Minimum thickness of bearing walls

Q. ACI 318-19, Section 11.3.1.1 states that the thickness of bearing walls shall be greater than 1/25 the lesser of unsupported length and unsupported height. I have a wall that is 31 feet long and 12 feet tall. What does “unsupported length” mean? Does this mean that the thickness of the wall cannot be less than 15 inches?

A. The unsupported length of a wall is the length between members that laterally support that wall. These members could be columns or other walls perpendicular to the wall being considered. Section 11.3.1.1 states that the minimum thickness shall be based on the shorter of either the unsupported wall height or length. Thus, it appears that in the example you provided, the minimum wall thickness is 6 inches. For more on designing bearing walls refer to chapter 11 of ACI 318-19.

References: ACI 318-19

Topics in Concrete: 318 Building Code; Design