LA Mansionization Rules — BMO and BHO (2026)
LA's Baseline Mansionization Ordinance caps how big you can build on a single-family lot. This guide covers the math: FAR limits, encroachment plane, front-yard setback, how a 6,000 sqft plan on a 7,500 sqft lot comes up short.
FAR (Floor Area Ratio) — the master limit
R1-1: typically 0.45 FAR. So a 7,500 sqft lot caps at 3,375 sqft of floor area.
R1-2: 0.40 FAR.
RA (Rural Agricultural): 0.35 FAR.
Bonus FAR available with Green Building features (+0.10) or affordable units (+0.20).
What counts toward FAR
All enclosed conditioned space — living areas, bedrooms, bathrooms, kitchens.
Garages generally count (up to a 400 sqft garage exemption on some parcels).
Basements below grade typically don't count (if finished below grade per code).
Attics typically don't count (unless habitable, in which case they do).
ADUs up to 800 sqft don't count toward primary FAR (state exemption).
Encroachment plane
Sloped 45-degree plane rising from side property lines — limits how tall you can build near the lot edge.
Designed to preserve neighbor daylight and reduce "wall effect."
Sculpts second-story additions away from the neighbors.
Front yard setback
Prevailing setback within 500 ft of your parcel on the same block face.
Catches homeowners off-guard when they plan a front-facing addition that protrudes past the block's established line.
BHO — Baseline Hillside Ordinance
Stricter limits for hillside parcels.
Slope-based FAR reduction: steeper slopes = lower allowed FAR.
Export quantity limits: how much soil you can haul off the site during grading.
Import limits: how much fill you can bring in.
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He wasn't the first to see them. Edmond Halley saw them in 1715 and barely noticed. Baily's contribution was clarity — describing exactly what was happening, in plain language, so vividly that the whole field of astronomy paid attention. The phenomenon is still called Baily's beads.
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