Los Angeles vs Norwalk
How do anti-mansionization rules compare between Los Angeles, CA and Norwalk, CA?
Norwalk has fewer restrictions than Los Angeles.
Los Angeles, CA
Los Angeles County
The 2017 Baseline Mansionization Ordinance (LAMC §12.21.1, Ord. 187709) caps single-family residential floor-area-ratios between 0.40 and 0.50 of lot area, ending earlier bonuses and tightly limiting oversized homes in R1 hillside and flatland neighborhoods.
View full Los Angeles rules →Norwalk, CA
Los Angeles County
LA County has no countywide BMO like LA City, but Title 22 Chapter 22.110 sets hillside grading and bulk limits, and several Community Standards Districts cap floor area ratio in unincorporated communities like Altadena, La Crescenta-Montrose, and Topanga.
View full Norwalk rules →Key Facts Comparison
| Fact | Los Angeles | Norwalk |
|---|---|---|
| R1 base FAR | 0.45 of lot area | - |
| Hillside cap | Often 0.40 or lower | - |
| Effective date | March 17, 2017 | - |
| Ordinance number | 187709 | - |
| ADU treatment | Excluded from RFA | - |
| Hillside rules | - | Title 22.110.090 |
| Altadena CSD FAR cap | - | 0.45 floor area ratio |
| Reviewing agency | - | Department of Regional Planning |
| CSD count | - | Roughly 20 districts countywide |
| Grading authority | - | LACoDPW Building & Safety |
Highlighted rows indicate differences between cities.
Los Angeles FAQ
Does an attic count toward floor area?
Yes if interior height exceeds 7 feet. Habitable attics, lofts, and high-volume rooms over 14 feet are double-counted under the 2017 Baseline Mansionization Ordinance.
Are there exceptions in R1 Variation Zones?
Yes. R1V1 through R1V3 and 21 RFA Districts apply tighter caps, side-wall articulation, and front-facade rules. Check the Zoning Information map before designing additions.
Norwalk FAQ
Does LA County have a Baseline Mansionization Ordinance like LA City?
No. The county uses Community Standards Districts and hillside standards instead of a single BMO. Each CSD applies different FAR, height, and setback rules tailored to that unincorporated community.
How do I know which CSD covers my property?
Department of Regional Planning's Z-Net online parcel viewer shows applicable CSDs, hillside management areas, and zoning. Contact DRP before filing plans for additions in Altadena, Topanga, or other CSD areas.
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