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Westside Home Additions.

Adding space to an existing LA house is a different project than building from scratch — you are tying into 1920s framing, surveying the lot for setbacks, and protecting an occupied home through the build. We design additions that match the original house, hold the existing roofline, and pass LADBS structural review the first time.

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

$400 – $700 / sqft (first-story); $550 – $900 / sqft (second-story)

Foundation work, roof tie-in complexity, and how much of the existing house you have to touch drive the band.

Westside permit clock

8–12 weeks ministerial

Plan on 4–6 months for design + LADBS permit, then 5–8 months on-site for a 500–800 sqft addition.

Scope — start to keys.

  • Setback / FAR / hillside check before contracting
  • Architectural design that matches the existing house line
  • Structural tie-in — footings, framing, roof
  • Full MEP extension and panel upgrade if required
  • Finishes, exterior siding/stucco match, paint, landscape repair

What changes about the permit here.

  1. City of LA parcels: LADBS ePlanLA portal, ministerial ADU review under LAMC §12.22-A,33.
  2. Santa Monica parcels: SMMC §9.31.300 — locally streamlined, similar 60-day clock as state law.
  3. Coastal Zone (Venice west of Lincoln, Marina Peninsula): Coastal Development Permit may be required.
  4. 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.

How much does a home addition cost in Los Angeles?
First-story additions in LA typically run $400–$700/sqft installed. Second-story additions run $550–$900/sqft — they cost more because of the structural work to the floor below.
Can I add a second story to my LA house?
Usually yes, but the existing foundation and first-story framing have to support the load — we engineer the structural retrofit. Hillside Ordinance and view-protection rules can limit height.
Do I need to move out during a home addition?
Not usually. We sequence and dust-protect so the addition tie-in is the last phase. Most of our LA clients stay in the house the whole project.
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.

Home Additions in nearby LA areas.

Got a Westside project in mind?

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

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