Guarding is required to safely protect the edges of a floor, gallery, roof, rooflight or any other area to where people have access such as car parks. Guarding should be designed in accordance with the requirements of Approved Document K, ‘Protection from falling, collision and impact’ and BS 6180:1999 (see note in footer) ‘Barriers in and about buildings. Code of practice’. The glazing must also comply with the requirements of Approved Document N, ‘Glazing – safety in relation to impact, opening and cleaning’
Guarding should be at an appropriate height and configuration and capable of resisting the expected horizontal design loads. Guidance on the design loads are contained in Table 4, BS 6399: Part 1, 1996 and are described as;
1. Horizontally uniformly distributed line load (Kn/m)
2. Uniformly distributed load applied to the infill (Kn/m2)
3. Point load applied to part of the infill (Kn)
The design loads to be applied depend on occupancy characteristics. Two examples of differing conditions are provided in the table below
The guidance provided within BS 6180:1999 on the design of glass barriers and infill panels in and about buildings describes three types;
1. A full height barrier where the glass forms part or whole of a wall.
2. A barrier with a glass infill panel where the main frame of the barrier consists of a top rail and baluster. The frame is required to resist the horizontal loads described above. The glass infill panel does not provide any support to the main frame and has to resist the horizontal loads also described above.
3. A free standing glass protective barrier where the glass should be designed to withstand the horizontal design loads. Each glass plate is clamped to the structure along its bottom edge and a handrail is attached to the top edge of the glass. There are no balusters
The guidance is quite explicit in so far as a handrail must be attached to the top edge of the glass.
Many designers consider that this requirement is a constraint that is not acceptable and look for a solution that does not require a handrail at all or, a handrail that is not attached to the top edge of the glass. This approach creates a compliance issue.
In exceptional circumstances it may be acceptable to some building control bodies to accept a variation to the guidance. The variation will need to be justified and the justification may include the following:
A statement concerning the reason for the variation to the guidance and interpretation of Part K & BS 6180: 1999.
• Occupancy characteristics (including numbers, activity, age and profile etc)
• Building usage or purpose group.
• Prevailing conditions such as occupancy, layout, barrier configuration, glazing area.
• Risks associated with sudden impact, fracture and fire.
• Additional safety measures.
• Height of fall.
• Manifestation and degree of transparency.
• Provision of secondary barriers such as fixed seating.
• Traffic factors such as traffic dynamics and traffic flow.
• Safety factors.
• Structural design including calculations and drawings.
• Manufacturer’s details and supporting design.
• Agrément or other acceptable certification.
• Glazing material properties and characteristics.
• Psychological factors.
• Access.
• Maintenance regime and longevity of fixings.
• Vandalism.
• The safe design of the top edge
The above design criteria is not exhaustive but should be included in a risk assessment and submitted to the building control body as a justification statement for the variation to the design guidance provided by the Approved Documents.
I would welcome any further comments especially from structural engineers or manufacturers.
note; BS 6180: 1995 Code of Practice for protective barriers in an about building, cited in the Building Regulations have been superseded by BS 6399: Part 1, 1999. Barriers in and about buildings. Code of practice
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