International Building Code Section 1610

International Building Code 1610.1

General. Basement, foundation and retaining walls
shall be designed to resist lateral soil loads. Soil loads specified
in Table 1610.1 shall be used as the minimum design lateral soil
loads unless specified otherwise in a soil investigation report
approved by the building official. Basement walls and other
walls in which horizontalmovement is restricted at the top shall
be designed for at-rest pressure. Retaining walls free to move
and rotate at the top are permitted to be designed for active
pressure. Design lateral pressure from surcharge loads shall be
added to the lateral earth pressure load. Design lateral pressure
shall be increased if soils with expansion potential are present
at the site.
Exception: Basement walls extending not more than 8 feet
(2438 mm) below grade and supporting flexible floor systems
shall be permitted to be designed for active pressure.