from the U.S. Bureau of Labor Statistics Occupational Employment & Wage Statistics (Carpenters, SOC 47-2031) — decks are framed and built by carpenters, so this is the direct trade wage. Multipliers are bounded to a sane range and applied to the labor share of each line item, so materials stay nationally priced while labor tracks local wages.
Data vintage & limitations
Compiled June 2026 from public cost aggregators and government wage data — these are derived estimates, not live contractor quotes. Local prices vary with project complexity, access, and material availability; always confirm with a licensed contractor before budgeting.
Sources
- https://funoutdoorliving.com/deck/cost-to-build-composite-deck/
- https://taxfoundation.org/data/all/state/sales-tax-rates-midyear-2025/
- https://www.bls.gov/ooh/construction-and-extraction/carpenters.htm
- https://www.decks.com/resource-index/decking/composite-decking-price-comparison/
- https://www.homeadvisor.com/cost/stairs-and-railings/deck-railing/
- https://www.premiumdeckingsupply.com/deck-replacement-cost/
- https://www.pro-mapper.com/decking/how-much-does-it-cost-to-build-a-deck/