How to count concrete, formwork and steel of tie beams, lintels and parapets

1. Length of each element

A tie beam follows the wall: its length is the total run. A parapet is the length of the roof edge. A lintel is the width of the opening plus the bearing on each side.

2. Concrete and formwork

Concrete is the section times the length, increased by the waste. Formwork covers both faces, plus the soffit when the element has to be formed underneath: a lintel does, a parapet does not.

Worked example: 6 lintels of a 1.20 m opening

Bearing 25 cm each side, section 20 × 20 cm, 4 bars Ø10, 5 % waste:

• Length of one lintel 1.20 + 2 × 0.25 = 1.70 m, so 10.2 m in all.
• Concrete 0.20 × 0.20 × 1.70 × 6 = 0.408 m³, with waste 0.428 m³.
• Formwork 10.2 × (2 × 0.20 + 0.20) = 6.12 m².
• Longitudinal steel: 4 × 1.70 × 6 = 40.8 m of Ø10 at 0.617 kg/m, about 25.16 kg.

Tie beam of 40 m and parapet of 36 m

Tie beam 20 × 20 cm with side forms only; parapet 60 cm high and 10 cm thick:

• Tie beam: 0.20 × 0.20 × 40 = 1.600 m³, formwork 40 × 0.40 = 16.00 m².
• Parapet: 0.10 × 0.60 × 36 = 2.160 m³, formwork 36 × 1.20 = 43.20 m².

What this does not cover

The count does not choose the section, the bars, the stirrups or the lap, and does not check anything structural. It takes them from the engineer’s drawings.