Deck cost per square foot — pressure-treated, cedar and composite

Decking is the one outdoor project where the material decision changes the price by a factor of two and the maintenance by a factor of ten. It is also the one where the quote you receive covers a structure you cannot see, which makes it worth understanding what is under the boards before you compare numbers.

What the three materials actually cost

A caution before the table. Decking cost figures come almost entirely from cost-aggregator sites rather than trade associations, and they are inconsistent in what they include. I have flagged the specific inconsistency below rather than smoothing it over.

The note: HomeGuide lists pressure-treated "materials" at $10–$20 per square foot, which is above the cedar materials figure from Angi. That cannot be right for the cheaper wood, and the likeliest explanation is that the PT number bundles framing, fasteners and substructure while the cedar number is deck boards alone. So I will not publish a PT material-only figure — it would be comparing two different things and telling you PT costs more than cedar, which it does not.

What you can take from the table with confidence is the shape: cedar has the lowest installed floor, composite has the longest life, and pressure-treated is the cheapest board with the shortest life and the most upkeep.

The ten-year arithmetic

Sticker price is the wrong comparison, and this is where most people's instinct fails them.

Take a 320 square-foot deck (16 × 20), and use the mid-point of each installed range:

Cedar wins on ten years. Composite wins on twenty-five. Pressure-treated wins only if you are selling the house — which is a completely legitimate reason to choose it, just not the same reason as "it's cheaper."

The sealing figure is where wood quietly gets expensive, and it is not only money. Sealing a deck is a weekend, every two or three years, forever. Some people do not mind. Most people mean to and do not, which is why so many pressure-treated decks are gray and splitting at year eight rather than year eighteen.

What is under the boards

The part nobody quotes until you ask, and the part that actually decides whether a deck lasts.

Joist spacing. Trex specifies composite decking at no more than 16 inches on center for standard applications, and 12 inches for a 45-degree diagonal layout. Twelve inches or tighter is also required for heavier loads, longer spans and intricate patterns, and stair stringers are usually 12 inches or less. Note that it is the diagonal layout driving the 12-inch rule rather than composite as a material — though some PVC and low-density composite lines specify 12 inches even running straight, so the product's own installation instructions are the authority, not a rule of thumb.

This matters commercially: a diagonal deck needs a third more framing lumber and a third more labor to build the frame. That is a real cost difference for a purely aesthetic choice, and it should be a decision you made knowingly.

Board coverage. A 5/4 × 6 deck board is nominally six inches wide and actually 5½ inches. With a standard ¼-inch gap, each board occupies 5¾ inches of width, so one linear foot of board covers about 0.479 square feet — meaning you need roughly 2.09 linear feet of board per square foot of deck, before waste. The decking calculator does this board math for you and adds 10% for waste.

For that 320 square-foot deck: about 669 linear feet of decking, or 736 feet with 10% waste. In 12-foot boards, that is 62 boards. Worth knowing before someone hands you a materials list.

A rough framing take-off. For a 16 × 20 deck with joists spanning the 16-foot direction at 16 inches on center:

Where the money actually goes

Two decks of identical size and identical material can differ by 60%, and the reasons are structural rather than cosmetic:

Height. A deck 18 inches off the ground and a deck 9 feet off the ground are different projects. The second needs deeper footings, taller posts, bracing, guard rails to code, and stairs — often several thousand dollars of difference before a single deck board.

Stairs. The most labor-intensive part of any deck per square foot. A long run to grade can cost as much as a substantial section of the deck itself.

Railings. Frequently 20 to 30% of a deck's cost. Composite and cable railings run far above pressure-treated pickets.

Access. A backyard reachable only through a gate means everything is carried. That shows up in labor hours whatever the material.

Ledger or freestanding. Attaching to the house is cheaper but demands correct flashing — a badly flashed ledger is the single most common cause of both deck failures and rot in the house's rim joist.

Frequently asked

Is composite slippery or hot? Modern composite is textured and no worse than wet wood. It does run hotter in direct sun, noticeably so in dark colors — worth thinking about for a south-facing deck people walk on barefoot.

Can I put composite on my existing frame? Only if the joist spacing and the frame's condition suit it. Old frames are often 24 inches on center, which no composite manufacturer permits, and adding joists to an existing frame is real work.

Is cedar worth it over pressure-treated? On appearance and stability, generally yes. It still needs the same sealing schedule, so the maintenance argument is a wash — the argument is that it looks better doing it.

Do I need a permit? In most Western New York municipalities, yes, for anything attached or above a certain height. Get it. An unpermitted deck becomes a problem at closing.

Run your own numbers

Trace the deck footprint on the aerial view, choose Decking — build under Area, and it returns square footage, an installed range, the do-it-yourself material figure, and a rough framing list — joist count at 16 inches on center, ledger, rim, hangers and board count against a board length you pick. It also gives the material weight, which matters if you are hauling it yourself.

Sources: HomeGuide — pressure-treated decking cost · Angi — cedar decking prices, July 2026 · Composite Deck Direct — composite decking cost guide, May 2026 · Trex — how to install deck joists · 5/4 × 6 actual dimensions from retailer product specifications

Educational use. Cost figures come from cost-aggregator sites, not a survey, and are not a bid. Framing quantities exclude footings, beams, posts, stairs and railings — all of which are governed by local code and, where applicable, an engineer's design.