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A 8x12 deck covers 96 square feet and costs about $1,690 – $2,640 installed in pressure-treated pine, up to $3,686 – $5,760 in composite. It takes about 20 decking boards at 12 ft, 10 joists, 3 footings and 28 linear feet of railing.
| Material | Installed cost |
|---|---|
| Pressure-Treated Pine | $1,690 – $2,640 |
| Cedar | $2,458 – $3,840 |
| Redwood | $2,918 – $4,560 |
| Composite (Trex/TimberTech) | $3,686 – $5,760 |
| PVC / Cellular | $4,454 – $6,960 |
| Ipe / Tropical Hardwood | $4,992 – $7,800 |
A 8x12 deck is 96 square feet. In pressure-treated pine, expect roughly $1,690 – $2,640 installed. Cedar runs about $2,458 – $3,840 and composite about $3,686 – $5,760. 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 8 ft direction, you need 18 rows — that is 216 linear feet of decking, or about 20 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.