Cantilever (floating) staircases
Written by Scott Jones, The Stair Guys, independent staircase measuring and sourcing specialists·Last updated
A cantilever staircase, often called a floating stair, is the one where the treads seem to grow straight out of the wall with nothing holding the open side. It is the most minimal look of all, and the one that most needs to be engineered rather than simply built, because the illusion is doing real structural work.
How it works
Each tread is fixed at one end and free at the other, which is what "cantilever" means. The support is almost always hidden: a steel stringer or a set of steel brackets built into the wall, or a steel frame behind the wall finish, that the treads slot onto or bolt to. From the room you see only the treads and, usually, a glass balustrade, so the stair reads as floating. The clever part is out of sight in the wall.
The wall is part of the staircase
This is the point people miss. On a cantilever stair the wall is structural: it has to resist the load and the leverage of every tread, all day, for the life of the house. That means not every wall will do. It usually needs a solid, properly built wall or a dedicated steel frame designed for the job, and the whole thing has to be engineered as a structure, tread fixings included. A cantilever stair is never a standard product you drop in; it is designed for the specific wall it lands on, which is also why it is at the top end on cost. Get the support or the wall wrong and a floating stair is exactly the wrong place to find out.
Cantilever or mono-stringer?
Both give a floating look, but they carry the load differently. A mono-stringer hangs the treads off a single central beam that you can see. A cantilever hides the support in the wall, so the open side is completely clear. Cantilever is the more minimal of the two and the more demanding on the wall and the engineering. Either way the safety rules are the same: guarding with gaps a 100mm sphere cannot pass, and a handrail at the right height, as on the guarding page, which is why a glass balustrade is the usual partner.
Frequently asked
What is a cantilever staircase?+
A cantilever, or floating, staircase supports each tread at one end only, usually built into the wall, leaving the open side with no visible support so the treads appear to float. A steel support in or behind the wall carries the load, which makes it a structural, engineered stair rather than a standard joinery build.
Are floating or cantilever staircases safe?+
Yes, when they are properly engineered, which is essential for this type. Because each tread is held at one end and cantilevers out, the support and the wall have to be designed for the load and leverage, and the tread fixings are critical. Done correctly it is as safe as any stair and still has to meet the same guarding and handrail rules, usually with a glass balustrade.
Do cantilever stairs need a special wall?+
Often, yes. The wall is structural on a cantilever stair, resisting the load of every tread, so it usually needs a solid, properly built wall or a dedicated steel frame designed for the purpose. Not every wall can take one, which is why a cantilever staircase is engineered for the specific wall it is fixed to rather than bought as a standard product.
Related guides
- Winder staircases: what they are and the rules that govern themA winder staircase turns a corner on tapered treads instead of a flat landing. Here is how winders work, the two rules every winder has to keep, why four winders is a harder job than three, and when a landing is the better answer.
- Types of staircase: the main shapes, and how to chooseThe main staircase types are straight, quarter-turn, half-turn, winder, spiral, helical and space-saver, with open or closed strings on each. The right one is driven by the space you have, the look you want and the budget.
- Space-saver (alternating tread) stairs: what they are and when you can have oneWhat a space-saver or alternating tread staircase is, when building regulations actually allow one, the trade-offs, and why it is a space and budget compromise rather than a premium upgrade.
- Mono-stringer and central-spine staircasesA mono-stringer or central-spine staircase carries the treads on a single central beam instead of two side strings, giving a lighter, floating look. The spine can be steel or a thick timber beam, and the treads cantilever out to each side.
- Cut string vs closed string staircase: the difference, and how to chooseA closed string staircase has a solid raking board on the outer edge that hides the ends of the treads, while a cut or open string has that edge cut to the step profile so the tread ends show. Closed is simpler and cheaper, cut is a feature with more joinery.
Ready when you are.
Free and no obligation. The Stair Guys survey the real space, never off a plan.