# Open Riser Code Requirements
### Open riser stair code requirements
**Open riser stairs are allowed under the IRC.** The key rule is the opening between treads. Under **IRC R311.7.5.1**, an **open riser staircase** can remain open when that part of the stair is **30 inches or less above** the floor or grade below. Above that height, the opening must not let a **4-inch sphere** pass through.
This is the rule most people mean when they search for **open riser stair code**, **floating stairs code**, or **open staircase code**.
### Open riser code at a glance
| Requirement | IRC rule |
| -------------------------------- | ------------------------------------------------------------------------------------------- |
| Are open risers allowed? | Yes. Open risers are permitted on residential stairs. |
| When does the 4-inch rule apply? | When the walking surface is **more than 30 in. above** the floor or grade below. |
| Maximum opening | Must not allow a **4-inch sphere** to pass. |
| Maximum riser height | **7 3/4 in.** |
| Riser variation in one flight | No more than **3/8 in.** between the tallest and shortest riser. |
| Handrail requirement | A handrail is required on stairs with **4 or more risers**. |
| Guard requirement | A guard is required where the open side is **more than 30 in. above** grade or floor below. |
### What is an open riser stair?
An **open riser stair** leaves the space between treads open. It does not use a full vertical riser board. Many people also call this a **floating stair** or **open staircase**.
This stair style is common in modern residential design. It appears in wood, steel, glass, and cable stair systems.
### When are open risers permitted?
Under **IRC R311.7.5.1**, open risers are permitted by default. The code does not require every stair tread to have a closed riser panel.
The main limit is the stair height above the surface below:
* If that part of the stair is **30 inches or less above** the floor or grade, the opening between treads is not restricted by the 4-inch sphere rule in the same way.
* If that part of the stair is **more than 30 inches above** the floor or grade, the opening must be small enough that a **4-inch diameter sphere** cannot pass through.
The **30-inch measurement** is taken from the tread walking surface to the floor or grade directly below.
### What is the 4-inch rule for open riser stairs?
The **4-inch sphere rule for open riser stairs** applies when the stair height exceeds **30 inches** above the surface below. At that point, the vertical opening between adjacent treads must be limited so a **4-inch sphere** cannot pass through.
This rule is meant to reduce child entrapment risk. It is similar to the opening limit used in other **railing code** conditions.
### How to make open riser stairs code compliant
If your **floating stairs** are above the 30-inch threshold, use one of these approaches:
* reduce the clear opening between treads
* add a horizontal element that blocks the 4-inch sphere
* overlap nosings enough to reduce the passable opening
The stair can still look open. It does not need a full closed riser to meet code.
### Open riser stairs still need standard riser dimensions
An **open riser staircase** still has to meet normal stair geometry rules. The open design does not change the basic **stair riser code**.
Key IRC limits include:
* **maximum riser height:** **7 3/4 in.**
* **maximum variation within one flight:** **3/8 in.**
* risers can be vertical or sloped from the underside of the nosing above at no more than **30 degrees from vertical**
If risers vary too much, the stair can fail code even if the openings are compliant.
### Do open riser stairs need a handrail or guard?
Yes, often.
* A **handrail** is required on stairs with **4 or more risers**.
* A **guard** is required where the open side is **more than 30 inches above** the floor or grade below.
These are separate rules from the **open riser code requirement**. A stair can meet the 4-inch opening rule and still need a compliant handrail or guard.
### Frequently asked questions
Are open riser stairs up to code?
Yes. **Open riser stairs are code compliant** under the IRC when they meet the **30-inch threshold rule**, the **4-inch sphere limit** where required, and the normal **riser height** and **uniformity** limits.
Can floating stairs be code compliant?
Yes. **Floating stairs** can be code compliant if they meet the same rules that apply to other residential stairs. That includes riser height, riser consistency, handrail requirements, and the **4-inch sphere rule** for open risers above **30 inches**.
What code section covers open riser stairs?
The primary residential rule is **IRC 2021 Section R311.7.5.1**. Always confirm the adopted code edition and any local amendments before finalizing a design.
Do open riser stairs need closed risers?
Not always. A full closed riser is not required by default. Once the stair height exceeds **30 inches** above the floor or grade below, the opening between treads must be restricted so a **4-inch sphere** cannot pass through.
### Related pages
* [4" Sphere Rule](/code-compliance/railing-code/4-sphere-rule.md)
* [When is Handrail Required?](/code-compliance/getting-started/when-is-handrail-required.md)
* [Tread Depth and Risers](/code-compliance/stair-code/tread-depth-and-risers.md)
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