Stair Building Safety Formulas

In some of the old building code books, they refer to a stair building safety formula that provides users with a comfortable step.

The uniform building code a long time ago provided its users with two stair building math formulas.

1. The riser height plus the tread width should not be less than 17 1/2 inches or more than 18 inches.

2. Twice the riser height plus the width of the tread shall not be less than 24 inches or greater than 25 inches.

3. The maximum pitch angle for a set of stairs shouldn't be more than 37°.

Each one of these formulas works fine. I prefer number one over the other three and provided you with a couple of examples that can help you build a comfortable stairway.

Here's A Couple of Examples:

Stair tread width of 12 inches with risers between 5 1/4 inches and 5 3/4"

Stair tread width of 11 inches with risers between 6 1/4 inches and 6 3/4".

Stair tread width of 10 inches with risers between 7 1/4 inches and 7 3/4".

Stair tread width of 9 inches with risers between 7 3/4" and 8 inches.