Loads
Platform load per bay from the BS EN 12811-1 load class
- where
- imposed load on one bay (kN)
- uniformly distributed load for the load class (kN/m²)
- bay length (m)
- platform width (m)
- equivalent mass on one bay (kg)
Explain this equation
Turns a BS EN 12811-1 load class into the total load one bay of platform is designed to carry, for loading notices and briefing other trades.
Each load class has a design load per square metre: 0.75, 1.5, 2.0, 3.0, 4.5 and 6.0 kN/m² for classes 1 to 6. Multiplying by the bay's platform area gives the total load in kN. Dividing newtons by 9.81 turns force into an equivalent mass, which is easier to picture. The standard also requires a concentrated load (1.5 kN for classes 1 to 3, 3 kN for 4 to 6) on a small area.
Load equals pressure times area; mass equals force divided by g.
Sense check: class 3 (2 kN/m²) on a 2.4 × 1.25 m bay is 6 kN, about 610 kg: a few people plus light materials. Class 2 is half that.
Watch out: the safe load is per bay, not for the whole lift at once, and depends on the scaffold being built to the matching design.
Turns a BS EN 12811-1 load class into the total load one bay of platform is designed to carry, for loading notices and briefing trades.
Enter your values to see the result.
Good to know
BS EN 12811-1 Table 3 uniformly distributed loads: class 1 0.75, class 2 1.5, class 3 2.0, class 4 3.0, class 5 4.5, class 6 6.0 kN/m². Concentrated load on 500 × 500 mm: 1.5 kN for classes 1–3, 3.0 kN for 4–6. Typical uses: class 2 light access and painting, class 3 general building work, class 4 and above heavy masonry and stacked materials. A loading sign at each access point should state the class and the safe load per bay.
Common mistake
Treating the bay load as one point load you can stack anywhere: the class is a spread load, and a pallet of blocks on one board can exceed the concentrated and partial-area limits.
Limits
Imposed load only for one bay of one lift. Not a check of the scaffold, which also depends on bay length, number of loaded lifts and ties (TG20 compliance sheet). For planning and estimating only. This does not replace TG20:21 compliance (a TG20 compliance sheet or eGuide output) or a scaffold design by a competent person.
Sources
- BS EN 12811-1:2003 Temporary works equipment. Scaffolds. Performance requirements and general design (Table 3 load classes; 5.5 side protection; Annex A cladding force coefficients)
- Health and Safety Authority (Ireland), Code of Practice for Access and Working Scaffolds (sole boards ≥ 1000 cm², ties ≥ 6.1 kN, façade bracing at least every six bays, tower height to least base ≤ 3, toe-boards ≥ 150 mm)
- NASC TG20:21 Good practice guidance for tube and fitting scaffolding (Operational Guide, Design Guide, User Guide and eGuide compliance sheets)
Results are calculations from the published methods and figures shown, and depend on the data you enter. For planning and checking only. Scaffolds must be erected to NASC TG20 or a bespoke design by competent persons, and lifting operations planned under LOLER by a competent person. Never rely on these results instead of a design, a lift plan or manufacturer ratings.