How the Loretto Staircase Works: The Engineering Explained
The Loretto staircase doesn’t defy physics — it’s a clever, fully explainable piece of structural engineering. The short version: instead of resting on a central pole, the entire helix behaves like a coiled spring, carrying its load down two spiral beams (the stringers) into just two anchored points, the floor and the choir loft. Here is exactly how that works.
How does a spiral staircase stand with no center pole?
A conventional spiral staircase hangs its steps off a central column (a newel post) that carries the load straight to the floor. The Loretto staircase has no such column. Instead, the load travels through its two stringers — the continuous spiral beams that run up each edge of the stair. Each stringer is bent into a helix, and both are anchored firmly at the bottom (the chapel floor) and the top (the choir loft). The stair effectively hangs and braces between those two points.
The hidden “almost-pole”: the inner stringer
Here is the single most important structural fact, and the one most stories skip. The inner stringer’s radius is so small that, in the words of wood technologist Forrest N. Easley, it “functions as an almost solid central pole.”
In other words, the staircase isn’t supported by nothing in the middle — the inner spiral beam is wound so tightly that it does much of the job a center post would. This is the real engineering answer, and — tellingly — it’s also the skeptics’ best evidence. We follow that thread on the debunked-or-miracle page.
The stringers as a helical beam
The treads and risers are rigidly joined to the two stringers, so the whole assembly behaves as one torsionally stiff, tube-like structure rather than a stack of loose steps.
As you climb, your weight is distributed around the circumference of the helix and funneled into the two bearing points.
Structural engineers recognize this as standard helical-beam (or curved-stair diaphragm) behavior — unusual to see executed so cleanly in wood, but not mysterious.
The “Slinky” or spring analogy
A helix stores and redistributes load much like a compressed spring — which is why a tightly coiled stair can feel springy yet remain stable.
It’s a genuinely useful mental model: like a Slinky standing on its end, the coil resists being compressed because the load is shared all the way around the spiral rather than dumped onto one point.
Pegs, not nails — and the glue question
The staircase is held together with wooden pegs in drawbore-style joinery rather than iron nails. That’s a deliberate, sound choice: wooden pegs swell and shrink with the surrounding wood as humidity changes, where iron nails would loosen and rust over time. On the “no nails” point, the sources agree.
Contested: is there also glue?
The sources directly contradict each other on whether the curved stringers are also bonded with wood glue into a laminate. Rather than smooth this over, here is the conflict laid out:
| Source | Claim |
|---|---|
| Wikipedia | Held by wooden pegs; no glue and no nails |
| Carpenter / “Mysterious New Mexico” analysis (recycled by several travel blogs) | The stringers are built from overlapping wood segments joined with wood glue to form a curved laminate |
| Loretto Chapel’s own marketing | Built with “no nails or glue” |
How to read it: the “no nails” claim is well supported. The glue question is unresolved in the public record — a laminated-segment construction is plausible engineering and would explain the smooth curves, but the chapel and Wikipedia both say no glue. No published source settles it with primary evidence, so we present it as open rather than pick a confident answer.
Is it safe to walk on?
It was originally built without a railing — one was added later for safety, and at some point an iron bracket was also fitted to tie the stair to a nearby loft column.
There is real load evidence that it works: a photograph from around 1959 shows at least twenty choir members standing on the staircase at once.
Today visitors view it but no longer climb it, to preserve the structure. More on the railing and the bracket is on the debunked-or-miracle page.
Keep exploring
- Back to the Loretto Chapel staircase overview
- Who built it?
- What wood is it made of?
- Debunked or miracle? Every claim vs the evidence
- The trait method: how it was laid out by hand
Researched & fact-checked by the Loretto Volunteers Editorial Team
Loretto Volunteers is an independent research project documenting the history, architecture, and enduring mystery of the Loretto Chapel staircase. We work from primary and archival sources and show our evidence. Last reviewed: June 2026.