Related Entries
City of Los Angeles
Encroachment Plane
Code Reference
LAMC 12.08C.5(a)
Table 12.08C.5(b), (c), (d)
LADBS Form PC/STR/Corr.Lst.106A, Part III.B
Definition
The encroachment plane is an invisible inclined plane that slopes inward, at a forty-five-degree angle from the vertical, from the required front and side yard setbacks. It originates at a specified height above grade and rises at the angle until it intersects the height limit of the zone.
Buildings may not intersect the encroachment plane. The plane is the geometric expression of the city’s anti-mansionization intent: tall walls cannot sit hard against the property line. The closer to the property line a building is, the lower it must be at that point.
In the R1 zone, the encroachment plane originates twenty feet above grade. In other zones (R1V, R1F, R1R), the origin height varies and is set by Table 12.08C.5. The angle is always forty-five degrees, measured from existing or finished grade, whichever is lower.
What flags it in plan check
On every elevation drawing for an R1 zone project, the encroachment plane must be shown. A line at the required side or front yard setback, rising vertically to the origin height, then sloping inward at forty-five degrees. Any portion of the building — wall, parapet, projecting eave — that crosses the line is a violation.
Eaves and parapets get particular attention from plan checkers. The encroachment plane restriction does not apply to certain roof structures and equipment that are explicitly allowed to project beyond it under LAMC 12.21.1.B.3. Anything outside that allowed list and crossing the plane will trigger a correction.
On corner lots and lots with prevailing setbacks shorter than the zone default, the encroachment plane shifts inward with the setback. This is one of the more common sources of design rework: the building was designed assuming the zone default setback, the prevailing setback turned out to be tighter, the encroachment plane moved with it, and the upper floor no longer fits.
Connected Terms
Sources. Sources: LAMC Section 12.08C.5(a); Table 12.08C.5(b)(c)(d); City of Los Angeles Department of Building & Safety, Plan Check Correction Sheet PC/STR/Corr.Lst.106A.
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