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MaterialCalc — 10x12 Deck Material List Calculator

Estimate prepared 09/02/2026. Estimates only; verify against your plans before ordering.

10x12 Deck Material List Calculator

The dimension the joists span.

Under 30 in and no guardrail is required.

%

Result

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10x12 is the smallest deck worth building and the cheapest per square foot, because at 24 inches high it needs no guardrail — and railing is a quarter of the cost of a small deck. 120 square feet, everything in single board lengths, no cutting waste to speak of.

Assumptions used

These are the numbers behind the result. Where one of them is soft, the cost range widens rather than pretending to a precision the data does not have.

Lumber waste allowance
0.1

Cut-offs, crooked stock and the boards you set aside.

Standard industry overage — Industry standard, varies by supplier, checked 09/01/2026

Concrete waste allowance
0.1

Covers spillage, over-excavated holes and forms that bulge. Footings dug by hand run higher than forms.

Standard industry overage — Industry standard, varies by supplier, checked 09/01/2026

Deck board coverage width
5.5 in

A nominal 5/4x6 or 2x6 board covers 5.5 in. Gaps come out of the waste allowance.

Home Depot / Lowe's published product data — Published product data, checked 09/01/2026

Gap between deck boards
0.1875 in

Drainage and expansion. Composite wants a wider gap than wood — check the maker.

Trex and TimberTech installation guides — Industry standard, varies by supplier, checked 09/01/2026

Deck joist spacing
16 in o.c.

Composite decking laid diagonally usually requires 12 in instead.

International Residential Code (2021) — Published product data, checked 09/01/2026

Deck beam post spacing
8 ft

IRC deck provisions (DCA 6) — Industry standard, varies by supplier, checked 09/01/2026

Deck screws per square foot
3.5 screws/ft²

Fastener manufacturer coverage tables — Industry standard, varies by supplier, checked 09/01/2026

Prices verified 09/01/2026 (US national average, big-box retail shelf price and regional ready-mix quotes). Regional adjustment: Blended from RSMeans city cost index bands and BLS construction wage differentials.

The formula

Board rows = 10 ft of width ÷ 5.6875 in per row = 22 rows, each taking one 12 ft board. Joists = (12 ft ÷ 16 in) + 1 = 10, each spanning 10 ft. Two posts carry the 12 ft beam. No railing, because at 24 in the code does not require one.

Worked examples

10x12 at 24 in, pressure-treated

Deck length: 12 Deck width: 10 Height above grade: 24 Decking material: pt Waste: 10

120 ft², about 25 boards and 11 joists on 2 posts. No railing required — the cheapest deck geometry there is.

Same deck at 36 in high

Deck length: 12 Deck width: 10 Height above grade: 36 Decking material: pt Waste: 10

Identical material list, but now guardrails are required. That is 32 ft of railing, often $1,000 or more, for one extra foot of height.

10x12 in composite

Deck length: 12 Deck width: 10 Height above grade: 24 Decking material: composite Waste: 10

Same frame, roughly triple the decking cost. On a deck this small the absolute difference is modest — this is the size where composite is easiest to justify.

Choosing materials

  • Keep it under 30 inches high. Above that the code requires guardrails, and 32 linear feet of railing costs more than the entire frame underneath this deck.
  • 2x8 joists span 10 ft comfortably in any common species, so this is the one deck size where the lumber choice is genuinely free.
  • Everything comes in single lengths — 12 ft boards across 10 ft of width, 10 ft joists across a 12 ft run. No butt joints, no blocking, no waste beyond the odd crooked board.
  • Two posts and two footings. This is a weekend of digging rather than a week, and it is the size where a homeowner can realistically do the whole job.
  • If it attaches to the house it still needs a proper ledger with flashing and lag bolts. Small decks fail at the ledger exactly like big ones do.

Common questions

How many boards for a 10x12 deck?

About 22 rows to cover 10 ft of width, each taking one 12 ft board, so roughly 25 boards with waste. Everything comes in single lengths at this size, which is why there is almost no cutting waste.

What does a 10x12 deck cost?

Materials for a pressure-treated 10x12 at ground level typically run $1,100 to $1,800. In composite, $2,400 to $3,600. Contractor-built, roughly $4,800 to $7,200 pressure-treated.

Do I need a permit for a 10x12 deck?

Often not, if it is freestanding, under 200 square feet and under 30 inches high — many jurisdictions exempt exactly that. Attach it to the house and the exemption usually disappears. Check locally before you dig.

How many footings does a 10x12 deck need?

Two along the outer beam at 8 ft centers if the house side carries a ledger. Freestanding, four — a beam and two posts on each long side.

What size joists for a 10 ft span?

2x8 at 16 in on center works in every common framing species at this span, with margin. There is no reason to go heavier unless you are planning a hot tub.

Can one person build a 10x12 deck?

Mostly, yes. The footings and the beam want a second pair of hands, and the ledger has to be set level, but the framing and decking are within reach of one person over a few weekends.

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