When it comes to building or remodeling stairs, one of the most important considerations is the rise and run – the vertical height and horizontal depth of each step. Getting the rise and run right is crucial for stairs that are both safe and comfortable to use. But what exactly are the standard measurements for rise and run?
What is Rise and Run?
The rise is the height between each stair tread. It is measured vertically from the top of one stair tread to the top of the next. The run is the depth of the stair tread. It is measured horizontally from the edge of one tread to the edge of the next.
Rise and run are usually stated in inches. They determine the steepness and comfort of the stairs. Steeper stairs have a higher rise and shorter run, while more shallow stairs have a lower rise and longer run.
Standard Rise and Run Dimensions
Building codes and standards provide guidelines for the recommended rise and run dimensions for household stairs. However, these recommendations can vary slightly between different jurisdictions and countries.
In general, the standard rise and run for stairs is:
- Rise: Between 6-8 inches
- Run: Between 9-11 inches
This results in stair angles of between 30-40 degrees from the horizontal.
International Residential Code (IRC)
The International Residential Code (IRC) applies to residential buildings up to three stories high across most of the United States. It recommends rise and run dimensions of:
- Rise: Between 4-8 inches
- Run: Minimum of 9 inches
The IRC maximum riser height is 8 inches and minimum tread depth is 9 inches. This provides a stair angle range of 26.6-42.5 degrees.
International Building Code (IBC)
The International Building Code (IBC) is used for commercial buildings in the US. For commercial stairs, it recommends:
- Rise: Between 4-7 inches
- Run: Minimum of 11 inches
The IBC maximum riser height is 7 inches and minimum tread depth is 11 inches. This gives a narrower stair angle range of 25.5-37.7 degrees.
UK Building Regulations
The UK’s Approved Document K gives the following guidelines:
- Rise: Between 5.5-7.5 inches
- Run: Minimum of 9.5 inches
The maximum riser is 7.5 inches and minimum going is 9.5 inches. This results in a stair angle range of 29.8-39.8 degrees.
Canadian Building Code
Canada’s National Building Code (NBC) specifies:
- Rise: Between 4-7.75 inches
- Run: Minimum of 8.25 inches
The NBC maximum riser is 7.75 inches and minimum run is 8.25 inches. This gives a stair angle range of 27.8-42.5 degrees.
Australian Building Codes
Australia’s National Construction Code (NCC) requires:
- Rise: Between 3.96-7.87 inches
- Run: Minimum of 7.87 inches
In Australia, the maximum riser is 7.87 inches and minimum going is 7.87 inches. The resulting stair angles range from 20.8-42.5 degrees.
Ideal Rise and Run Dimensions
While building codes provide the acceptable range, the most comfortable and safe rise and run dimensions are:
- Rise: 6.5 inches
- Run: 10 inches
This equates to a stair angle of about 32.5 degrees from horizontal. Stairs with these dimensions reduce the risk of falls and make climbing up and down easier.
Uniformity
In addition to the recommended rise and run, building codes also require uniformity. The rise and run must remain consistent across the entire flight of stairs from top to bottom. Having different riser heights or tread depths on the same stairs poses a tripping hazard.
The rise on any stair section can’t exceed the smallest rise by more than 3/8 inches. Run variations can’t exceed the smallest run by more than 3/8 inches.
Landing Dimensions
At the top and bottom of a stairs flight, building a level landing is required. Minimum landing dimensions are typically:
- Depth – As wide as the stairs, at least 36 inches
- Length – At least as long as the stair width, usually 36-60 inches
Landings give you adequate space to start and finish climbing stairs safely.
Factors Affecting Rise and Run
When planning stairs, the surrounding architectural elements often determine the rise and run dimensions used. Here are some common factors:
Ceiling Height
The ceiling height available constrains the maximum rise you can have. With taller ceilings, you can use a greater rise per step.
Travel Distance
The total vertical travel distance needed for the stairs affects the number and size of steps required. More floor-to-floor height needs higher and narrower steps.
Opening Width
The available width for the stairs affects the minimum run you can accommodate. Wider staircases allow longer tread depths.
Headroom Clearance
Decreasing the rise gives more headroom clearance underneath the stairs. This can be important for accessibility.
Purpose
Stairs intended for primarily utilitarian use can have higher rises and shorter runs than decorative stairs focused on aesthetics.
Pitch or Slope
The overall stair pitch, or angle of inclination, combines the rise and run values. Stairs for homes typically have a 30-40 degree slope from the horizontal.
Special Considerations
When designing stairs, there are some additional rise and run considerations for specific situations:
Outdoor Steps
Outdoor steps often have shorter tread lengths and higher rises to save space. However, take care not to exceed code maximums.
Spiral Stairs
With spiral stairs, run dimensions decrease towards the center pole while rise remains constant. Minimum tread depths still apply.
Curved Stairs
For curved stairs, run length often varies from the inside to outside edge. But rise height remains equal on all steps.
Accessibility
For wheelchair accessibility, maximum rises are lower and minimum runs wider. Handrails are also necessary.
Children’s Access
Use lower rises and deeper runs for stairs kids will use regularly for safer climbing.
High Traffic Areas
Public buildings may need lower rises and deeper runs for easier climbing with heavy use.
Rise to Run Ratio
A common stair design guideline is maintaining a rise-to-run ratio between 1:1 and 3:2. This means for every 1 unit of rise, the run should be 1-1.5 units.
A rise-to-run ratio in this range results in stairs with a comfortable incline angle. Extremely steep or shallow stairs make climbing difficult.
Some common rise-to-run ratios are:
- 1:1 – Very shallow stairs best for accessibility
- 7:11 – Meets many residential building codes
- 2:3 – Recommended for outdoor steps
- 3:4 – Optimal for indoor stairs
- 3:2 – Fast flight with space constraints
Converting Slope Ratio to Dimensions
During planning, stairs are sometimes designed by specifying an overall slope ratio instead of actual rises and runs. You can convert a slope ratio to dimensions using simple math:
Example Rise and Run Calculation
Slope ratio: 3/4 (3 units rise for every 4 units run)
Target overall rise for stairs: 96 inches
Run = Rise x (Slope ratio rise fraction / Slope ratio run fraction)
Run = 96 inches x (3/4) = 128 inches
So for a 3/4 slope ratio and 96 inch rise, the run would be 128 inches.
Building Code Rise and Run Limits
Here is a summary table of the rise and run limits from residential building codes discussed above:
| Code | Maximum Rise | Minimum Run |
|---|---|---|
| IRC (US Residential) | 8 inches | 9 inches |
| IBC (US Commercial) | 7 inches | 11 inches |
| UK Regulations | 7.5 inches | 9.5 inches |
| NBC (Canada) | 7.75 inches | 8.25 inches |
| NCC (Australia) | 7.87 inches | 7.87 inches |
Conclusion
In summary, the normal rise for indoor stairs is between 6-8 inches, while the normal run is around 9-11 inches. This creates a stair angle of 30-40 degrees – the ideal for easy climbing. The rise and run should remain consistent across a flight of stairs for safety.
Building codes define maximum rise and minimum run limits to ensure stairs are not overly steep or shallow. Aim for a rise-to-run ratio between 1:1 and 3:2 for optimal comfort and accessibility. Consider the intended stair usage and surrounding architecture when selecting rise and run.
