How to take off a column, a footing and a beam in detail

1. Concrete and formwork

Concrete = section × length. Formwork is the area in contact with the concrete: the four faces of a column, the soffit and the two sides of a beam, the sides of a footing. A footing poured against the soil in a trench needs none. Panels are bought once and reused: the number to buy is the area divided by a panel and by the number of uses.

2. Reinforcement by mark

Each mark is a shape, a diameter and a number of bars: longitudinal bars, stirrups (cadres) closed with two hooks, starter bars (attentes) left sticking out of a footing or a column to connect the next element, and the meshes of a footing. The cut length of a stirrup is the perimeter of the core inside the cover plus the two hooks; the weight of a bar is its length times π × Ø² ÷ 4 × 7 850 kg/m³. Offcuts are added by diameter.

Worked example: a 30 × 30 cm column, 3 m high

Four Ø12 bars, Ø8 stirrups every 15 cm, 3 cm cover, hooks of 10 Ø:

• Concrete: 0.30 × 0.30 × 3 = 0.27 m³. Formwork: 4 × 0.30 × 3 = 3.60 m².
• Stirrups: ⌈300 ÷ 15⌉ + 1 = 21, each 2 × (24 + 24) + 2 × 8 = 112 cm.
• A 1.20 × 1.20 m footing, 40 cm thick, with a Ø12 mesh every 15 cm and 5 cm cover: 8 bars each way of 170 cm with their turn-ups, 0.576 m³ of concrete and 1.92 m² of side formwork if formed.

Pours and stripping

The number of concrete trucks is the volume with waste divided by the capacity of a truck. Sides come off before the soffit and the props of a beam; the delays depend on the cement, the weather and the loads, so take them from the specification and the engineer.

What this does not cover

The count does not size the element: sections, diameters, spacings, covers, laps and anchorages come from the engineer’s drawings, and the bar schedule takes precedence.