Calculate the estimated cost to build a deck — footings, framing, decking, railing, stairs, and labor — with an itemized breakdown. National average cost: $4000–$22000 per sq ft. Enter your project size below for an itemized breakdown — adjust any line item to match your local prices and scope.
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Try Suparate FreeThe ledger connection is the most critical detail on an attached deck
Ledger failures cause the majority of serious deck collapses. The ledger must be fastened with code-approved structural screws into solid framing (not siding or sheathing), and proper flashing must be installed to prevent water intrusion behind the ledger. This is not an area to cut corners — have it inspected before framing any further.
Dig footings below your local frost depth
Footings that don't extend below the frost line will heave in winter, shifting and racking the entire deck structure. Frost depth ranges from 12 inches in the Deep South to 60 inches in Minnesota. Look up your local frost depth or call the building department — this is the one spec that most DIY deck builders get wrong.
Pre-stain deck boards before installation
Applying stain or sealant to the bottom and edges of deck boards before installation protects the side grain that is most vulnerable to moisture intrusion. This doubles the protection of end cuts and the board's undersurface — areas you can't reach once the deck is built. Takes 30 minutes extra and adds years to the deck's life.
A pressure-treated wood deck costs $15–$35 per sq ft installed. A 16×20 ft deck (320 sq ft) runs $5,000–$11,000 for basic PT lumber. Composite decking (Trex, TimberTech) costs $35–$60 per sq ft installed and has lower maintenance costs over its lifetime. Elevated decks with complex framing, multiple levels, or built-in features like pergolas and benches cost significantly more.
Most jurisdictions require a permit for any attached deck or any freestanding deck over 200 sq ft and/or 30 inches above grade. Permits ensure footings are designed for your soil and frost conditions, the ledger connection is waterproofed and structurally sound, and railing heights meet code. An unpermitted deck is a liability at resale and can be required to be removed.
Pressure-treated wood decks last 15–25 years with annual cleaning and staining every 2–3 years. Composite decking (Trex, Fiberon) carries 25–30 year warranties and requires minimal maintenance — occasional washing only. Cedar and redwood last 15–20 years and look better naturally but require the same maintenance schedule as PT lumber. Footings and structural framing outlast the decking and can be reused when decking is replaced.
PT wood is 30–50% cheaper upfront but requires sanding and staining every 2–3 years and will eventually warp, splinter, and rot. Composite decking costs more initially but has a 25–30 year warranty, requires almost no maintenance, and holds its appearance much longer. For clients who want to install and forget, composite is the better long-term value. For clients optimizing upfront cost, PT lumber is the choice.
An attached deck connects to the house via a ledger board fastened to the rim joist or band joist. A freestanding deck stands independently on its own post-and-beam system. Freestanding decks require more footings and framing but are structurally safer in cases where the house framing is not accessible or where attaching would compromise waterproofing. Many local codes now require freestanding construction in specific scenarios.
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