Reference

Materials for common deck sizes

Pick a size for its full takeoff: boards by length, screws or clips, joists, beam, footings and concrete. Sizes read “out from the house × along the house”.

Composite boards at a glance

Size	Area	Buy (12/16/20 ft)	Boards	Offcut waste
8×8 deck	64 ft²	8×20′ + 2×12′	10	10.8%
8×10 deck	80 ft²	6×20′ + 5×16′ + 1×12′	12	5.1%
8×12 deck	96 ft²	12×20′ + 1×12′	13	5.9%
10×10 deck	100 ft²	7×20′ + 6×16′ + 2×12′	15	7.2%
10×12 deck	120 ft²	15×20′ + 1×12′	16	8.6%
10×14 deck	140 ft²	9×20′ + 15×12′	24	7.5%
10×16 deck	160 ft²	16×20′ + 9×12′	25	8.6%
10×20 deck	200 ft²	7×20′ + 8×16′ + 20×12′	35	8.5%
12×12 deck	144 ft²	17×20′ + 2×12′	19	8.4%
12×14 deck	168 ft²	10×20′ + 1×16′ + 17×12′	28	7.3%
12×16 deck	192 ft²	19×20′ + 1×16′ + 9×12′	29	9.6%
12×18 deck	216 ft²	28×20′	28	9.4%
12×20 deck	240 ft²	8×20′ + 10×16′ + 23×12′	41	8.5%
12×24 deck	288 ft²	17×20′ + 20×16′ + 4×12′	41	7.2%
14×14 deck	196 ft²	13×20′ + 18×12′	31	6.3%
14×16 deck	224 ft²	22×20′ + 10×12′	32	7.0%
14×20 deck	280 ft²	10×20′ + 10×16′ + 28×12′	48	8.5%
16×16 deck	256 ft²	24×20′ + 13×12′	37	8.0%
16×20 deck	320 ft²	11×20′ + 12×16′ + 31×12′	54	8.5%
16×24 deck	384 ft²	26×20′ + 22×16′ + 6×12′	54	7.2%
20×20 deck	400 ft²	14×20′ + 15×16′ + 40×12′	69	9.1%

5½″ grooved boards, 3/16″ gaps, ¾″ overhang, joists 16″ o.c., 5% spare. Uses the lower-waste of seamless or staggered-seam layouts. Notice how sizes that fit the stock lengths (a deck framed at 15′-9½″ instead of 16 ft) waste far less. Try yours in the board calculator.