Cantilevered staircase

Cantilevered Steps

I was asked to help install a cantilevered York stone staircase at a mews in Kensington, West London to help out a friend.

A cantilever, according to Wikipedia (which is never wrong…) is:

” a rigid structural element, such as a beam or a plate, anchored at only one end to a (usually vertical) support from which it is protruding. Cantilevers can also be constructed with trusses or slabs. When subjected to a structural load, the cantilever carries the load to the support where it is forced against by a moment and shear stress.^[1]

Cantilever construction allows for overhanging structures without external bracing, in contrast to constructions supported at both ends with loads applied between the supports, such as a simply supported beam found in a post and lintel system.”

I had never done one before but knew the principals involved. The thing was, the original steps had been totally irregular in the treads and risers (lengths and heights) with a very short step onto the platform. Building standards maintain that steps should (obviously) be totally regular for Health and Safety reasons. In other words, we had to start from scratch.

The treads and risers had already been ordered but large slabs came for the winders (triangular turning treads) so we made templates based on our calculations and with careful measurement and implementation some very tidy steps were produced.

Other tradesmen came to marvel at the work. It has an MC Escher quality to it. People thought there should be steels all the way up, but the nature of cantilevers is that they are by their essence self-supporting.

Please bear in mind if you are thinking of having a cantilevered staircase that the process is expensive from the labour point of view.: only 2-3 treads and risers can be installed in a day as they need to go off (set) overnight.

The first York tread goes in. Have we got the height right? If not it will have huge implications for the finished height! There are 15 treads to install.

The first winder has gone in. I was confident we had the correct shape and angle. But the angle of return from the 2 adjacent walls was not a right angle.