How much floor does a U-shaped mono stringer stair need?

For a 10-foot floor-to-floor height with the landing in the middle and a 36-inch open well, about 9 feet 11 inches by 10 feet, plus 3 feet clear at the bottom step.

What is the difference between a U-shaped stair and a switchback?

A U-shaped stair has an open well between the flights, usually about 3 feet, and a landing on the wall. A switchback puts the flights about 4 inches apart under a half-landing on a post, which saves width but loses the open well.

How much does a U-shaped mono stringer stair cost?

From $38,000 installed in New Jersey and $45,000 in New York City for a 9–10 foot stair with oak treads and a cable or rod guard. With frameless glass, $50,000–66,000 in NJ and $58,000–78,000 in NYC.

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U-ShapedMono StringerStairs

Q: Does the landing of a U-shaped mono stringer stair need a post?

Not when there is a structural wall at the turn: each spine bolts to a plate on the wall and a steel ledger carries the landing edge. Without such a wall, a slim post goes under each knee.

The full turn, held by the wall.

Two parallel flights on central steel spines, joined by a full-width landing that turns 180°. The landing bolts to the end wall, so there is no post in the room. Engineered, permitted and installed in NYC, Long Island and New Jersey, from $38k in NJ.

Size my stair →Explore the turn

PE-stamped engineering
NYC & NJ permits handled
Installed in about 4 days

U-shaped mono stringer stair: oak treads on a black steel spine rising to a full-width oak landing on the travertine end wall, then turning back along a concrete wall to the upper floor

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What it is

Turn all the way around. Keep one clean line.

A U-shaped mono stringer is two straight flights side by side, each carried by one central steel spine, joined by a landing that runs the full width of both flights. You climb, turn 180° and climb back. Both spines turn level under the landing and bolt to the end wall, with a hidden steel ledger along its edge.

180°One full turn

2Spines, no post

≈ 10′ × 10′Footprint at 10′ floor height

Underside of the U landing: both black steel spines turn level and bolt to the end wall on steel plates, with a ledger along the wall

The wall connection · two spines, two wall plates, one ledger

Scroll to assemble

Two flights. One full turn.

01 · Spines and the wallTwo closed steel tubes with welded V brackets. Each turns level under the landing and bolts to a plate on the end wall. A steel ledger carries the landing edge.
02 · Treads, then the landingSolid 3¾″ oak, flight by flight. The landing spans both flights and the well, about 42″ × 10′, on seat plates over both spines.
03 · Glass around the wellFrameless panels follow each flight and close the open well at the landing: 36″ in NJ, 42″ in NYC.

Two ways to turn back.

Both stairs climb, turn 180° and climb back. The gap between the flights decides how wide the stair is, how it is held up and how it feels to walk. The orange line is the path your feet follow.

Plan · U with open wellScale ≈ 1:50

01The U with an open well

The flights sit about 3′ apart, so light and sightlines run straight down the middle. The landing spans both flights and the well and bolts to the end wall, with no post in the room. Every tread is a full 11″.

The most open, sculptural turnNo post: the wall carries the landingNeeds about 10′ of width

Size a U-shaped stair ↓

Plan · SwitchbackScale ≈ 1:50

02The switchback

The flights run side by side with only a 4″ gap, under one half-landing on a slim post. It saves about 2′-8″ of width, but there is no open well, and the two spines sit close enough to read as one mass.

Narrowest 180° turnWorks without a structural wallNo open well

Switchback mono stringer stairs →

Both plans: 10′ floor to floor, 42″ treads, 7½″ risers, landing in the middle. Configuration is confirmed against your space and the code that applies there.

Full-width oak landing of a U-shaped mono stringer seen from above, with glass closing the open well and both flights leaving it in parallel

Landing on the wall

Glass at the well

Two spines, in parallel

The landing, in detail

Every junction, considered.

The landing, the wall connection, the glass around the well and the handrail are drawn together as one design, not added on site.

A solid oak landing about 42″ × 10′, on seat plates over both spines. Each spine bolts to a plate on the end wall, and a steel ledger along the wall carries the landing edge. No post in the room.
Sloped panels follow both flights along the 3′ well. A level panel closes the well at the landing edge, so a child can never reach the drop. 36″ high in NJ and on Long Island, 42″ in NYC.
The second flight leaves the landing on its own spine, running back parallel to the first, each centred under its treads. On the wall side a handrail runs the full flight, 34–38″ above the nosings.

Designed around your space.

Pick your floor height, where the landing sits, how wide the well is and which way you turn. The plan and the numbers redraw to the same rules our engineer uses.

Plan · 10′ · turn left · landing in the middleLive

Floor to floor

Landing sits

Open well

Turn

Location

Risers: 16 × 7½″
Treads: 7 + landing + 7
Landing at: 5′-0″
Length: 9′-11″
Width: 10′-0″
Well guard: 36″

HeightFinished floor to finished floor sets the total rise and the number of steps.
FootprintTwo 42″ flights plus the well set the width. The longer flight plus the 42″ landing sets the length. Add 3′ clear at the bottom step.
End wallThe landing bolts to the wall at the turn. Concrete, masonry or a framed wall with new blocking all work. No wall there? We add a slim post under each knee.
OpeningThe stairwell opening covers most of the footprint, about 9′-11″ × 10′-0″, with the upper floor meeting the top step.

Under the landing there is about 3′-2″ clear: not enough to walk under, enough for storage or a bench.

How the load travels.

A straight mono stringer needs only its two ends. A U has three supports: the floor, the end wall at the landing and the upper floor. Tap a step to follow the weight.

Developed elevation · both flights unfolded10′ · illustrative

Reactions are for a typical 10′ U in white oak and are illustrative. A licensed PE sizes every connection for your stair, your wall and your floor.

Close-up under the U landing: two black steel spines turn level and bolt to plates on the end wall, with the landing ledger above

Component	Specification
Spines	Two closed steel tubes, HSS 10×6 typical, each turning level under the landing
Wall connection	¾″ plate per spine, through-bolted or epoxy-anchored into concrete, masonry or new blocking
Landing support	Seat plates on both spines plus a steel ledger along the end wall. Post option where there is no structural wall
Landing	Full width of both flights and the well, about 42″ × 10′ × 3¾″ solid wood
Open well	12–48″ between the flights, 36″ standard
Treads	42″ × 11″ × 3¾″, 18″ past the spine each side
Rise × run	7–7½″ × 11″, about 33°. Open riser gap ≤ 3¾″
Top	¾″ header plate, through-bolted. A moment connection, not a hanger
Loads	40 psf, plus 300 lb on any tread or landing corner
Stiffness	L/480 per flight, first frequency 8–10 Hz or more

Wall or postsA concrete or masonry end wall carries the landing with nothing in the room. A framed wall gets new blocking or a steel channel. No wall at the turn? Two slim posts under the knees.

Fits through the doorEach spine is short, about 9–11′, so a U gets into a brownstone or up an elevator more easily than one long straight spine.

Tall floorsThe landing splits the rise in two, so a U keeps every flight under the NYC 12′ limit up to about 24′ floor to floor.

A palette of quiet distinction.

Choose the tread species, the spine finish and the lighting as one coordinated palette. The landing is made from the same boards as the treads, laid in the same direction.

White oak treads and landing on the black steel spines of a U-shaped stair — **White oak**Light, even grain · natural oil

Walnut treads and landing on a black steel spine — **American walnut**Deep and warm · +$2–4k

Smoked oak treads and landing on a black steel spine — **Smoked oak**Fumed, mid-brown

Spine finishMatte blackWhiteBronzeGraphiteMetal finishes →

Matte black spines bolted to the end wall under an oak landing

White powder-coated spines bolted to the end wall under an oak landing

Bronze powder-coated spines bolted to the end wall under an oak landing

U-shaped mono stringer at night with warm LED light under every tread and the landing

Lighting · designed and installed by us

Light all the way round

An LED channel under the nose of every tread and the landing edge, wiring hidden inside both spines and run out through the wall plate, one dimmable driver. Motion sensors and tunable white are options. +$2–4.5k.

Your electrician brings power to one box behind the wall plate. We do the rest.

Under-tread stair lighting →

Frame the view.

The railing sets how open the stair feels and what your hand holds. In a U it also closes the well: guards run along both flights on the well side and across the landing edge.

Frameless glass guards on standoffs along both flights and across the open well of a U-shaped stair — **Frameless glass**½″ on stainless standoffs · most chosen

Stainless cable guard with black posts around the well of a U-shaped mono stringer — **Cable**Fine horizontal lines · lowest cost

Black vertical rods with a flat top rail around the well of a U-shaped mono stringer — **Black rods**Vertical rhythm that matches the spine

Gaps under 4″ everywhere. All railings → · Glass railings → · Cable railings →

From your plans to a considered proposal.

01Share drawingsFloor plans, floor-to-floor height and photos of both ends of the stair.
02Resolve the layoutWe set the well, check the end wall and send a 3D concept within a week.
03Engineer & permitPE-stamped drawings, NYC DOB NOW or your NJ town, co-op packages.
04Fabricate & install6 weeks in our shop, then 3–4 days on site. Glass 2–4 weeks later.

What shapes the investment?

Floor height and width, the well, the end wall, tread species, how much glass, finishes, lighting and site conditions.

See prices ↓

Installed in about 4 days.

Two more days than a straight stair: the wall plates and ledger go in first, then the landing, then each flight. Full timeline →

Day 1–2Wall plates & spinesWall plates and ledger anchored, header plate bolted up, both spines set and leveled.
Day 3Landing & treadsLanding on its seat plates and ledger, then the treads of each flight, fixed from below. Wall handrail.
Day 4Lighting & touch-upsLED drivers connected, powder coat touched up, site cleaned.
+2–4 weeksGlassMeasured once the spines are set, installed in a day.

What it costs.

Installed prices: design, PE engineering, fabrication, powder coat, delivery and installation. Permit fees and co-op deposits are billed at cost.

U-shaped mono stringer with black rod guard

Mono U · full landing

NJfrom $38k

NYCfrom $45k

9–10′ floor to floor, 14 treads + landing
White oak, 42″ × 3¾″, natural oil
Matte black spines, landing on the wall
Cable or black rod guard

U-shaped mono stringer with frameless glass guards around the well

Mono U Glass · most chosen

NJ$50–66k

NYC$58–78k

Same stair
Frameless ½″ glass on both flights and across the well
Glass around the upper-floor opening
Walnut or another species on request

Less width?

Close the well with a switchback, or turn once with an L-shaped stair.

Switchback saves about 2′-8″ of width
An L needs about 10′ × 10′ too, but on two walls

What moves the price	Effect	What moves the price	Effect
LED under every tread + landing	+$2–4.5k	Walnut treads + landing	+$2.5–5k
Posts instead of a structural end wall	+$1–2k	Brushed stainless spines	+40–60% on steel
Glass on the outer side of flight 1	+$3–6k	Heights over 12′	+$1–1.5k per tread

The full-width landing, second spine and well guards add about $6–10k over a straight mono stringer. Full cost breakdown →

Code for a U-shaped stair

	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″
Landing depth	At least the stair width in the direction of travel, across the full width of both flights. Our standard: 42″ deep
Max rise of one flight	12′-7″	12′-7″	12′-0″
Headroom, incl. over the landing	6′-8″	6′-8″	80″
Guard along the flights	36″	36″	34″
Guard at the landing, well & opening	36″	36″	42″
Openings in the guard (well side)	A 4″ sphere must not pass. Cable runs need posts close enough to keep tension

An open stair joining 3–4 floors of an NYC townhouse may also need sprinklers. Are floating stairs legal in NYC? →

Our promise.

A floating stair is a big decision. Here is what we put in writing.

Fixed price after the measureOnce we measure your space, the price is locked. No change orders for anything we should have seen.

10-year structural warrantySpines, wall plates, ledger, brackets and connections. 2 years on installation, 5 on the finish, and a free first-year check-up.

PE-stamped, permits handledA licensed engineer stamps every stair. We file with NYC DOB NOW or your NJ town and prepare co-op packages.

Licensed and insuredNJ Home Improvement Contractor #confirm · general liability and workers’ comp, certificates for your building.

Dates you can plan aroundFabrication in 6 weeks from approved drawings, an install of about 4 days, and a dated schedule in your contract.

Pay as it gets built50% to start engineering, 40% before delivery, 10% only when you sign off on the finished stair.

For architects & designers

U-shaped stair details with a wall landing

Standard U details as a starting point: base, knee, wall plate, landing ledger and header. We produce PE-stamped shop drawings for your approval.

White architectural model of a U-shaped mono stringer stair with a full-width landing — Parametric model: the same geometry as your shop drawings.

A U-shaped mono stringer seen across the room: two parallel flights, the open well between them and the oak landing on the end wall

Turn around.
Keep the line.

Before we begin.

Still unsure? Send a photo of your stairwell and we'll tell you what fits.

What is a U-shaped mono stringer stair?

Two straight flights side by side, each on one central steel spine, joined by a landing that runs the full width of both flights. You climb, turn 180° and climb back. Both spines turn level under the landing and bolt to the end wall.

Will it fit my space?

For a 10′ floor-to-floor height with the landing in the middle and a 36″ well, the stair needs about 9′-11″ × 10′-0″ of floor, plus 3′ clear at the bottom step. Use "Designed around your space" above for your height.

Does the landing need a post?

Not when there is a structural wall at the turn. Each spine bolts to a plate on the wall and a steel ledger carries the landing edge. If the end wall cannot take it, we add a slim post under each knee. Our engineer decides from your site.

U-shaped or switchback: what is the difference?

A U has an open well between the flights, usually about 3′, and a landing on the wall. A switchback puts the flights 4″ apart under a half-landing on a post. It saves width but loses the open well. See switchback mono stringer stairs.

Is the open well safe for children?

Yes, when it is guarded. Glass, cable or rods run along both flights on the well side and across the landing edge, with no gap a 4″ sphere can pass. In New York City the guard at the landing and the opening is 42″.

Will it bounce at the turn?

Not when it is sized right. Each flight is short, each knee is a welded moment connection and the wall takes the landing directly. We design for L/480 and 8–10 Hz or more.

How much does a U-shaped mono stringer cost?

From $38k installed in New Jersey and $45k in New York City for a 9–10′ stair with oak treads and a cable or rod guard. With frameless glass, $50–66k in NJ and $58–78k in NYC.

What should I share for a price?

Floor plans, the floor-to-floor height, what the end wall is made of and photos of where the stair starts and arrives. A rough sketch with dimensions is enough to start.

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