The 7-11 Rule for Stair Framing Explained
If there is one absolute rule in carpentry that dictates the safety and comfort of a home, it’s the layout of the stairs. Mess up the framing, and someone gets hurt. Let's break down the golden standard: the 7-11 Rule.
What is the 7-11 Rule?
The 7-11 rule is a fundamental guideline in the International Residential Code (IRC) for building stairs. It dictates two strict parameters:
- Maximum Rise: The vertical height of a single step cannot exceed 7.75 inches (often rounded to 7 for comfort).
- Minimum Run: The horizontal depth of the tread must be at least 10 inches (often set to 11 inches to accommodate a standard tread with a nosing).
Why 7 and 11?
Human ergonomics. When the rise and run add up to roughly 17 to 18 inches, the human body can ascend and descend without altering its natural walking stride. Any steeper, and the stairs become a ladder; any shallower, and they become a tripping hazard.
How to Calculate Your Stringers
Before you ever touch a circular saw, you must calculate the total rise (the exact vertical distance from the finished lower floor to the finished upper floor). Because you cannot have unequal steps, you must divide this total distance perfectly.
If your total rise is 108 inches:
- Divide 108 by an ideal step height of 7.25 inches.
108 ÷ 7.25 = 14.89 steps.- Since you can't have a fraction of a step, round up to the nearest whole number: 15 risers.
- Divide the total height by the number of risers to get your exact riser height:
108 ÷ 15 = 7.2 inches per step.
Don't want to do the math manually?
Use our free Stair Stringer Calculator to instantly find your exact rise, run, and stringer length.
Open Stair CalculatorAccounting for Tread Thickness
The most common mistake amateur carpenters make is forgetting to subtract the thickness of the tread from the bottom riser. If your exact rise calculation is 7.2 inches, and you are using a 1-inch thick oak tread, your bottom cut on the stringer must be exactly 6.2 inches.
If you fail to do this, your first step will be 8.2 inches tall, failing inspection and creating a massive tripping hazard.