Opening length

Is my stair opening long enough?

A short ceiling or floor opening can make the stair path fail in the real room even when the rise/run math looks acceptable.

The short answer

The current planning check flags opening length shorter than the calculated stair run.

StairSolver uses this as a baseline planning check. If the measurement crosses the threshold, the report explains what number triggered the flag and what to ask before building, buying, or approving a plan.

Report boundary

Baseline risk, not local approval.The local authority, inspector, engineer, or qualified stair professional still decides the final answer for the exact property.

What StairSolver checks

Inputs used for this warning

ceiling or floor opening length
calculated stair run
headroom path

User input fields: ceiling or floor opening length, floor-to-floor height, clear floor length.

Why it matters

What problem this prevents

Basement, attic, and remodel stairs often look possible in plan view until the user checks where the stair passes under the floor opening.
A short opening does not automatically prove failure, but it is a strong reason to verify headroom on the exact layout before framing or cutting stringers.

What to ask before building

Questions generated from this risk

Can the plan show where the stair passes under the floor opening and where minimum headroom is measured?
Can the contractor mark the opening edge, stair run, and lowest headroom point before framing?

Which official source is referenced?

Source citations

2021 IRC R311.7.2

Headroom has to be verified along the stair path; a short ceiling or floor opening is a planning red flag that needs layout confirmation.

International Code Council / irc-baseline-2026-07-01Open 2021 IRC R311.7.2

What this page cannot prove

Where the tool stops

It cannot say your local inspector will approve the stair.
It cannot prove the actual headroom path without the opening position, framing, finish thickness, and site measurements.