The key stair numbers (IRC R311.7)
Stairs are one of the most common reasons residential plans come back with corrections. These are the dimensions the International Residential Code commonly requires — your jurisdiction may amend them.
| Item | Typical IRC requirement |
|---|---|
| Maximum riser height | 7¾″ |
| Minimum tread depth | 10″ (nosing to nosing) |
| Nosing | ¾″–1¼″ where treads are less than 11″ deep |
| Variation within a flight | No more than ⅜″ between largest and smallest riser or tread |
| Minimum headroom | 6′-8″, measured vertically from the nosing line |
| Minimum width | 36″ clear above the handrail |
Landings and winders
- Landings are required at the top and bottom of each stair, at least as wide as the stair and at least 36″ deep in the direction of travel.
- Maximum rise between landings is limited (commonly 151″ / 12′-7″), so tall stairs need an intermediate landing.
- Winder treads need a minimum depth of 10″ measured at the walkline (12″ from the narrow side) and at least 6″ at any point.
- Spiral stairs have their own reduced dimensions and must be labeled as such.
Handrails
- Required on at least one side of each flight with four or more risers.
- Height 34″–38″ measured vertically from the tread nosings.
- Continuous for the full length of the flight (with limited exceptions at newel posts and volute turnouts).
- Graspable — e.g. a round rail 1¼″–2″ in diameter, or an equivalent profile.
- At least 1½″ clear from the wall.
Guards
- Required where the walking surface is more than 30″ above the floor or grade below, including open sides of stairs.
- Minimum height 36″ at landings and floors; on the open sides of stairs, guards are commonly allowed at 34″ measured from the nosings.
- Openings must not allow a 4″ sphere to pass (open sides of stairs are commonly allowed 4⅜″; the triangle under the bottom rail, 6″).
Our plan review flags stair, egress and other code red flags — from $99.
See plan reviewWhat to show on your drawings
Plan checkers need to verify the numbers above from the plans alone. A complete stair set usually includes:
- Number of risers and treads, with riser height and tread depth, on the floor plan.
- A stair section showing rise, run, headroom line, landing depths and handrail/guard heights.
- Stair width and landing dimensions on the plan.
- Handrail and guard notes (height, graspability, baluster spacing).
- Winder dimensions at the walkline, if any.
Frequently asked questions
What is the maximum stair riser height for a house?
The IRC commonly limits residential risers to 7¾ inches, with a minimum tread depth of 10 inches. Local amendments may differ.
What is the minimum headroom for residential stairs?
Commonly 6 feet 8 inches, measured vertically from the sloped line connecting the tread nosings.
When is a handrail required on residential stairs?
On at least one side of every flight with four or more risers, at 34–38 inches above the nosings.
How tall must a guard be?
Commonly at least 36 inches where the drop exceeds 30 inches, with openings that do not allow a 4-inch sphere to pass. Open sides of stairs have slightly different rules.
Can you fix stair comments on my permit drawings?
Yes. We add stair sections, dimensions and handrail/guard notes and answer each comment as part of our $499 Permit Correction Service.
Typical stair plan check comments
Got stair comments in your letter? Our Permit Correction Service adds the sections and dimensions and answers each comment — $499 flat for every drafting comment. More examples: common plan check comments.