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A 12x12 deck covers 144 square feet and costs about $2,534 – $3,960 installed in pressure-treated pine, up to $5,530 – $8,640 in composite. It takes about 29 decking boards at 12 ft, 10 joists, 3 footings and 36 linear feet of railing.
| Material | Installed cost |
|---|---|
| Pressure-Treated Pine | $2,534 – $3,960 |
| Cedar | $3,686 – $5,760 |
| Redwood | $4,378 – $6,840 |
| Composite (Trex/TimberTech) | $5,530 – $8,640 |
| PVC / Cellular | $6,682 – $10,440 |
| Ipe / Tropical Hardwood | $7,488 – $11,700 |
A 12x12 deck is 144 square feet. In pressure-treated pine, expect roughly $2,534 – $3,960 installed. Cedar runs about $3,686 – $5,760 and composite about $5,530 – $8,640. Building it yourself typically removes 40 to 55 percent of those figures, because labour is around half of a finished deck price.
Laying boards across the 12 ft direction, you need 26 rows — that is 312 linear feet of decking, or about 29 boards at 12 ft with a waste allowance. A 12 ft board crosses the deck in one piece, so there are no butt joints.
About 3, one under each post, with posts at no more than 8 feet along the beam. That is roughly 0.37 cubic yards of concrete for 12 inch tubes poured 42 inches below grade — around 17 eighty-pound bags. Your own frost depth sets the real number and is not negotiable.