Temporary Works Design Calculator

Design scaffolding, formwork, and shoring per BS 5975, OSHA 1926, and AS 3610. Calculate loads, wind forces, concrete pressures, member capacities, and tie forces.

BS 5975 · OSHA 1926 · AS 3610

Design Parameters

Scaffolding Parameters

Design Results

PASS
Imposed Load
2.00 kN/m²
Dead Load
2.50 kN/m²
Total Load
4.50 kN/m²
Wind Load
0.049 kN/m²
Member Force
5.85 kN
Member Capacity
20.0 kN
Tie Force
0.20 kN
Tie Spacing
4.0 m

Utilization

Standard Leg29.3%

Notes

  • Duty class: General Purpose (2 kN/m2)
  • Wind speed: 20 m/s, Cf = 0.2
  • Wind pressure: 0.049 kN/m2

About Temporary Works Design Calculator

The temporary works design calculator assesses scaffolding, formwork, and shoring loads against member and prop capacities per BS 5975, OSHA 1926, and AS 3610. It is used by temporary works designers and site engineers to verify standard leg loads, tie forces, formwork concrete pressure, and prop utilisation before erection.

Pick the works type and design standard, then enter the geometry, duty class or pour parameters, and wind speed. The tool returns the dead, imposed, and total loads, the governing member force and capacity, the formwork concrete pressure and ply span, and the utilisation ratio with a pass or fail result, all in real time.

How It Works

  1. For scaffolding, sum the dead load (0.5 kN/m2 per lift) and the duty-class imposed load, then find the standard leg force from the bay area.
  2. Compute the wind pressure q = 0.613*V^2*Cf/1000 and the resulting tie force over the bay, using Cf = 1.3 sheeted or 0.2 open.
  3. For formwork, take the lesser of the hydrostatic pressure and the CIRIA R108 limit, then check the plywood span and the span/270 deflection limit.
  4. For shoring, multiply the load per area by the prop spacing squared, apply the multi-floor redistribution factor, and compare with the prop capacity for the utilisation ratio.

Worked Example

A general-duty scaffold (imposed 2.0 kN/m2), 10 m high in 5 lifts, with a 2.0 m x 1.3 m bay. The dead load is 0.5*5 = 2.5 kN/m2, so the total load is 2.5 + 2.0 = 4.5 kN/m2. The standard leg force is total*bay_area/2 = 4.5*(2.0*1.3)/2 = 5.85 kN. Against a 20 kN tube capacity the utilisation is 5.85/20 = 0.29 (29%), which passes.

Formulas

Wind pressure
q = 0.613 * V^2 * Cf / 1000
Scaffold standard leg force
F = total_load * bay_area / 2
Formwork concrete pressure (CIRIA R108)
P = min(gamma*h, gamma*(1 + 1.5*sqrt(R))*sqrt(17.5/(T + 17.5)))
Member utilisation
utilisation = load / capacity

Standards & References

  • BS 5975
  • EN 12811
  • CIRIA R108
  • OSHA 1926
  • AS 3610

Frequently Asked Questions

Which temporary works can the calculator handle?

It covers three types: access scaffolding (duty loads, standard leg forces, wind, and tie forces), formwork (concrete pressure, plywood span, and deflection), and shoring (prop loads with multi-floor redistribution), each checked against BS 5975, OSHA 1926, or AS 3610.

How is formwork concrete pressure calculated?

It takes the lesser of the full hydrostatic pressure gamma*h and the CIRIA R108 design limit, which depends on the pour rate R and the concrete temperature T. A faster pour or colder concrete gives a higher design pressure on the form face.

What is the deflection limit for formwork?

The tool applies the BS 5975 surface deflection limit of span/270 for the plywood sheathing, alongside a maximum allowable span derived from the concrete pressure, so the form face stays within tolerance.

How is the pass or fail result determined?

The governing member or prop force is divided by its capacity to give a utilisation ratio. A ratio of 1.0 or less passes; above 1.0 fails. Scaffold tubes are checked against a 20 kN capacity and props against their rated light, medium, or heavy capacities.