Metal balustrading

The choice of bronze or steel for balus-trading is dictated by the engineering. Problems with the proven strength of bronze imply that bronze, like aluminium, is often utilized as a sacrificial surface over steel cores in structuring balustrades. The constructional restraints are governed in the UK by Codes of Practice2 and are concerned with lateral strength and fixings. This is a separate issue to that raised by the Jiricna-Wells suspended stairs where the total ensemble of balustrading and stair framing have to be assessed as structural engineering.

The traditional concept can be compared to a framework infill, comprising the following elements and illustrated in Figures 7.8a-g.

• Vertical members, termed standards, provide the main support.

• Rails, termed handrails and core rails, the latter making a sub-frame (if needed) for the infilling members.

• Balustrades, formed with bars, mesh or sheet materials.

• Connections, welding, set screws, sleeves and cleated brackets.

The assembled framework is connected together in panels by set screws and on-site welding. The supporting strings can be timber, steel (plate or tubular) or reinforced concrete (either in situ or pre-cast) (Figure 7.8g).

The geometry of the assembly is critical to the overall stability: long runs to landings and straight flights will need heavier standards or stays. Shorter flights with dog-leg or triple-turn layouts provide sufficient return lengths to stiffen the framing. Circular balustrading is also stiffer than straight runs.

Base fixings are another factor; direct vertical fixings have less torque than side-mounted standards. The advantage of the former stems from the face-to-face bolting that can be obtained from base plates to the stair or landing structure, with loading in line with the standards. The actual connections vary with the stairs: refer to Figure 7.8 for a range of alternative details.

Side fixings into the edge of treads or landings save space since Building Codes in the UK and the USA permit the required stair width to be measured to the edge of the handrail. The actual girth of tread is therefore minimal as compared with base-mounted balustrades which can add 75 mm to the width of stair or landing construction at balustrade locations. Side fixings do not necessarily save space since the well size has to be sufficient to accommodate the 'L'-shaped standards apart from adequate dimensions if wreathings are employed. Balustrades set clear of tread and landing surfaces have the crucial advantage that floor coverings are not perforated which makes maintenance and replacement an easier proposition.

Angle to suit \ requirements

Angle to suit \ requirements

N50-16 ANGLE BEND

END PLUG

N50-17

SPLIT CONNECTING SLEEVE

N50-17

SPLIT CONNECTING SLEEVE

N50-18

CHAIN EYE PLUG

END PLUG

WALL RAIL BRACKET

N50-16

-N50-13 or

N50-14 or N50-12 N50-15

N50-21 SADDLE CROSS

N50-22

ANGLED SADDLE JOINT

N50-16 or N50-22 N50-3 or N50-24

N50-22

ANGLED SADDLE JOINT

N50-16

-N50-13 or

N50-14 or N50-12 N50-15

Figure 7.8a Traditional metal balustrading: Industrial balustrading (by kind permission of Norton Engineering Alloys Co. Ltd)

A compromise solution is to devise a string component for both treads and landings which contains vertical fixings for the balustrading and horizontal connections to the surrounding structure. Traditional detailing involves hardwood sections (Figure 7.8g) but tubular steel sections or pre-cast concrete will serve equally well; the latter has the advantage that factory finishes such as terrazzo or tile can be applied to give a high quality setting for the balustrade. The arrangement also means that the minimal structural width can be provided for treads, etc., whilst the handrail/standard/string component occupies a zone within the well. Straight string features that project above nosing lines to stairs and landings also facilitate maintenance whereby cleaning operations do not spill dirt down into the staircase well.

The 'guarding' rules for balustrades to stairs and landings under the National Building Regulations are explained in Section 10.2 with illustrations in Figure 10.2. The worst situation occurs where multi-occupancy is planned and the designer is faced with a variety of conflicting advice under the Regulations as to the ideal height for the handrail. Aalto resolved this dilemma by running handrails in duplicate, one for the adults and one for the children.

Another sensible solution is to choose a standard height for the principal balustrade element, be it railings or walling, and then mount the handrail separately to follow the mandate of the Regulations.

Figure 7.8b Traditional metal balustrading: Balustrade panels

Figure 7.8c Glass & sheet panels, designed by Foster and Partners

Figure 7.8e Traditional metal balustrading: Horizontal rail (by kind permission of Aidrail Ltd)

In this method the geometry of the spandrel treatment (perforate or solid) can at least match the stair geometry.

Aluminum or galvanized steel industrial guard railing is another 'off-the-peg' balustrading that is effective in certain categories of work — safety barriers for maintenance stairs and accessways, even external works. The Meccano-like components comprise universal sockets and tubes held together by inset screws. The appearance with 'arthritic' joints may not be to everyone's taste; mesh panels will need to be fitted where children are at risk.

A non-traditional concept is to place the balustrade assembly as a vertical infilling to a minimal stairwell. The panels are supported by newel posts and the handrailing bracketed to provide a continuous hand-

Figure 7.8d Traditional metal balustrading: Mesh panels (by kind permission of Aidrail Ltd)

Figure 7.8c Glass & sheet panels, designed by Foster and Partners

Figure 7.8f Traditional metal balustrading: Connections (welding, set screws, sleeves & cleated brackets)
Figure 7.8g Traditional metal balustrading: String to balustrade details (timber, steel, concrete)

hold as Figure 8.5/ Stretched cable balus- The rhythmic variation of metal balusters trades are another novel adaptation of is perhaps the most memorable image marine detailing borrowed for buildings. (variations are given in Figures 1.9a-d).

Figure 7-9b Unusual construction: Brass frame, with handrail, enamelled standards, wires as infill and capping to string, Aarhus City Hall, 1943, Architect: Arne Jacobsen

Figure 7.9a Unusual construction: Wrought iron loops, John Soane Museum, London, 1790

Figure 7-9b Unusual construction: Brass frame, with handrail, enamelled standards, wires as infill and capping to string, Aarhus City Hall, 1943, Architect: Arne Jacobsen

Figure 7.9c Unusual construction: Trussed balustrade with steel handrail, verticals and folded steel treads, Havas Conseil, Paris, 1960s

Figure 7.9d Rhythmic decoration at Kedleston Stairs, 1790s, Architect: Robert Adam

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