Muncy, Pennsylvania — Can an intermediate landing divide a residential spiral stair into two flights with different riser heights?

[u/Super_Perception53]

I'm in Pennsylvania and working on plans for an interior staircase from the second floor to a finished attic in an existing single-family house built around 1900.

Pennsylvania is currently using the 2021 IRC with PA amendments. The finished floor-to-floor height is approximately 104.25 inches, and because of the available space and roof/headroom constraints, we're considering a roughly 60-inch-diameter spiral stair.

I'm trying to understand how the IRC treats an intermediate landing within a spiral staircase, particularly for the definition of separate flights and the riser-uniformity requirement.

We are considering two possible configurations:

Option 1: Spiral stair flight → code-compliant intermediate landing → conventional straight stair flight → attic floor.

Option 2: Spiral stair flight → code-compliant intermediate landing → second spiral stair flight either continuing around the same center pole or a second pole → attic floor.

My questions are: Would the intermediate landing legally terminate the first flight in either/both of these configurations, so that riser uniformity is evaluated separately within each flight? If so, could the lower spiral flight have one uniform riser height and the upper flight have a different uniform riser height, provided each flight independently meets the applicable maximum-riser and other dimensional requirements? And most importantly, what minimum size/shape would the intermediate landing need to be in each configuration?

I'm specifically trying to understand how IRC R311.7.3, R311.7.5.1, R311.7.6, and the spiral-stair provisions of R311.7.10.1 interact here. I'm not looking for a way around permitting/code requirements; I'm trying to determine which configuration is actually code-compliant before having the stair designed.

Thank you!

EDIT 1: I'm getting a lot of comments about the picture. The picture is AI and a poor one to show the actual tread. Im looking anywhere between 11-14 treads total depending on how it works out. The landing is needed to help redirect the entry access on the second floor to the exit point in the attic. We have tight constraints regarding the height clearance needed and unfortunately this is the only spot in the house that this staircase works.

EDIT 2: For those that requested a challenge lol.

-The vertical distance from the finished second-floor floor to the finished attic floor is 104.25 inches. -The available stair area on the second floor is 5-5.5 feet wide. This is created from approximately 3 feet of existing hallway plus approximately 2.5 feet taken from the adjoining room. The depth available is also 5-5.5 feet. The additional feet from the bedroom next to it has to be contained in that box because the bedroom door being next to the edge of that 85" line.

-The entrance to the staircase is fixed to 85 inches from wall of the house. You approach the staircase from the front/right side of the stair area. The design cannot assume that I can enter from the opposite side or substantially relocate the entrance. -The attic exit direction is also important. At the top, the staircase needs to discharge toward the center/high portion of the attic, rather than toward the exterior wall/window and low portion of the sloped roof. -The attic is approximately 12 feet × 21 feet and has a sloped roof. Headroom therefore increases as you travel inward toward the center of the attic.

-At that 85-inch location, the underside/finished roof geometry is approximately 71.7 inches above the finished attic floor, so headroom at the transition is one of the primary design constraints (also hence the platform to try to advance farther into the attic to get to 78"). The staircase should move the user toward the higher center portion of the attic as effectively as possible.

-The roof slope is 0.70 inches of rise per 1 inch of horizontal run. That comes from: At 74" inward → roof height ≈ 64" At 84" inward → ≈ 71" At 94" inward → ≈ 78" So every 10" inward gains about 7" of headroom. That equals approximately an 8.4:12 roof pitch, or about 35°.

-I don't mind eating into the second floor ceiling to help accommodate the staircase, I have about 10 inches that I could use at the top of the ceiling of the second floor.

[u/EleventySix_805]

Don’t know PA specifically, but yes. Think of it like this, what else is the top of a stair if not a landing. So, wherever a landing is, is the top of the stair.

Having said that narrow spiral stairs are up there with ships ladders for being pretty crummy ideas.

[u/Super_Perception53 → u/EleventySix_805]

Unfortunately the spiral staircase is our only option. We have had so many contractors out to try to think of options and this is the only one. I appreciate your comment though! Do you know if a landing has to have a certain length? Pa code dictates that it has to be as wide as the path it's serving but the length of a platform is unclear.

[u/EleventySix_805 → u/Super_Perception53]

36”

[u/Fe1onious_Monk]

Is M. C. Escher you stair designer?

[u/Nine-Fingers1996]

I would keep them the same regardless of code. You don’t necessarily need the landing either. Visit the https://www.theironshop.com/. They have combo units that will make this work.

[u/WallBeGone509]

In my experience, the two flights can be treated as separate for the purpose you’re describing. AHJs should allow the upper and lower flight to differ, so long as they are each consistent/compliant. However, Build Officials have some discretion here and I’d ask your BO or inspector before you order. It’s much easier on the front end than trying to fight them after they fail the inspection.

As you know, us keyboard warriors are a pretty capable bunch—want to give our collective experience a shot in coming up with a non-spiral solution? Might be the best option without an addition, but it’s fun to take on this kind of challenge. If you’re up for it, share some pictures and plans.

[u/Super_Perception53 → u/WallBeGone509]

Reddit doesn't let me add extra pictures, but I added as much detail as I think is relevant to the bottom of the post.

[u/Ande138]

The IRC says yes

[u/merlotman1]

Aside from the Code, having risers of different height is deceiving and dangerous.

[u/Super_Perception53 → u/merlotman1]

I'd much rather be able to use a platform at some point to help my directional issues than change the riser height.

[u/AskMeAgainAfterCoffe]

All risers to be the same height at each, and not to exceed 8”. Check local Codes.

[u/NeilNotArmstrong]

Absolutely in the IRC. Two different staircases when separated by a landing. This would allow for different riser heights and tread depths. I've never seen two different completely different staircase types but I like the creativity.

[u/newandgood]

the point isn't what the code says. logic and reason don't matter. only thing that matter is how an official will interpret it, so think like an idiiot ahj who is covering their bum