California state law has opened the door for most Brentwood homeowners to add an Accessory Dwelling Unit (ADU) on their lot. This guide covers the rules, the design choices, and the build process.
State law vs local rules
California Government Code 65852.2 (the state ADU law) sets a floor: every single family lot can have at least one ADU plus one Junior ADU. Cities can add layers on top but cannot block ADUs entirely. Brentwood has its own ordinance that further shapes setbacks, height, and lot coverage.
Site feasibility
Before design, walk the lot for setbacks, sewer capacity, electrical service capacity, slope, and easement constraints. Detached new build ADUs need a footprint and yard space. Garage conversions reuse an existing structure. Junior ADUs sit inside the main house. Each path has its own cost basis and construction timeline.
Permits in Brentwood
ADU submittals are ministerial in California, meaning the city reviews them administratively without discretionary review. LADBS for building, LA City Planning for entitlements. typically completes plan check in 60 to 120 days. BMO reduced livable building allowance to 0.45 FAR and removed the prior 20 percent bonuses for certain architectural characteristics. BHO additionally caps grading, retaining wall height, and total floor area when slopes exceed defined thresholds. Garage conversions usually clear faster than detached new builds.
Construction window
Site clearance, foundation, framing, MEP rough, exterior dry in, interior finish, fixture install, final inspection. ADU builds in Brentwood typically run 4 to 7 months of construction. From signed design contract to final inspection most projects total 8 to 14 months.
ADU rules specific to Brentwood
State conforming via LADBS. Hillside parcels still pull BHO height and lot coverage caps.
How Paradigm Builders Can Help in Brentwood
Paradigm Builders runs design, permits, and construction across the full residential scope in Brentwood. Browse our service pages for what fits your project:
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