Price out deck boards at a lumber yard and a 12 by 16 foot deck looks like a weekend and a few hundred dollars. Then the quotes come back several times higher. The gap is not padding. Most of a deck's cost is in parts you will never look at again once it is built: the footings, posts, beams, joists and the connection to the house that keeps the whole thing standing.
HomeAdvisor puts deck labor alone at $15 to $35 per square foot, against $2 to $5 per square foot for pressure-treated decking boards.[1] This guide walks through where the rest of the money goes, using the American Wood Council's deck guide, which is based on the International Residential Code, so you know what to expect in a proper quote.
Key takeaways
- Footings must bear on undisturbed soil at least 12 inches deep or below the frost line, whichever is deeper.
- The ledger needs metal flashing, and the siding has to come off where it attaches; never attach a deck to brick veneer.
- Any deck more than 30 inches above grade needs a guard.
- Fasteners touching treated lumber must be hot-dip galvanized, stainless steel, silicon bronze or copper.
Below the deck: footings and posts
Every post sits on a concrete footing. The AWC guide requires footings to bear on undisturbed soil at least 12 inches below the ground surface or below the frost line, whichever is deeper, and tells builders to check the frost depth with the local building department.[2] In cold climates that can mean holes several feet deep. Posts in the guide are a minimum of 6x6.[2]
Soil matters as well. The guide expects the building official to check bearing conditions before concrete is poured, and weak soils change the footing design.[2] This is one reason two decks of the same size can have very different prices.
Where the deck meets the house
Most attached decks hang one side on a ledger board bolted to the house. It is the connection that fails most spectacularly when it is done badly, so the guide is specific: the ledger must be at least a 2x8, the house siding must be removed where it goes, and corrosion-resistant flashing is required wherever the ledger meets a wood-framed wall.[2] It also says, in capital letters, not to attach to brick veneer.[2]
Some houses can't carry a ledger, for example older homes with band boards thinner than an inch. Then the deck has to stand on its own posts or be designed by an engineer, which adds cost.[2]
The metal you pay for
Treated lumber corrodes ordinary steel. The guide requires screws, bolts, nails and washers used with preservative-treated wood to be hot-dip galvanized, stainless steel, silicon bronze or copper, and joist hangers and post anchors to be galvanized or stainless. Within 300 feet of salt water, fasteners and connectors must be grade 304 or 316 stainless.[2] Hangers, post bases and structural screws add up quickly on a large deck, and cheap substitutes are a common reason decks fail inspection.
Above the deck: guards and stairs
Every deck more than 30 inches above grade needs a guard.[2] Stairs need to be at least 36 inches wide, and any stair with four or more risers needs a handrail.[2] HomeAdvisor prices railings at $35 to $210 per linear foot, so a raised deck with a long perimeter can spend as much on railing as on decking.[1]
A cheaper shape
A deck built close to the ground avoids the guard requirement, needs shorter posts and fewer stairs. HomeAdvisor's average for ground-level decks is about $15 per square foot, against about $45 for second-story decks.[1]
When the standard rules don’t cover your deck
The AWC guide covers single-level wood decks attached to the house. Hot tubs and other heavy concentrated loads are outside its scope, and so are decks in areas with snow loads above 40 pounds per square foot.[2] In those cases expect engineered plans, which adds design fees and usually bigger framing.
Ask any builder whether their quote includes the permit, footing inspections and the final inspection. A deck built without them can become a problem when you sell the house.
Choosing the boards you actually walk on
Once the structure is right, the decking is the part you choose with your eyes, and it is also the part you maintain. Pressure-treated pine is the budget option and takes stain well, but it needs cleaning and sealing on a regular schedule and can check and splinter as it weathers. Cedar and redwood look warmer and resist decay naturally, at a higher price and with similar upkeep. Composite and PVC boards cost the most up front and mostly need washing, though they can get hot in full sun and each brand has its own rules for joist spacing.
That last point matters for the price. Some boards need joists closer together than others, which adds framing lumber and labor. Ask for the board choice to be settled before the framing is quoted, not after.
Sizing it for how you will use it
Most people size a deck by looking at the house. Try sizing it by the furniture instead. Set your outdoor table on the lawn, pull every chair back as if people were sitting in them, and add enough room to walk around the outside. Do the same for the grill, leaving the clearance its manual asks for, and for any loungers. That outline is the smallest deck that will feel comfortable.
Two more checks: make sure a door opening onto the deck doesn’t swing into the main walkway, and look at where the sun is in the late afternoon, when most people use a deck. A shady corner may be worth more than extra square feet.
What the permit process looks like
Building departments usually want a simple drawing before they issue a deck permit: where the footings go, the size and spacing of joists and beams, how the ledger is attached and flashed, and the guard and stair details. Many accept the AWC guide’s prescriptive tables as the basis for that drawing, which saves paying for an engineer on a straightforward deck.
Inspections tend to come at three points: the footing holes before concrete goes in, the framing before the boards hide it, and a final once the guards and stairs are done. Plan the schedule around them. A crew that has to wait for a footing inspection is not a crew doing anything wrong.
A ten-minute check every spring
Decks age quietly, so make a short inspection part of spring cleanup. Look under the deck at the ledger for rust streaks or rot, and check that the flashing is still in place. Push on every guard post; any movement is worth fixing before someone leans on it. Probe posts where they meet the footing, sweep debris out of the gaps between boards so water can drain, and replace any popped screws or nails.
Plug your house size, land price and quotes into the free calculator. It uses the same NAHB 2024 averages as this guide.
Frequently asked questions
Why is building a deck so expensive?
Most of the cost is structure and labor: footings below the frost line, posts, beams, joists, a flashed ledger, code-required guards and stairs, and corrosion-resistant hardware. HomeAdvisor puts labor alone at $15 to $35 per square foot.
Does a deck need a railing?
Under the AWC deck guide, which follows the International Residential Code, any deck more than 30 inches above grade needs a guard.
Can I attach a deck to a brick house?
Not to brick veneer. The AWC guide says not to attach a ledger to brick veneer; the deck needs its own support instead.
Do I need a permit to build a deck?
Usually, especially for decks attached to the house or raised off the ground. Expect to submit a drawing and to have the footings, framing and finished deck inspected.
How big should my deck be?
Lay out your table with the chairs pulled back, the grill with its required clearance and any loungers, then add room to walk around them. That outline is the smallest comfortable size.
Sources
- HomeAdvisor, "How Much Does It Cost to Build a Deck?", updated June 17, 2026 Verified
- American Wood Council, "Prescriptive Residential Wood Deck Construction Guide" (DCA 6), based on the 2015 IRC Verified
Figures last checked October 19, 2026. National averages are a planning guide, not a quote. See our editorial policy and data sources.
