Garage Conversions: Altadena vs Santa Monica
How do garage conversions rules compare between Altadena, CA and Santa Monica, CA?
Altadena and Santa Monica have similar restriction levels.
Altadena, CA
Los Angeles County
Garage conversions to ADUs in unincorporated Altadena are governed by LA County Code Title 22 §22.140.640 and California Government Code §65852.2. No replacement parking is required when an existing garage is converted, and existing setbacks are grandfathered. Properties in Very High Fire Hazard Severity Zones also trigger Chapter 7A wildland-urban interface standards.
View full Altadena rules →Santa Monica, CA
Los Angeles County
Santa Monica allows garage conversions to ADUs under SMMC §9.31.025. Replaced parking spaces do not need to be provided. Conversions of existing structures are exempt from setback requirements.
View full Santa Monica rules →Key Facts Comparison
| Fact | Altadena | Santa Monica |
|---|---|---|
| Governing Code | LA County Code §22.140.640 | - |
| Replacement Parking | Not required | Not required |
| Existing Setbacks | Grandfathered | - |
| Fire-Zone Construction | Chapter 7A in WUI hillside | - |
| Permit Required | Yes — LA County building | - |
| Code Section | - | SMMC §9.31.025 |
| Setback Exemption | - | Existing structures exempt |
| JADU in Garage | - | Allowed (attached garage) |
| Transit Parking Exempt | - | Within 1/2 mile of transit |
Highlighted rows indicate differences between cities.
Altadena FAQ
Do I need replacement parking if I convert my Altadena garage to an ADU?
No. Cal. Gov Code §65852.2 and LA County Code §22.140.640 prohibit the county from requiring replacement parking when a garage is converted to an ADU.
Are fire-resistant materials required for an Altadena garage conversion?
Yes, where the property is in a Very High Fire Hazard Severity Zone. Chapter 7A of the California Building Code requires ignition-resistant siding, eaves, vents, windows, and roofing in Altadena's hillside WUI areas.
Who handles the Altadena garage conversion permit?
LA County Public Works (Building & Safety) issues the building permit and LA County Regional Planning handles the ministerial ADU planning review under §22.140.640.
Santa Monica FAQ
Can I convert my garage into living space in Santa Monica?
Santa Monica allows garage conversions to ADUs under SMMC §9.31.025. Replaced parking spaces do not need to be provided. Conversions of existing structures are exempt from setback requirements.
What permits do I need for a garage conversion in Santa Monica?
Code Section: SMMC §9.31.025. Replacement Parking: Not required. Setback Exemption: Existing structures exempt. JADU in Garage: Allowed (attached garage).
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