/Spiral stairs to BS 5395 P42 'are a possibility for means of escape
3.25d and e fire resistance and guarding is needed for flat roof escape routes
Escape over flat roofs - second escape only and then not for institutional buildings or for the public (and must be over a roof of the same building) 3.25
If stair goes on down it should be clear that the final exit is at this level 5.31
Basements in a single stair building this basement should have a separate stair. In a two-stair building one stair may go to protected and ventilated lobby or corridor at basement level 248-242
Combined plan and section
Figure 34a Core limitations for commercial buildings: Limitations imposed by National Building Regulations
Figure 3 4b Typical specified travel distances to stairways in a hotel building given by international planning guides
accommodation stairs are the next most-used element, whilst the wings contain the four new escape routes and ancillary lifts. In case of fire, the fire brigade teams would tackle the problem from the wings where allocated lifts and dry risers are sited either side of the open plan area. The layout combining new and old elements on the Financial Times site has pro duced a new concept of conservation and one that shows the most interesting combination of technology in arranging lifts and stairs today.
The other reconstruction indicating changes in attitude to fire safety is the story of the Economist Building in relation to the original core plan (circa 1964) and the remodelling undertaken in 1992.
Figure 35a Core arrangements for offices: Single zone layout: main stair and lifts at junction of two wings, with secondary stairs at ends of corridors
Figure 3 5d Double zone layout using H or U form, typical pattern to devise window walls to all sides of offices. Variations include V, X and Y forms around core zones
Figure 3 6a Multiple bay plans: Triple zone layout with parallel corridors and central core (Phonix-Rheinrohr AG Germany Competition 1955)
Figure 3 5c Double zone layout with central core: typical single staircase design for low-rise could however form a pattern for development with equal sized cores spaced at intervals in length of block
Figure 3 6c Staggered triple zone layout (Phonix-Rheinrohr AG Germany 1957, scheme completed). Architects: Helmut Hentrich and Hubert Petschnigg
The building, like Bracken House, falls under the Section 20 legislation that applies to 'over cube' premises in Inner London; for definition refer to Chapter 10.
The initial designs had to comply with the former requirements of the London Fire Brigade to have facilities to climb directly onto escape stairs in case of lift failure. Such demands, with internally sites stairs, meant two open-air shafts within the core. Each shaft had a rung ladder accessible to windows on both escape route landings (Figure 3.9a). It was a solution favoured in old Parisian apartment blocks. The changes brought about by 'positive' air pressure devices for stair and lobbies have revolutionized the layout of inner cores. At the Economist Building it enabled service areas to be enlarged to contain a kitchen as well as male and female lavatories at every floor as opposed to alternate levels (Figure 3.9 b).
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