Stair Construction

                 Attention Builders and Contractors:

                           Stair Construction

The Georgia Department of Community Affairs Amendment to Section R311 of the International Residential Code regarding stair construction will expire January 1, 2010. Stair construction for residential permits issued after December 31, 2009 shall comply with section R311 as written. See highlighted changes below.

R311.5.3.1 Riser height.

• The maximum riser height shall be 73⁄4 inches (196 mm).
• The riser shall be measured vertically between leading edges of the adjacent treads.
• The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3⁄8 inch (9.5mm).

No allowance for variance of ¾” for first and last riser.

R311.5.3.2 Tread depth

• The minimum tread depth shall be 10 inches (254 mm).
• The tread depth shall be measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread’s leading edge.
• The greatest tread depth within any flight of stairs shall not exceed the smallest by more than 3⁄8 inch (9.5 mm).
• Winder treads shall have a minimum tread depth of 10 inches (254 mm) measured  as above at a point 12 inches (305 mm) from the side where the treads are narrower.
• Winder treads shall have a minimum tread depth of 6 inches (152 mm) at any point.  
• Within any flight of stairs, the largest  winder tread depth at the 12 inch (305 mm) walk line shall not exceed the smallest by more than 3⁄8 inches (9.5 mm).

Minimum Tread depth changed from 9” to 10.”