Stair Headroom
Checker
Compare one measured vertical clearance with the IBC 2024 §1011.3 threshold. The result tests headroom only and does not determine stair compliance.
Who it's for: architects and code consultants checking stair headroom at construction documents or during a permit review.
How to use this calculator
The formula
The baseline is 80 inches (2032 mm). The §1011.3 exception permits 78 inches for spiral stairways complying with §1011.10.
Worked example
When this estimate will be off
- Only one clearance value is checked. The code requires the 80-inch minimum maintained at every point across the full stair width and one tread depth beyond the bottom riser — a single-point measurement may miss a localized obstruction.
- Alternating-tread devices (IBC §1011.11) and ships ladders (§1011.15) have separate, lower headroom provisions. Use this checker only for conventional and spiral stairs.
- Local code amendments or occupancy-specific provisions may impose a higher minimum than the IBC/IRC baseline. Always confirm against the adopted edition and any local amendments.
- Headroom is only one stair parameter. Code compliance also requires checking riser height, tread depth, handrail height, guards, and egress width as independent checks.
Frequently asked questions
A common mistake: Only one clearance value is checked. The code requires the 80-inch minimum maintained at every point across the full stair width and one tread depth beyond the bottom riser — a single-point measurement may miss a localized obstruction.
IBC §1011.3 requires a minimum of 80 inches (2032 mm) measured vertically from the plane of the tread nosings to the lowest overhead obstruction. This clearance must hold across the full stair width and extend one tread depth beyond the bottom riser. Spiral stairs are permitted 78 inches under §1011.10.
Headroom is measured vertically — not perpendicular to the slope — from an imaginary plane connecting the tread nosings up to the lowest obstruction directly above. Critical check points are the top of the run (where a beam or floor edge often encroaches), every point across the stair width, and one tread depth beyond the bottom riser.
No. It is deliberately limited to the unamended 2024 model IBC. A residential-code analysis must use the applicable adopted IRC edition separately.
Not without code approval. If a beam or duct drops below 80 inches above the nosing plane, options include raising the obstruction, lowering the stair run by reducing riser height or adding a landing, or rerouting the duct. A variance or alternate means of compliance is required when structural constraints prevent the full 80-inch clearance.
Sources
- ICC 2024 IBC §1011.3 — 80-inch stair headroom and listed exceptions
- ICC 2024 IBC §1011.10 — conditions for spiral stairways
Sources and review record
Sources and method basis
- IBC 2024 §1011.3 and the spiral-stair exception tied to §1011.10
- https://codes.iccsafe.org/
Limitations
- Compares one measured vertical clearance with one selected headroom threshold only.
This free Stair Headroom Checker is built and maintained by DataDrivenAEC, using the relevant codes and standards. It does not substitute for professional judgment.