061026.Bradford, Lansdown Hill, Looking Up Beckford's Tower

October 26, 2006 at 1:09 AM | Posted in Architecture, Bath, Bradford, somerset, stairs, Towers | 5 Comments

Popularly called “cantilevered stairs,” these are in fact “hanging stairs (?)” since the heavy stone treads are not set into the wall deep enough to provide an adequate cantilever. Although I could be off on these particular stairs since they are set in a square tower (see thumbnail sectional), structurally, no one quite knows why “hanging stairs” remain standing. They were popular from the Georgian on to the Victorian Period (mid 18th C-mid to late 19th C). Medieval variations exist in turrets that were not cantilevered or hanging, but all connected to a central spine, which took their weight. Here, each step would break under its own weight, if not supported by the step below it! Load testing reveals these are stronger stairs than many contemporary decorative structures, functioning like a spring against the foundation. However, the one flaw in placing the fate of an entire spiral of stairs on each “step vertebra” is that if one fails, the entire staircase collapses. Typically, fires quickly cause catastrophic failure (and progressive collapse) to these structures after a single step overheats and cracks, making the beautiful form obsolete and dangerous without modern material safeguards.

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