Deck cost

Building a deck costs $30 to $100 per square foot installed, so a 300 square foot deck is $9,000 to $30,000. Pressure-treated wood runs $30 to $65 per square foot and composite $40 to $100.

The board is the part everyone shops for and the smallest part of the price. On a composite deck the boards are $9 to $16 per square foot. Everything else, footings, frame, hardware, railing, stairs and labor, is the other two thirds.

Cost by material

Those figures include the substructure, railing and one set of steps. A deck one step off the ground on level land is at the bottom. A deck ten feet up on a sloped lot, with deep footings, tall posts, a long stair run and a landing, is at the top of the range or beyond it.

Cost by deck size

Composite, ground level, at the typical rate:

Height matters more than area beyond a point. A deck more than about 30 inches off the ground needs guard rails to code, and above roughly 6 feet it needs larger footings, bracing, and often an engineer's stamp.

Wood against composite, honestly

Pressure-treated wood is a third to a half cheaper up front. It needs cleaning and re-staining every two to three years, which is $500 to $1,500 done professionally or a weekend of your own time. It lasts 10 to 15 years before boards start to cup, split and need replacing.

Composite costs more and needs washing, not staining. Modern capped composite resists fading and staining well and carries 25 to 50 year warranties on the boards. It gets hot in direct sun, noticeably hotter than wood, which matters if anyone walks on it barefoot in July. Dark colors are worse.

Over twenty-five years composite is cheaper, once you count the staining. Over seven years it is not. The decision is really about how long you plan to own the house and whether you will actually do the maintenance.

Cedar and redwood sit between them, look better than treated pine, and still need finishing.

The substructure is the deck

The frame is what fails, and it is invisible once the boards are down.

• Footings below the local frost line. This is the most commonly cut corner and the reason decks heave and sag.
• Ledger attachment to the house, through-bolted with proper flashing. Improperly attached ledgers are the leading cause of deck collapse, and they fail all at once, usually with people standing on the deck.
• Joist tape over the top of each joist, which keeps water out of the fastener holes. It costs a few hundred dollars and adds years.
• Galvanized or stainless hardware, because treated lumber corrodes ordinary steel.

Ask specifically about the ledger and the footings. A contractor who answers confidently is worth more than one who is cheaper.

What else lands on the quote

• Stairs: $150 to $400 per step
• Railing: $60 to $200 per linear foot, cable and glass at the top
• Built-in bench seating: $80 to $200 per linear foot
• Deck lighting: $80 to $250 per fixture
• Removing an old deck: $500 to $2,000
• Permit: $150 to $600
• Pergola over part of it: $20 to $65 per square foot

Railing is the line people underestimate. On a small deck it can be a quarter of the project, because a 10 by 12 deck has 32 feet of perimeter to guard.

Do you need a permit

Almost always, for anything attached to the house or more than about 30 inches high. A deck is a structure people stand on in numbers, and it is inspected for exactly that reason.

Unpermitted decks are a routine finding at sale, and an unpermitted deck that fails is a serious insurance problem. The permit is $150 to $600 and it buys an inspection of the footings and the ledger, which are the two things you cannot see afterwards.

Go deeper

Decks

• Composite deck cost, and re-decking an existing frame
• Deck cost by state, built from Bureau of Labor Statistics wage data
• Deck railing cost, often a third of a small deck
• Deck repair cost, and why the ledger is the safety issue
• Deck staining cost, where the preparation is the job
• How long does a deck last

Patios and hard surfaces

• Paver patio cost, the cheaper way to get outdoor space
• Concrete patio cost, and why the base is everything

Driveways

• Concrete driveway cost
• Asphalt driveway cost, and how it compares
• Gravel driveway cost, and the maintenance nobody mentions
• Driveway repair cost, and fixing the water first

Structures

• Pergola cost
• Patio cover cost, attached against freestanding
• Fence installation cost per linear foot
• Outdoor kitchen cost, and what has to be rated for outdoors
• Fire pit cost, and the clearances that matter

Pools

• Inground pool cost, including the running cost
• Above ground pool cost

Garden and grounds

Lawns, planting, trees, irrigation and retaining walls have their own section, starting with landscaping cost and where the money actually goes.

Frequently asked questions

How long does a deck take to build?

One to two weeks for a straightforward ground-level deck, three to four for an elevated one with stairs and complex railing. Permit and inspection scheduling usually adds two to four weeks before work starts.

Does a deck add value?

Wood decks recover roughly 50% to 65% of their cost at resale and composite somewhat less, though composite is more attractive to buyers who do not want maintenance. Neither is an investment; both make a house more pleasant to live in.

Can I build it myself?

A ground-level, freestanding deck is a realistic ambitious-DIY project and saves roughly 40% of the cost. Anything attached to the house or elevated is not, because the ledger and the footings are the two details that hurt people when they are wrong.

How long does a deck last?

Ten to fifteen years for treated wood, twenty-five to fifty for composite boards. The frame usually outlasts the boards, so re-decking an existing sound frame is a real and much cheaper option at $20 to $45 per square foot.

What is the cheapest way to get more outdoor space?

A patio at ground level. Concrete is $8 to $26 per square foot and pavers $12 to $30, against $30 to $100 for a deck, because there is no structure to build.