A foundation cripple wall is 5 feet 4 inches high and uses the same 2x4 stud size and spacing as the wall above. Under 2021 IRC R602.9, which sizing check is required?
- Check the studs for the additional-story sizing requirement, rather than approving solely because they match the wall above
- BMatching the studs above is the only check at any cripple-wall height
- CAlways increase exactly one nominal size once the height exceeds 2 feet
- DReplace every cripple wall over 4 feet with masonry
Where to look it up
https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042182/2021_International_Residential_Code.pdf
Why A is correct
R602.9 requires foundation cripple studs no smaller than the studs above. Above 4 feet, it additionally requires the size needed for an additional story. Five feet 4 inches exceeds that threshold, so the added sizing check is necessary. The rule alone does not prove that every 2x4 arrangement fails; actual loads and the applicable table or approved design determine adequacy. Cripple-wall bracing remains a separate requirement. Source: https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042182/2021_International_Residential_Code.pdf