Working Platform Calculator — Width, Guardrail & Platform Levels

BS EN 12811-1:2003 sets minimum platform widths by class (the width includes up to 30mm of toe board). Standard BS 2482:2009 timber boards are 225mm wide, so to MEET each class minimum you lay: W06 (≥600mm) — 3 boards = 675mm, access and inspection only. W09 (≥900mm) — 4 boards = 900mm, light work and painting. W12 (≥1200mm) — 6 boards = 1350mm, general purpose and bricklaying (5 boards is only 1125mm, which is still W09). W15 (≥1500mm) — 7 boards = 1575mm, general purpose with materials. W18 (≥1800mm) — 8 boards = 1800mm, heavy duty with material storage. Most general working scaffolds use W12.

Under the Work at Height Regulations 2005 (Schedule 2), guardrails are required wherever a person could fall a distance liable to cause personal injury. The protection must include: a top guard-rail at least 950mm above the platform edge, at least one intermediate guard-rail (or equivalent) positioned so that no gap between rails exceeds 470mm, and a toe board sufficient to stop people and materials falling (commonly at least 150mm). On scaffolds these figures are the long-standing default; the 2m figure is a common rule of thumb for when collective edge protection becomes essential, not a threshold below which the regulations stop applying.

Scaffold platform levels (lifts) are normally erected at the standard NASC TG20:21 lift height of 2.0m (this is also the maximum lift height under TG20). Workers then position themselves to work comfortably between waist and shoulder height on each lift, so the practical reach from a lift is roughly the waist-to-shoulder ergonomic zone — a guide, not a code requirement. For example, a 6m high wall would typically be served by lifts at about 2.0m, 4.0m and 6.0m (three levels). Each level needs guardrails and safe access. This calculator defaults to a 2.0m lift; lower the value only to model a tighter ergonomic working zone.

Every working platform must have safe access. For scaffolds, internal ladders through trap doors in the platforms are standard. NASC SG25:20 advises that access points should be no more than 30.0m apart, subject to a suitable risk assessment. Stair towers are recommended (over ladders) for scaffolds used by many workers or for frequent access, as they allow easier evacuation and some manual handling of materials. Ladders should extend about 1m above the platform they serve to give a safe handhold.

Work at height regulations apply from any height where injury could result from a fall. Below 2m, the risk assessment determines what protection is needed. Even at low heights, platforms should have secure edges to prevent trips and falls. Best practice is to provide guardrails on all platforms regardless of height, especially where heavy or awkward materials are handled.