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Concrete Wall Calculator

A poured wall is a tall, thin pour, which makes it unforgiving. Get the volume wrong and you are left with a cold joint running horizontally through the wall at exactly the height the concrete ran out. Enter length, height and thickness below.

Wall lengthHeightThickness
Concrete wall: length, height and thickness
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The formula

Volume = Length × Height × Thickness

Worked example. A retaining wall 6 m long, 1.2 m high and 200 mm thick: 6 × 1.2 × 0.2 = 1.44 m³. With 5% waste that is 1.51 m³, roughly 3.6 tonnes. Footings underneath are a separate pour — size them with the footing calculator and order both together.

Useful shorthand: a wall 1 m high and 200 mm thick swallows 0.2 m³ per linear metre. In imperial, a 1 ft high × 8 in thick wall takes 0.67 ft³ per linear foot.

Typical wall thicknesses

Wall type Thickness
Low garden retaining wall 150–200 mm (6–8 in)
Basement or foundation wall 200–300 mm (8–12 in)
Structural shear wall Engineer’s design
ICF wall core 150–200 mm (6–8 in)

Any retaining wall over about a metre, and anything structural, needs designing properly. The load is not just soil weight — it is soil weight plus whatever water is trapped behind it.

Pouring a wall without ruining it

  • Pour in lifts of about 500 mm, working around the wall rather than filling one end first. Vibrate or rod each lift to drive out trapped air, and keep going — do not stop for lunch halfway up.
  • Brace the formwork harder than feels necessary. Wet concrete exerts real hydraulic pressure, and a blowout at 1.5 m is a very bad afternoon.
  • Drain retaining walls. Weep holes at the base, free-draining gravel behind, and a perforated pipe to somewhere useful. Most retaining wall failures are water pressure failures, not concrete failures.

Frequently asked questions

How much concrete is in a wall per metre?

A wall 1 m high and 200 mm thick contains 0.2 m³ per linear metre. Scale it directly: double the thickness and you double the volume.

What grade for a retaining wall?

C25 to C30 for garden walls, C30 to C35 with reinforcement for engineered walls. Air-entrained if the wall faces freeze-thaw cycles.

When can I strip the formwork?

Vertical side shutters after 24 to 48 hours in warm weather, longer when it is cold. Anything propping a suspended element stays much longer. Design strength arrives at 28 days.

Should a poured wall be reinforced?

Retaining and structural walls, yes — vertical bars tied into the footing plus horizontal bars, to design. A low freestanding garden wall on a good footing may not need it.

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