A 12x12 deck of pressure-treated pine costs about $8,500 built by a contractor at US-average prices ($5,100 to $11,800), which is $59 per square foot for 144.00000000000003 sq ft. Doing the work yourself leaves materials of about $3,050.
A 12x12 deck seats a four-person table with chairs pulled out, or a grill and a pair of lounge chairs, without one corner turning into storage.
12x12 deck cost by decking material
The same frame, footings, railing and steps, priced with three decking grades at US-average prices (HomeAdvisor, June 2026; Fixr, January 2023). The frame is always pressure-treated pine; only the boards change.
| Decking | Materials only | Built by a contractor | Typical per sq ft | Crew days |
|---|---|---|---|---|
| Pressure-treated pine | $1,550 to $4,550 | $5,100 to $11,800 (typical $8,500) | $59 | 5 |
| Cedar | $1,700 to $4,850 | $5,200 to $12,100 (typical $8,700) | $60 | 5 |
| Composite | $3,000 to $7,000 | $6,500 to $14,300 (typical $10,400) | $72 | 5 |
Every row includes a 3-footing foundation, a wood railing on 33 ft of open edge, 5 steps down from a 3 ft high deck and a building permit. Labor is HomeAdvisor's $15 to $35 per square foot, $25 typical. Your state moves the totals by its own wage and materials level, which the calculator above applies.
Material list for a 12x12 deck
The list below is the 12x12 deck as the framing engine lays it out: attached to the house with a ledger, 40 psf live load, Southern pine, 1,500 psf soil, 6×6 posts, 10 percent spare boards.
| Item | Quantity | Detail |
|---|---|---|
| 5/4 × 6 wood deck board (1 × 5½ in) | 29 boards | 12 ft long |
| Deck screws, No. 8 | 520 screws | 2 per board at every joist (IRC R507.7) |
| 2×8 joists | 10 pcs | 12 ft, cut to 12 ft |
| 2×8 rim joist | 1 pcs | 12 ft |
| 2×8 ledger board, treated | 1 pcs | 12 ft (at least 2×8, R507.9.1.1) |
| 2×8 for the beam | 2 pcs | 12 ft, 2 plies spliced only over posts |
| 6×6 posts, ground-contact treated | 1 pcs | 8 ft, cut to 1 ft 8 ½ in each (3 posts) |
| Post bases for 6×6 | 3 pcs | galvanized (ZMAX) or stainless |
| Post-to-beam connectors | 3 pcs | or notched posts with two ½ in bolts (R507.5.2) |
| Joist hangers for 2×8 | 10 pcs | one per joist at the ledger |
| Joist-to-beam ties | 10 pcs | one per joist at each beam |
| ½ in lag screws with washers | 10 pcs | staggered, 16.5 in on center (Table R507.9.1.3(1)) |
| Concrete mix, 80 lb bag | 6 bags | 2.9 cu ft for 3 footings |
| Tube forms, 10 in | 3 pcs | one per footing |
Cedar uses the same board count as pressure-treated pine (29 boards including spares). Composite changes the decking lines to 29 boards in 12, 16 or 20 ft lengths plus 270 hidden clips, and needs no deck stain, which the wood grades do. The deck board calculator shows the board layout row by row, and the deck calculator lets you change spacing, board width and pattern.
Framing for a 12x12 deck
With joists running the 12 ft width, the tables in IRC 2024 R507.6 select 2×8 joists at 16 in on center, 10 of them for the 12 ft length. The beam is a double 2×8 on 3 posts spaced 6 ft apart (R507.5), each on a round footing about 16 in across (R507.3.1). The footing depth depends on your frost line, so check the deck footing calculator with your local depth, and the deck joist span table if you want a different lumber size.
Labor and time
Labor comes to $5,400 at the typical rate. At $70 an hour for each of two builders working eight hours, one crew day is $1,100, so the job is about 5 days of work for a two-person crew, not counting waiting for footings to cure or for the inspector. Add 5 stair steps with the stair calculator and the stringer layout is done before the boards arrive.
Does a 12x12 deck need a permit?
Under IRC 2024 R105.2 a deck is exempt from a permit only if it is no more than 200 sq ft, no more than 30 in above grade at any point, not attached to a dwelling and not serving the required exit door. A 12x12 deck is 144 sq ft, so the area test is met. This page assumes the usual case, a deck bolted to the house 3 ft off the ground, which fails the attachment and height tests: 36 in above grade is over the 30 in limit; a deck attached to the house is never exempt. Budget the permit ($230 to $500 per HomeAdvisor) and the inspections. Many towns are stricter than the model code, so call the building department before you buy lumber.
12x12 deck compared with other sizes
Stepping down to 10x10 saves 44 sq ft and about $2,100 at the typical price. Stepping up to 12x16 adds 48 sq ft and about $1,900. Cost per square foot falls a little as the deck grows because the stairs, permit and ledger are fixed costs.
Next steps for a 12x12 deck
- Size every joist, beam and footing for a 12 by 12 ft deck in the deck calculator.
- Count boards by stock length with the decking calculator.
- Price a different shape, height or railing in the deck cost calculator.
- Add up the footings' concrete with the concrete bag calculator, and the finish with the deck stain calculator.
- Prices for every size are grouped in cost calculators.