Garage Conversions: Altadena vs Carson
How do garage conversions rules compare between Altadena, CA and Carson, CA?
Carson has fewer restrictions than Altadena.
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 →Carson, CA
Los Angeles County
Garage conversions in Carson are governed primarily by California state ADU law (Gov. Code §65852.2), which preempts local bans and requires ministerial approval of conversion ADUs in existing garages.
View full Carson rules →Key Facts Comparison
| Fact | Altadena | Carson |
|---|---|---|
| Governing Code | LA County Code §22.140.640 | - |
| Replacement Parking | Not required | - |
| Existing Setbacks | Grandfathered | - |
| Fire-Zone Construction | Chapter 7A in WUI hillside | - |
| Permit Required | Yes — LA County building | - |
| State law | - | Gov. Code §65852.2 (ADU; re-numbered by SB 477, 2024) |
| Approval | - | Ministerial within 60 days; no discretionary review |
| Parking | - | No replacement parking required when garage was required parking |
| Lot standards | - | Conversion ADU exempt from FAR/coverage/min-lot-size |
| Permit portal | - | cityofcarsonca-energovweb.tylerhost.net |
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.
Carson FAQ
Can Carson make me replace parking when I convert my garage to an ADU?
No. Under Gov. Code §65852.2, the city cannot require replacement off-street parking when a garage converted to an ADU was previously used for required parking. State law preempts any local replacement-parking rule for ADU conversions.
How long does Carson have to approve a garage-conversion ADU?
State law requires ministerial approval within 60 days of a complete application. The city cannot impose discretionary review, hearings, or owner-occupancy requirements (the owner-occupancy moratorium was extended through 2025 by AB 671).
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