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A 16x20 deck covers 320 square feet and costs about $5,632 – $8,800 installed in pressure-treated pine, up to $12,288 – $19,200 in composite. It takes about 38 decking boards at 20 ft, 16 joists, 4 footings and 52 linear feet of railing.
| Material | Installed cost |
|---|---|
| Pressure-Treated Pine | $5,632 – $8,800 |
| Cedar | $8,192 – $12,800 |
| Redwood | $9,728 – $15,200 |
| Composite (Trex/TimberTech) | $12,288 – $19,200 |
| PVC / Cellular | $14,848 – $23,200 |
| Ipe / Tropical Hardwood | $16,640 – $26,000 |
A 16x20 deck is 320 square feet. In pressure-treated pine, expect roughly $5,632 – $8,800 installed. Cedar runs about $8,192 – $12,800 and composite about $12,288 – $19,200. 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 16 ft direction, you need 35 rows — that is 700 linear feet of decking, or about 38 boards at 20 ft with a waste allowance. A 20 ft board crosses the deck in one piece, so there are no butt joints.
About 4, one under each post, with posts at no more than 8 feet along the beam. That is roughly 0.49 cubic yards of concrete for 12 inch tubes poured 42 inches below grade — around 23 eighty-pound bags. Your own frost depth sets the real number and is not negotiable.