Cost to install LA french drain?

$4K–$12K typical perimeter drain.

Basement waterproofing in LA?

$15K–$35K for a full interior-exterior system.

Do I need a Coastal Development Permit for a Westside ADU?

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.

Can I build an ADU in Santa Monica's R1?

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.

Westside Drainage & Waterproofing.

LA drainage — french drains, area drains, downspout extensions, sump pumps. Hillside homes get engineered solutions.

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.

Westside cost band — 2026

$4K – $35K

Surface french drain bottom; full basement system top.

Westside permit clock

8–12 weeks ministerial

3–7 days for typical drainage system.

Scope — start to keys.

Site assessment
Engineering if needed
Permit
Excavation + install
Backfill + test

What changes about the permit here.

City of LA parcels: LADBS ePlanLA portal, ministerial ADU review under LAMC §12.22-A,33.
Santa Monica parcels: SMMC §9.31.300 — locally streamlined, similar 60-day clock as state law.
Coastal Zone (Venice west of Lincoln, Marina Peninsula): Coastal Development Permit may be required.
Mello Act applies to demolition or replacement of existing residential units in the Coastal Zone.

What moves the Westside number.

Westside labor and dump fees price 8–12% above LA County median.
Coastal Zone parcels often add $15–40k in CDP consultant + biology survey costs.
Santa Monica seismic retrofit pairing on a duplex can add $35–80k tied to the ADU permit cycle.
Tight street parking (Venice, Mar Vista) drives crane / pump days higher than Valley jobs.

In short.

Cost to install LA french drain?: $4K–$12K typical perimeter drain.
Basement waterproofing in LA?: $15K–$35K for a full interior-exterior system.
Do I need a Coastal Development Permit for a Westside ADU?: 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.
Can I build an ADU in Santa Monica's R1?: 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.

More we build in Westside.

Drainage & Waterproofing in nearby LA areas.

Got a Westside project in mind?

Send us the address and we’ll pull Westside zoning, setbacks, and drainage & waterproofing feasibility before you spend on drawings.

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