Guide to Conversion of Traditional Buildings

4.4 Pedestrian protective barriers

Mandatory Standard

Standard 4.4

Every building must be designed and constructed in such a way that every sudden change of level that is accessible in, or around, the building is guarded by the provision of pedestrian protective barriers.

Limitation:

This standard does not apply where the provision of pedestrian protective barriers would obstruct the use of areas so guarded.

4.4.1 Application of standard to conversions

In the case of conversions, as specified in regulation 4, the building as converted shall meet the requirements of the standard in so far as is reasonably practicable, and in no case be worse than before the conversion (regulation 12 schedule 6).

4.4.2 Commentary

This standard covers the provision of walls or balustrades (barriers) at the edges of sudden changes of level. The guidance specifies where they are required, their height and their design to ensure their strength against defined lateral forces and minimise the risk of people falling or slipping through gaps in the barrier. This is particularly important in buildings where children are, or may be, present.

Many historic buildings incorporate partially guarded changes of level, which are a key part of their character as a traditional or culturally significant structure. Also, many of these buildings are groupings of separate structures, brought together over decades or centuries to form the ‘building’ we know today. In many cases, the separate buildings were on different levels and joining them together has resulted in sudden changes in level at the interface. In domestic and commercial buildings, balustrades of some sort or other protected users against most of these sudden changes in level, but these may not comply with the full requirements of the standard.

4.4.3 Issues to be considered

Typical risks in the conversion of historic/traditional buildings

1. Partially unguarded changes of level in existing buildings.

• The replacement or alteration of the existing balustrade or barrier to comply fully with this standard may be unacceptable spatially, historically or aesthetically.

• Existing balustrades may not meet requirements of the standard in terms of height or resistance to lateral forces or in the openings between features (the ‘100mm sphere rule’).

2. Unguarded changes of level in existing buildings

• Historic industrial buildings often incorporate sudden and unguarded changes of level due to the industrial process they were designed for, or the requirement for the easy movement of goods. These are often less sensitive as historic environments, and suitable new barriers can usually be incorporated to comply with this standard when the buildings are converted to new purposes.

3. Window sills below 800mm with adjacent internal floor levels 600mm or more above external ground level

• Historic windows often have lower sills than specified in this standard but barriers cannot be installed internally, owing to the nature of historic window joinery (shutters, reveal panelling) or window cleaning mechanisms. Externally fixed barriers are likely to affect the design of elevation and/ or streetscape (see also 4.8 guarding of windows).

4. Introduction of ramps to provide accessible routes about the building to satisfy Standard 4.1

• The introduction of ramps within a historic building often means that there is a change in level between the edge of the ramp and the surrounding floor or ground and, where this exceeds 600mm, a balustrade or barrier is required. Barriers of this type may be visually intrusive to the interior of a culturally significant building.

4.4.4 Recommendations to meet the standard

Whether an existing balustrade or barrier can be adapted (either by redesign or the addition of new elements) to comply fully with this standard will depend on the status and importance of the historic building and its sensitivity to change.

a) Design of balustrades/barriers

Existing balustrades can be made safer, particularly for young children, by inserting additional balusters between existing widely spaced balusters, or by adding continuous glazing or metal mesh. It is better to design additional balusters in a simple, obviously modern style rather than to try to replicate the historic fabric. For example, small section, plain timber or metal bars can be painted a dark colour and almost merge inconspicuously with the other components of the balustrade.

Existing non-compliant balustrades can be made safer for children by the application of steel or non-ferrous mesh to one side, or laminated glass panels of sufficient strength, but this must be carefully chosen and designed to accurately fit the opening or to fit between framing members.

b) Height of balustrades/barriers

Existing balustrades can be raised in height by the addition of secondary raised handrails of a similar design to the original or (where appropriate) of an overtly modern design that does not pretend to be part of the original. Fixed glazed panels can also be used.

Balustrades with horizontal members (or other potential footholds) are tempting and easy for young children to climb. If a balustrade in a historic building is a significant part of its interest and must be retained, it can be made safer by the addition of fine grid metal mesh or glass sheeting (laminated) applied to the user’s side.

c) Window barriers

Dependent on the design of a window and the historic value of the glazing, it may be possible to consider the lower section of the window as the barrier if the lateral force requirements can be proven to be met, for example by the use of stronger glazing types, different fixings etc.

Carefully designed minimalist metal (or framed glass) railings can often be fitted across window openings within the depth of the window frame or sash bar. However, this can affect window cleaning mechanisms which rely on the sashes being able to swing inwards and may block escape (see Section 2: Fire). Care should be taken to align the top of a railing with an astragal or meeting rail to minimize visual impact. Darker frames will generally be less visually intrusive to exterior views of the building,

d) Ramp balustrades

Any new ramp should have a sufficiently high upstand to the edge of the raised area that will stop a buggy or a person in a wheelchair running over and off the edge. The need for full height barriers or balustrades to the edges along the length of new external ramps can often be avoided by adjusting the surrounding groundscape to reduce the difference in height and thereby meet the maximum height standard. Alternatively, an external ramp may be provided with a landscaped margin, level with the edge of the ramp for 600mm before grading starts.