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Straight mono stringer →Cable & metal
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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
The stringer is still there. You just can’t see it.
Hidden stringer stairs, also called concealed stringer stairs, are cantilever stairs carried by a steel stringer built into a framed wall. A ¾″ steel knife plate comes through the drywall at every step and each tread slides over it. It is how we build most floating stairs in renovations, because almost any home can get one. From $58k in NJconfirm.
The stringer is a closed steel tube, usually HSS 8×4 or 10×4, running up inside a 2×6 or 6″ steel-stud wall. It is bolted at the floor and at the upper floor just like a mono stringer. The wall is then built and finished around it, and only the knife plates poke through, to be covered by the treads.
Inside the wall · stringer, studs, one knife plate per tread
The steel goes in while the wall is open, the wall is finished around it, and the treads arrive last.
The stringer is bolted at the floor and upper floor, plumbed to the stair line, and the knife plates are checked against the drawings before any drywall goes up. Studs and blocking are framed around it.
Drywall and plaster are finished around the plates, so the wall is painted once with no cut-outs later. Only clean steel blades stick out of the wall.
Pick your wall and tread width to see how we would hold the treads and what it adds. Our engineer confirms it on site.
Load: 300 lb at the free edge of the tread, plus the tread's own weight.
Nothing under the treads to hide behind. Every joint is drawn first.
A typical 10′ floor-to-floor stair. Your PE-stamped drawings set the final sizes.
| Component | Specification |
|---|---|
| Stringer | HSS 8×4 or 10×4, ASTM A500, inside the wall cavity |
| Knife plates | ¾″ steel, welded to the stringer, one per tread |
| Wall | 2×6 wood or 6″ steel studs, blocking, ⅝″ drywall or plaster |
| Treads | 3¾″ solid wood, slotted over the plate, screwed from below |
| Ends | Bolted to the floor and to the upper-floor framing |
| Loads | 40 psf, plus 300 lb at the free edge of any tread |
| Stiffness | Tread edge ≈ ⅛″ under 300 lb |
Installed prices: design, PE engineering, steel, treads, delivery and installation. Permit fees and co-op deposits are billed at cost.
Includes the new framed wall around the stringer (about $6–12k of the price). If a suitable wall is already open, the price drops accordingly. Code requirements for NYC, Long Island and NJ are on the cantilever stairs page.
Send a photo of your wall and we'll tell you what fits.
Cantilever stairs carried by a steel stringer concealed inside a framed wall. A steel knife plate comes out of the wall at every step and each tread slides over it, so nothing is visible but the treads.
Yes. Hidden and concealed stringer mean the same thing: the structural stringer is inside the wall instead of under the treads.
Not into ordinary studs. A stud wall works when a steel stringer is built inside it and the studs are framed around it. That is exactly what a hidden stringer stair is.
Usually about 6″ finished: a 2×6 or 6″ steel-stud wall with drywall or plaster on the stair side.
From about $58k installed in New Jersey and $66k in New York City for a straight 9–10′ stair, including the new framed wall around the stringer. With frameless glass about $68–86k in NJ and $76–98k in NYC.
Last. The stringer goes in while the wall is open, the wall is finished around the plates, and the treads are installed after floors and paint, so they never get damaged by other trades.
Send your floor-to-floor height, a photo of the wall and a rough plan.
