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How Much Concrete for 150 Feet of Footing?

For 150 linear feet of a 16 by 8 inch footing, plan on about 4.94 cubic yards. How much concrete for 150 feet of footing at other sizes is in the table; trench footings poured against the soil often use more than the math because trench walls are never perfectly straight.

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Footing math

  1. Cross-section: 16 in × 8 in = 1.333 ft × 0.667 ft = 0.889 sq ft.
  2. Volume: 0.889 × 150 ft = 133.3 cu ft.
  3. Yards: ÷ 27 = 4.94 yd³.

Yards for common footing sizes over 150 feet

Footing (width × depth)Cubic feetCubic yardsYards +10%
12 × 6 in75.02.783.06
16 × 8 in133.34.945.43
20 × 8 in166.76.176.79
24 × 10 in250.09.2610.19
24 × 12 in300.011.1112.22

Sizing and depth

Footing size comes from the load, the soil and local code. A frequently used rule of thumb is a footing about twice as wide as the wall it supports and at least as deep as the wall is thick, but your building department sets the real minimum. The bottom must sit below the local frost line. See footing depth and the frost line.

Trench pours run over

Earth-formed trenches eat extra concrete. Over-digging by an inch on each side of a 16-inch footing adds about 12 percent. Measure the trench after digging and size the order from those numbers.

Rebar and inspection

Footing steel is usually two or more horizontal bars held up off the soil. Book the inspection first, then the concrete: a failed inspection with a truck on the way is an expensive afternoon.

Questions people ask

How many yards for 150 feet of 16x8 footing?

About 4.94 cubic yards before waste.

How many yards for 150 feet of 24x12 footing?

About 11.11 cubic yards.

How much extra should I order for a trench footing?

About 10 to 15 percent, since trench walls are rarely straight.

How deep should a footing be?

Below the local frost line and on undisturbed soil; your building department sets the minimum.

How thick should the base under the slab be?

About 4 inches of compacted gravel is common for residential slabs, more on soft or poorly drained soil.

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