Question 1

What is the ideal riser height for stairs?

Accepted Answer

The ideal riser height is 7-7.5 inches. IRC code allows up to 7.75" for residential. Most people find 7.25" most comfortable.

Question 2

How do I calculate the number of stairs?

Accepted Answer

Divide the total rise (floor-to-floor height) by your desired riser height. Round to the nearest whole number, then recalculate the exact riser height.

Question 3

What is the 17-18 rule for stairs?

Accepted Answer

The sum of one riser height plus one tread depth should equal 17-18 inches. For example: 7.5" riser + 10" tread = 17.5" (ideal).

Question 4

How wide should stairs be?

Accepted Answer

IRC requires minimum 36" for residential stairs. IBC requires 44" minimum for commercial. 42-48" is comfortable for residential.

Question 5

How many stringers do I need?

Accepted Answer

Use 3 stringers for stairs up to 36" wide, 4 for 36-48" wide. Stringers should be spaced no more than 16" apart for strength.

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