Question 1

What is the ideal riser height for stairs?

Accepted Answer

The ideal riser height is 7-7.5 inches (178-190mm). IRC building code requires risers to be no more than 7.75 inches and no less than 4 inches. All risers must be consistent within 3/8 inch of each other.

Question 2

What is the minimum tread depth required by code?

Accepted Answer

The International Residential Code (IRC) requires minimum 10-inch tread depth measured from nosing to back. Commercial stairs typically require 11 inches. The 7-11 rule suggests 7-inch risers with 11-inch treads for optimal comfort.

Question 3

How do I calculate stringer length?

Accepted Answer

Use the Pythagorean theorem: Stringer Length = √(Total Rise² + Total Run²). Total Run = Number of Treads × Tread Depth. Add extra length for top and bottom connections when cutting actual stringers.

Question 4

What is the proper angle for residential stairs?

Accepted Answer

Safe, comfortable stairs typically have angles between 30° and 37°. Stairs steeper than 40° are uncomfortable and may violate building codes. Shallower stairs require more horizontal space but are easier to climb.

Question 5

How many risers do I need?

Accepted Answer

Divide total rise (floor-to-floor height) by desired riser height, then round to the nearest whole number. For example: 108 inches ÷ 7 inches = 15.4, so use 15 risers. Actual riser height = 108 ÷ 15 = 7.2 inches.

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