Side Wall Plane Break

The side wall plane break is a requirement under Ordinance 184,802 (the Baseline Mansionization Ordinance) that any side wall in an R1 zone exceeding fourteen feet in height and forty-five feet or more in length must be broken with an offset. The offset must be at least five feet deep, beyond the required side yard setback, for at least ten feet of the wall’s length.

The rule applies citywide in the R1, R1V, R1F, R1R, RS, RE, and RA zones, except in designated Hillside Areas. In Hillside Areas, an equivalent rule with the same dimensions applies under the Baseline Hillside Ordinance, codified in LAMC 12.21C10 and detailed in Table 12.21C10-1.

The intent of the rule is to break up long, tall, undifferentiated side walls that would otherwise overshadow neighboring properties. The five-foot recess can take any form: a master bath bump-in, a closet recess, a balcony, a window seat alcove. What matters to plan check is the dimension and the length, not what fills the recess.

Plan checkers measure the side wall on each elevation. If the height exceeds fourteen feet at any point and the length exceeds forty-five feet anywhere on that elevation, the offset is required. Walls that almost reach the threshold but stop just short are flagged for verification: dimensions on the elevation drawing must show the wall length and height clearly.

The rule catches second-story additions over an existing one-story house most often. The first floor was built before the ordinance and may have a wall longer than forty-five feet. Adding a second floor to that wall, with standard floor-to-floor heights, almost always pushes the wall over fourteen feet tall. The addition needs to plan for the offset.

A common design failure: the original schematic plans do not include the offset, the plans go to plan check, the correction sheet flags the rule, and the project is sent back for redesign. Three weeks of rework is typical. The fix is to model the offset at concept, not after submittal.

Sources: City of Los Angeles Ordinance 184,802 (Baseline Mansionization Ordinance); LAMC Section 12.08C.2(a); Table 12.21C10-1; City of Los Angeles Department of Building & Safety, Plan Check Correction Sheets PC/STR/Corr.Lst.106A and PC/STR/Corr.Lst.107A.