Cantilevered Staircases

Cantilever is an old English word describing a beam, or plank that is fixed at one end, with the other end reaching out into a void space. 

In simple terms, think of the old Pirate's method of execution - 'Walking the Plank' when captives were forced to walk along a wooden plank, cantilevered over the side of the ship. The plank was fixed to the ship's deck at one end, and the victim made to walk out along the plank until the deflection at the very end was so great that they tipped off  ... SPLASH!!!

(illustration opposite by Howard Pyle for Harper's Magazine, 1887)

In the case of our cantilevered staircases, it's essential to ensure the deflection at the free end of the plank - the stair tread, is kept to an absolute minimum, and in order to achieve this, we use an invisible steel skeleton.

Our patented system consisting of 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.

The Engineering Behind The Illusion

Cantilevered staircases create a 'floating illusion', but their visual lightness belies a robust structural framework. These cantilevered designs rely on precise engineering to safely transfer loads from each tread into a secure wall, or support structure. Unlike traditional staircases, with visible stringers or supports underneath, cantilevers embed treads directly into a load-bearing wall to resist bending and shear forces.

A cantilever stair tread transfers its vertical load back to the fixed support. That 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 tread, deflection gradually increases until it reaches the end, at which point deflection is at its maximum.

Structural Engineers calculate the deflection

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. 

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  less than 1mm. However, in reality, the man would walk up the centerline of the tread, not the far edge, and here the deflection would be practically zero, and imperceptible to the person on the staircase.

Utilising our Structural Engineer's calculations enables us to design an 'invisible' steel skeleton in such a way as to virtually eliminate the deflection altogether, 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 magically floating in mid air.

Materials and Finishes for Floating Staircases

The choice of materials plays a significant role in both the appearance and performance of a floating staircase. Our clients favour a combination of timber, glass and metal to achieve a balanced and contemporary look.

We use Oak for the treads, due to its durability and attractive grain, and because it's a now a commercially grown crop with more trees planted each year than are harvested. It can also be finished in a range of colours, from light and natural or 'Limed', to darker, richer shades, allowing the staircase to complement existing flooring and furniture.

Glass is commonly used for balustrades, providing safety while maintaining transparency. Toughened and laminated glass ensures strength and compliance with regulations, making it suitable for family homes. Frameless glass panels are particularly popular as they enhance the floating effect.

Metal components, typically steel, form the hidden structure of most floating staircases with some clients opting for wrought iron spindles for the balustrading rather than glass, and these can be powder coating to any RAL colour.