Stair systems
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Straight mono stringer →Cable & metal
Wood & combinations
Frameless glass →Tread profiles
Solid white oak →Stair lighting
Light under every tread →Who we work with
Stair systems
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All floating stairs →Tread materials
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Specifications
Nothing under the treads but air.
Cantilever stairs are floating stairs whose treads come straight out of the wall, with no stringer, posts or brackets you can see. Each tread is held by steel hidden inside the wall, which takes about 1,000 ft-lb of load at every step. Designed, engineered, permitted and installed in NYC, Long Island and New Jersey, from $52k in NJconfirm.
A cantilever staircase has no structure in the room. Every tread is a short steel beam wrapped in wood, fixed at one end inside the wall and free at the other. Nothing runs under the treads, so light, sightlines and the floor below stay completely open. The trick is the wall: it has to hold every step like a shelf holds weight at its edge.
Where the tread meets the wall · no brackets, no plates, no gaps
The steel is the same idea in every case: a stiff steel core inside each tread, locked into something strong inside the wall. What changes is the wall.
A steel tube runs up inside the wall like a mono stringer turned on its side, bolted at the floor and at the upper floor. A ¾″ steel knife plate is welded to it at every step and passes through the drywall. Each tread slides over its plate. This is the method we use most in renovations.
Where the wall is poured concrete or reinforced, grouted block, each tread gets a steel core plate and three or four threaded rods set in epoxy 6–8″ deep. We scan for rebar first, and in NYC an inspector checks every anchor.
Pick your wall and your tread width. You will see how we would hold the treads, what has to change and roughly what it adds. Our engineer confirms it on site.
Load: 300 lb at the free edge of the tread, the code's concentrated load, plus the tread's own weight.
A cantilever stair has nothing to hide behind. Every edge, joint and shadow line is drawn first.
Straight is the purest. Turns and landings need a wall on two sides, a slim post or a hanger from above, because a landing is a much bigger cantilever than a tread.
Every cantilever tread has steel inside: a knife plate or a core plate the wood slides over. The wood you see is solid and 3½–4″ thick, so the open riser gap stays under 4″.
Also in solid steel or steel box treads (thinner, 2–2½″) and in stone over a steel core on concrete walls. All treads → · White oak treads →
The open side needs a guard. The wall side needs a handrail you can grip, 34–38″ high: a glass panel is a guard, not a handrail, so a cantilever stair always has both.
Gaps under 4″ everywhere. Glass railings → · Wall-mounted handrails →
The steel goes in while the walls are open. The treads go on after floors and paint, so they never get damaged by other trades.
Installed prices: design, PE engineering, steel, treads, delivery and installation. Wall work depends on your wall and is quoted after we see it. Permit fees and co-op deposits are billed at cost.
| What moves the price | Effect | What moves the price | Effect |
|---|---|---|---|
| LED under every tread | +$1.5–4k | Walnut treads | +$2–4k |
| Landing (L or U) | +$6–12k | Stone treads on steel | quoted |
| Masonry liner wall | quoted | Heights over 12′ | landing required |
A cantilever costs more than a mono stringer because every tread is its own engineered beam and the wall must be built or checked around it. Cantilever stairs cost guide →
| New Jersey · 1–2 family 2024 IRC as amended | Long Island NYS Residential Code | New York City · R-3 2022 NYC Building Code | |
|---|---|---|---|
| Max riser · min tread | 8¼″ · 9″ | 8¼″ · 9″ | 8¼″ · 9″, and 2 risers + 1 tread ≤ 25½″ |
| Max rise of one flight | 12′-7″ | 12′-7″ | 12′-0″ |
| Open risers | A 4″ sphere must not pass between treads, so a 7½″ rise needs a tread at least 3½″ thick | ||
| Handrail | 34–38″, continuous, on the wall side. Glass is a guard, not a handrail | ||
| Guard along the flight | 36″ | 36″ | 34″ |
| Guard at the floor opening | 36″ | 36″ | 42″ |
| Anchors in concrete | Per engineer | Per engineer | Special inspection of adhesive anchors |
An open stair joining 3–4 floors of an NYC townhouse may also need sprinklers. Are floating stairs legal in NYC? →
A floating stair is a big decision. Here is what we put in writing.
Typical plan and section, wall build-ups for framed, concrete and CMU walls, knife-plate and anchor details. We produce PE-stamped shop drawings and coordinate the wall with your structural engineer.
Still unsure? Send a photo of your wall and we'll tell you what it can carry.
Floating stairs whose treads are fixed only at the wall and project into the room, with no stringer, posts or brackets underneath. Each tread has a steel core locked into steel hidden in the wall.
Each tread works like a shelf bracket: the load at its free end becomes a bending moment at the wall, about 1,000 ft-lb for 300 lb on the edge of a 42″ tread. A steel knife plate or core plate inside the tread carries that moment into a hidden steel stringer or into anchors in a concrete wall.
From about $52k installed in New Jersey and $60k in New York City for a straight 9–10′ stair with oak treads and a cable or rod guard. With frameless glass about $62–80k in NJ and $70–92k in NYC. A new framed wall with a hidden stringer adds about $6–12k.
No. Poured concrete and reinforced, grouted block can take anchors directly. A framed wall works when it is built around a hidden steel stringer. Ordinary drywall partitions and old brick cannot hold the treads on their own.
Yes, but usually not into the old brick itself. We build a new framed or concrete liner wall in front of the brick and hide the steel in it. If the brick is a party wall, it also belongs to your neighbor, so we do not drill through it.
Yes. An L-shaped stair can carry its landing on two walls in a corner. Otherwise the landing needs a slim post or a hanger from above, because a landing is a much bigger cantilever than a tread.
Not when they are engineered right. Each tread has a steel core sized so its edge moves about ⅛″ under a 300 lb load, stiffer than the code asks.
Usually 3½–4″ of solid wood over a steel core for a 36–42″ tread. Steel treads can be 2–2½″. The thickness also keeps the open riser gap under 4″, as code requires.
A cantilever has nothing in the room but needs a strong or new wall. A mono stringer has one central spine and works anywhere, even in the middle of a room, and usually costs less. See cantilever vs mono stringer.
Your wall and tread width from above are already filled in. Add a photo of the wall and your floor-to-floor height.
