On 3rd January 1859 at about 10:45 pm a stone staircase at the Royal Polytechnic Institution on Regent Street (now The University of Westminster) collapsed, killing a child and seriously injuring many others. The following day “The Standard” reported how the flight had been filled with people leaving the building after visiting an exhibition. The flight collapsed onto another flight below, which led to people falling 30′ into the basement below.
Apparently the staircase had stood without any problem since being built 20 years earlier. The article goes on to say,
“Nevertheless it must be mentioned, the staircases, which have two spiral flights from a centre, having been worn away by the continued traffic of years, had been recently cased over with an iron lattice-work on the surface from top to bottom, with the supposed object of strengthening them; and there cannot be much doubt, from an inspection of the material, that the mason, in interweaving this iron lattice work all over the steps (which gives them the appearance of a tessellated pavement), have inconsiderately cut too deep into the stone, in order to fix in the iron and incorporate it with the steps, and that it is this excessive incision which is intended to have a stiffening and strengthening effect, but which the sad result proves had only a destructive and debilitating one.”
“The Builder” January 22nd 1859 carried an article describing the coroners inquest. There were conflicting reports about which part of the staircase collapsed first, but there is also some more information about the condition of the flights:
“The landing was cut to a feather edge, and nearly on the point of this edge rested the first of a flight of eighteen steps each 5 feet long.”
“One of the steps near the (lower) landing had been broken and mended with cramps.” and
“A large portion of the surfaces of both landings was cut out to make a key for cement, to fill up the cavities that had been worn away, and there was settlement in the wall…”
Apparently the treads broke about 5″ away from the wall along the joint where the iron trellis had been inserted into them.
In the bottom landing there was also a “flaw or defect visible in the stone itself where it had broken” The landings were 4 1/2 ” thick, however where the first tread sat on to the lower landing the landing stone had been reduced to as little as 3/4″ in places.
The architect appointed by the coroner reported how he conducted various experiments :
“The experiments I have tried show that a step, with a piece of stone let into the top on the usual plan would have broken with the same weight upon it as broke a step with the trellis let in. If the steps had not been cut at that particular place they would have broken off close to the wall instead of 5 inches from it. The effect of the cutting would be to accelerate the fall after the landing had broken. The experiments prove that the steps, as altered would have borne a weight equal to four times what they were required to carry, provided the bottom remained firm.”
On June 20th 1859 The Daily News carried another story about the the legal actions that had been brought against the Polytechnic following the accident. There seem to have been two theories formed about why the flight had collapsed, the first:
“…instead of replacing the worn stones with new ones, they cut away the worn portions of each and let in pieces of iron, thus weakening their strength, and lessening the security of the whole staircase.”
and the second:
“…a natural flaw in one of the cracked stones of the landing, which would not have been discovered from external examination, and experiments had since proved that the staircase must have given way from that cause. The alterations in the steps had… nothing to do with the cause of the accident.”
In the end the Chief Baron went with the second theory, although I suspect that the collapse was probably caused by a combination of the two.
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