Roof Edge Protection Calculator — Perimeter Guard Rail Quantities

Under the Work at Height Regulations 2005 there is no 2-metre (or any) minimum height — the old '2 metre rule' was abolished. Suitable measures are required wherever a person could fall a distance liable to cause personal injury, so a low parapet or single-storey roof can still need edge protection. It applies to work on flat roofs, pitched roofs near eaves, and new-build or re-roofing work, and must be in place before anyone goes onto the roof. The Regulations require collective protection (guardrails) to be considered before personal protection (harnesses).

BS EN 13374:2025 (the current product standard, which supersedes BS EN 13374:2013+A1:2018) specifies: principal (top) guardrail at least 1000mm above the working surface, measured perpendicular to it; an intermediate guardrail so no gap exceeds 470mm; and a toe board at least 150mm high at the base to stop materials rolling off. The guardrail must withstand the standard's specified loads. (The Work at Height Regulations 2005 set a separate statutory minimum of 950mm for the top guardrail — proprietary BS EN 13374 systems exceed this at 1000mm.)

Free-standing systems use weighted bases (counterweights) instead of being fixed to the building structure. Advantages: no penetration of the roof membrane, quick to install and move, no structural fixings needed. Disadvantages: counterweights are heavy (20-30kg each), the system takes up space on the roof, and some configurations require engineering checks.

Standard post spacing is 2.0m maximum for most proprietary systems. Some heavy-duty systems allow 2.5-3.0m spacing. The spacing must ensure the guardrail can resist the required lateral loads (0.3 kN point load at the top rail) without excessive deflection. For DIY tube and fitting edge protection, 2.0m is the standard spacing.

Mesh infill (or brick guards) is driven by the dropped-object risk, not by the system class. It is needed when small materials could fall through the gap between the top rail and toe board — for example during bricklaying, roofing, or any work where loose materials are present on the platform. The BS EN 13374 classes (A for flat / low-pitch roofs up to 10°, B up to 30°, and C nets up to 60°) grade systems by roof pitch and load type, not by whether mesh is fitted, and Class A guardrail systems are commonly supplied with mesh infill. Decide mesh need from the risk assessment.