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Stair and guard code quick check
IRC 2021 R311.7, R312 — check your local code
The numbers residential stairs and guards are checked against, from IRC 2021 R311.7 and R312: riser and tread limits, nosing, headroom and width, handrail height and size, and guard height and openings.
Many jurisdictions amend the IRC: check your local code. The stair calculator checks a layout against these numbers as you plan it.
Verify with your local code and AHJ. Reference only, no warranty.
Steps
| Riser height | max 7 3/4″ |
| Tread depth | min 10″ |
| Biggest difference, riser to riser or tread to tread | max 3/8″ |
| Nosing, when the tread is under 11″ | 3/4–1 1/4″ |
| Rise of one flight | max 151″ |
Room to walk
| Headroom | min 6′ 8″ |
| Stair width | min 36″ |
| Clear width at the rail, one handrail | min 31 1/2″ |
| Clear width at the rails, two handrails | min 27″ |
| Landing, in the direction you walk | min 36″ |
Handrail
| Needed from | 4 risers |
| Height above the nosings | 34–38″ |
| Round rail diameter | 1 1/4–2″ |
Guard
| Needed where the drop is | over 30″ |
| Height at a floor or deck | min 36″ |
| Height on a stair, above the nosings | min 34″ |
| Gaps: a ball this size can't pass | 4″ |
| Gaps on the open side of a stair | 4 3/8″ |
| Triangle at riser, tread and bottom rail | 6″ |
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Questions
What is the maximum stair riser height?
max 7 3/4″ under IRC 2021 R311.7. Check your local code.
What is the minimum stair tread depth?
min 10″, nosing to nosing.
How high should a stair handrail be?
34–38″, measured above the nosings.
What is the minimum stair headroom?
min 6′ 8″, measured plumb from the nosing line (IRC 2021 R311.7).