IBC 2009 live load reduction is specified in code section 1607.9. Live load effects on members with influence areas of less than 400 square feet are not modified by live load reduction.

IBC 2009 requires that live loads in excess of 100 psf and live loads from passenger car garages shall not be reduced, except that members supporting two or more floors may be reduced up to 20% per code sections 1607.9.1.2 and 1607.9.1.3. These two load types must be drawn on a "Live (storage)" loading to be considered appropriately.

IBC 2009 requires that live loads of 100 psf and at areas where fixed seats are located in Group A occupancies cannot be reduced per section 1607.9.1.4. These loads must be drawn on a "Live (unreducible)" loading to be considered appropriately.

The tributary area of one-way slabs is limited by section 1607.9.1.1.