Scaffold Load Class Calculator — Class 1-6 Selection

Bricklaying is treated as Load Class 3 (general purpose) under NASC TG20:21, which allows a 2.0 kN/m² uniformly distributed load. This accommodates bricklayers, a mortar tub, and a reasonable stock of bricks. TG20 calls for a clear working width of at least 800mm — typically a 5-board main platform (about 1125mm) so there is room for materials and a working area. Note BS EN 12811-1 Table 3 also requires the platform to support the concentrated loads F1 (1.5 kN over 500×500mm) and F2 (1.0 kN over 200×200mm) on top of the UDL check. If you are storing large quantities of bricks, Class 4 (3.0 kN/m²) may be needed.

BS EN 12811-1 Table 3 defines six load classes by uniformly distributed load (q1): Class 1 (0.75 kN/m²) — inspection only. Class 2 (1.5 kN/m²) — painting, light work. Class 3 (2.0 kN/m²) — bricklaying, rendering. Class 4 (3.0 kN/m²) — blockwork, heavy cladding. Class 5 (4.5 kN/m²) — stone masonry. Class 6 (6.0 kN/m²) — special heavy duty. Each class must also carry a concentrated load F1 (1.5 kN for classes 1–3, 3.0 kN for classes 4–6, over 500×500mm) and F2 (1.0 kN over 200×200mm, all classes). Classes 4, 5 and 6 must additionally carry a partial-area load q2 of 5.0, 7.5 and 10.0 kN/m². Most domestic scaffolding is Class 2 or 3.

Transoms are the horizontal tubes that support the boards, and their maximum spacing is set by the scaffold board's allowable span — not by the load class. Under BS 2482:2009 a 38mm timber board may span up to 1.2m if visually graded or 1.5m if machine graded, and a 63mm board up to 2.5m. Transoms are positioned no further apart than this so the boards do not over-deflect. (BS EN 12811-1 contains no transom-spacing table tied to load class.)

TG20:21 platform widths run from 3 to 5 boards for the main platform, plus up to 3 inside boards. As a guide: 3 boards (about 675mm) for inspection and access only; 4 boards for light duty; and for bricklaying / general purpose work TG20 needs a clear working width of at least 800mm, usually a 5-board platform (about 1125mm) so there is room for a mortar tub and working area. For stone masonry or heavy work, 5+ boards with additional boards for material storage. Inside-board loading must not exceed 0.75 kN/m².

Yes, but within the load class limits. Materials should be evenly distributed, not concentrated in one spot, and the total imposed load (workers plus materials) must not exceed the class q1 limit. Just as important, the platform must also be able to take BS EN 12811-1's concentrated loads — so heavy point items should be placed over a transom where the load path is strongest, and brick stacks kept low and spread out rather than piled in one place. For Class 4–6 work the partial-area load q2 (where a heavy load is concentrated over part of the bay) often governs, so heavy or point-loaded scaffolds should be designed to TG20:21 or BS EN 12811-1 rather than relying on a UDL check alone.