Deck Cost Calculator

How Much Does a Deck Cost?

A 16 × 12 ft treated-wood deck 4 ft off the ground costs about $6,218 built, with a railing on three sides and a permit: $32.39 a sq ft. With composite boards and railing, the same deck comes to $9,268, $48.27 a sq ft.

Deck cost by size, 4 ft high, installed with railing and a permit:

Cost per square foot falls as the deck grows, because the railing and the permit don't grow with the area:

What Goes Into the Price

Each line of the cost, for the default 16 × 12 ft deck:

The framing comes from the IRC deck tables: thirteen 2x10 joists 16 in on center, a doubled 2x10 beam on three 6x6 posts and three 18 in round footings. It is the same under wood and composite boards, since both span 16 in between joists. Here is what each line buys:

Every price in the calculator can be changed with a click, and the total follows. For the lumber, hangers, lag screws and concrete bags line by line, count the deck materials.

How to Calculate Deck Cost

Add the materials, the installation by the square foot, the railing by the foot of open edge and the permit:

The railing runs along the front and both sides; the house side needs none. Decks 30 in or less above grade don't need a guard by code (IRC R312.1), and without one the default wood deck comes to $4,618.

Composite vs. Wood Deck Cost

Composite adds $3,050 to the default deck, about 49% more. The boards account for less of that than you might expect:

• Railing: +$1,600, the biggest part, at $80 a foot installed against $40 for wood.
• Installation: +$960, at $20 a sq ft against $15.
• Boards: +$362 for 29 boards at $30.99 against $18.50.
• Fasteners: +$128, hidden clips instead of face screws.

The framing stays the same: Trex rates its standard 1x6 boards for joists 16 in on center, the same as 5/4 wood. Board lines differ a lot in price. A 16 ft board costs $30.99 in Trex Enhance, $52.49 in Trex Select and $66.55 in TimberTech Legacy; count the composite boards for your deck.

What Changes the Cost of a Deck

• Size: the larger the deck, the lower the cost per square foot, from $39.62 on a 10 × 10 ft deck to $30.11 on 24 × 16 ft in wood.
• Depth: a deeper deck needs bigger joists and a bigger beam. Past 16 ft 6 in from the house, even a southern pine 2x12 can't span it, and the deck needs a second beam.
• Height: posts cost little, but a deck more than 30 in up needs a guard, and a high deck needs a longer stair; price the stair on its own.
• Railing style: a wood guard built on site costs least; kits and composite or metal systems cost more. You can price the railing both ways.
• Footings: where the frost line is deep, footings go deeper and take more concrete.
• The site: removing an old deck, a slope, poor access or a hot tub, which needs its own engineered framing, all add to the bill.

Stairs, Lights and Other Extras

The calculator prices the deck, its railing and the permit. A few things most decks also need are priced elsewhere:

• Stairs: a deck 4 ft up needs 7 risers and 6 treads. The stringers and tread boards of a 36 in wide stair cost about $116, plus a handrail and a footing at the bottom.
• A light at the stairs: the IRC asks for a light at the top landing of exterior stairs (R303.7), switched from inside.
• Benches and planters: built-in seats along the edge change the guard, which is then measured from the seat (DCA 6).
• A hot tub: its weight is far beyond the 40 psf a deck is framed for, and DCA 6 leaves such loads to an engineer.

Ways to Keep the Cost Down

• Size the deck to the lumber. Deck boards come in set lengths, so a 16 ft deck uses whole 16 ft boards, while a 17 ft deck needs 20 ft boards or a joint in every row.
• Keep it rectangular. Angles, curves and inside corners add cuts, blocking and waste, and the railing gets more posts.
• Mix materials. Composite boards sit on the same treated framing as wood, so you can put the money where you walk and touch.
• Choose the railing with care. On the default deck, the railing costs more than the deck boards in both wood and composite.
• Build the guard and stairs yourself. They are repetitive work, and the materials for a wood guard on three sides come to about $481.

Re-Decking an Old Frame

If the joists, beam, posts and ledger are sound and meet the code, you can replace only the boards. On the default deck, new boards and fasteners cost $570 in treated wood or $1,060 in composite, before labor and removing the old boards.

Check the frame first: the ledger has to be lagged or bolted and flashed, not nailed, and joists spaced for the new boards. Composite boards need joists 16 in on center or closer; an old wood deck on 24 in joists for 2x6 boards needs extra joists before composite goes on.

For a deck at ground level, a patio may cost less; compare the cost of a concrete slab.

Building It Yourself

Doing the work yourself leaves the materials and the permit. For the default deck that is about $2,219: $1,438 for the framing, decking and hardware, $481 for a wood guard of 2x2 balusters, 2x4 rails and a 2x6 cap, and the $300 permit. Against $6,218 built, the labor and the contractor's railing make up the difference.

The parts the code cares most about are structural: the ledger fasteners and flashing, footing depth, beam and joist sizes, and the guard posts. The AWC's prescriptive guide, DCA 6, shows code-compliant details for a typical deck and is a good reference for planning one.