The International Building Code places restrictions on the risers (vertical piece) and treads (horizontal piece) of stairs: risers can not be more than 7-3/4” high and treads not less than 10” wide. But if a tread is less than 11” wide, then a nosing must be added this is long enough that the total of tread and nosing is 11”. So, a 10” tread would require a 1” nosing projection. The maximum riser height was reduced a few years ago from 8”; so now 8” or more is considered a problem, but 8” would be acceptable on an older stair. 

   However a stair can meet these two guidelines and still be awkward to walk. The riser to tread ratio is also important to get right. A rule-of-thumb is that two times the riser plus one tread should equal 24” to 26”. Implicit in the stair ratio is the concept that as the riser gets shorter the tread should grow, and vice-versa. It has to do with having a comfortable cadence walking up and down a stairs. 

    Also, see our blog post What is the longest stair run allowed?

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Here’s links to a collection of our other blog posts about STAIRS:

• What do home inspectors check when inspecting stairs?

• Is a landing always required at the top and bottom of stairs? 

• When is a railing required at stairs?

• What is the building code for the minimum height of stair steps (risers)? 

• When is a nosing required on a stair tread?

• What is the building code requirement for receptacle outlets at stairs and stair landings?  

• Are open stair risers acceptable?

• What is the steepest residential stair allowed?

• Why is a single step dangerous in a house?

• Do I need stairs at all exit doors from a mobile home? 

 • What is the lighting requirement for stairs?

• A light is required over a stair after how many steps/risers? 

• When is safety glass required for windows at stairs and stair landings?

   Visit our STAIRS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

Diagram - CodeCheck