City of LA · field-data comparison
ADU cost · permits · timeline · which one wins
BHO (Baseline Hillside Ordinance) lots vs flatland Westside parcels — same city, very different soils reports, retaining, and access cost. We've seen the same square footage swing $150k between the two.
| Metric | Hills & Canyons | Westside |
|---|---|---|
Detached ADU ($/sqft) All-in installed, 2026 USD. | $550–$800 | $475–$625 |
Garage conversion ($/sqft) | $325–$475 | $275–$400 |
Ministerial permit clock End-to-end, including agency back-and-forth. | 12–18 wk | 8–12 wk |
Discretionary review | 22–36 wk | 16–28 wk |
Permit story
Hill parcels add the Baseline Hillside Ordinance, geotech, and (along the ridgeline) the Mulholland Scenic Parkway Specific Plan to every permit package. The ADU itself is still ministerial, but plan-check takes longer because the structural, grading, and haul-route sheets are heavier than a flat-lot project.
Full Hills & Canyons field notes →Permit story
Westside permits move quickly when the parcel is clearly inside the city of LA or Santa Monica grid — both jurisdictions run ministerial ADU review under state law. The variables are Coastal Zone status (anything west of Lincoln Blvd in Venice / Marina Peninsula), and whether a soft-story or seismic ordinance applies to the existing structure.
Full Westside field notes →Hills & Canyons
Westside
Hills & Canyons
Westside
The cheaper detached build, on paper, is Westside (top-end $625/sqft vs $800/sqft). The faster permit clock belongs to Westside (12 weeks vs 18 weeks ministerial). Those headlines flip once you factor in overlays, water-utility coordination, and design constraints — which is why we sketch the parcel before we ever quote a number.
Almost never. State ADU law overrides local FAR limits up to 800 sqft, and many hillside lots can fit a full 1,200 sqft attached ADU even under BHO.
Plan on $8–25k for the report itself. The downstream cost — caissons, retaining walls, deeper foundations — is where the real budget impact lives.
HCR (Hillside Construction Regulation) limits truck size and operating hours on hillside streets. We file the haul-route permit alongside the building permit, not after.
Only if the parcel is inside the Coastal Zone — generally west of Lincoln Blvd in Venice and the Marina Peninsula. Inland Westside parcels (most of Santa Monica, Brentwood, Mar Vista east of Lincoln) do not.
Yes. SMMC §9.31.300 mirrors state ADU law on R1, R2, and multifamily lots, with ministerial 60-day review once the submittal is complete.
If your existing building is on the LA or Santa Monica soft-story list, the city often requires the retrofit to be permitted alongside the ADU. We coordinate both packages to keep one inspection schedule.