Curved framing

The continuous line of curved stairs is more enticing than the interruptions caused by newels. Timber framing in the form of laminated strings assisted by a wrought-iron flitch plate date back to the eighteenth century (see Figure 6.1c), though carpenters often propped their work with a slender iron column as extra security. Otto Salvisberg at Roche Chemicals, Welwyn Garden City,

Figure 6.3 Typical page from manufacturer's catalogue (by kind permission of Richard Burbidge & Son Ltd)
Figure 6.4a Historic examples: Stairs in Queen Anne's Gate, London, 1704, from Cruikshank, D. and Burton, N., Life in the Georgian City, Viking, 1990

put in a chromium-plated tube to camouflage his belt and braces attitude to curved strings rising 3800 mm (Figure 6.5a).

The construction resembles the open tread stair except that the strings are made from glued ply or blocks (like laminboard) with face veneers and lip-pings. The integral strength comes from the tread acting with the inner and outer strings (Figure 6.5 b). An alternative strategy is to use a central post, either solid or laminated, as a drum to carry the tapered end to each tread (Figure 6.5c). A more elegant solution found in Central Europe is to carve a curved newel into a hollow half cylinder. This shape fulfils the role of a newel in supporting treads,

Figure 6.4b Historic examples: Replacement stair, Morton House, Highgate, London, 1990 (Julian Harrap)

Figure 6.4c Historic examples: Hatfield House Stairs, 1620

ope walls behind a dog-leg stair whilst the boxed newel is set up for framing the winders; the remaining straight flights can be assembled from open treads or cased in with tread and riser as required.

Wooden treads can be suspended from the trimming timbers of the floor above (refer forward to Figure 7.6 b). Here the suspenders support the string, but this can also be adapted to support individual treads on short battens, as designed by Walter Segal for self-build clients (Figure 6.6b). If hangers are placed at the edge of nosings, an intermediate baluster has to be provided to reduce the space between balusters to the maximum of 100 mm.

Figure 6.4b Historic examples: Replacement stair, Morton House, Highgate, London, 1990 (Julian Harrap)

as well as the inner strings and handrail (Figure 6.5d), without destroying the line of the balustrade. (Compare with Figure 6.5e for a traditional solution.) Carpenters' manuals from the eighteenth and nineteenth century are worth studying. Figure 6.5/ reveals the geometry of oval stairs similar to the elegance in Figure 6.1c.

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