Bespoke Cantilevered StaircaseS

Cantilever is an old English word describing a structure, beam or plank that is fixed at one end with the other end reaching out into a void space, for example; a juliette balcony or a cantilevered bridge, or in our case, Cantilevered Staircases, or Floating Staircases.

A 'cantilever' beam transfers its vertical load back to a fixed support. The fixed end is where there is the most stress, and the free end is where there is the most deflection. In other words, as the load moves along the length of the beam deflection gradually increases until it reaches the end, at which point deflection is at its maximum. In simple terms, think of the old Pirate expression, 'Walking the Plank'. Captives were forced to walk along a wooden plank, cantilevered over the side of a ship. The plank is anchored to the ship's deck at one end, and the victim is made to walk out along a long plank until the deflection at the very end is so great that they tip off the plank. 

In the case of our cantilevered staircases, we need to ensure the deflection at the free end of the plank - the stair tread, is kept to an absolute minimum. To achieve this, the fixed support is a 12mm thick steel plate, resin anchored into a solid wall, with rigid steel arms bolted on to the plate to support each individual stair tread. 

Our Structural Engineers calculate the deflection based on several factors; the materials used in the construction of the staircase, the length and width of the treads, the likely maximum load, ie the weight of a person on the tread, and the position of that load on the tread. In simple terms, let's assume the average weight of a man is 13 1/2 stone or 188 kg, the tread is 900mm long and 250mm deep, and the man (the vertical load) stands on the very end of the tread. The deflection at that point would be approximately 1mm. However, in practice, the man would likely walk up the centerline of the tread, and here the deflection would be practically zero.

Utilising our Structural Engineer's calculations enables us to design an 'invisible' steel skeleton in such a way as to minimise the deflection, making it perfectly safe to walk up and down the cantilevered staircase with no discernible flex, or 'bounce'.

By the time the wall is plastered to hide the steel plate, and the Oak treads are slid over the steel arms, all you see are the Oak stair treads floating in mid air. 

Depending of the actual design plan, our cantilevered staircases, or floating staircases, start from around £20,000 for a straight flight with Oak treads and 15mm Toughened Glass balustrading topped with an Oak handrail. We can also include a matching gallery landing in to the design.