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.

Can I build a full-size 1,200 sqft ADU in Manhattan Beach?

MBMC §10.24 caps detached ADUs below state max in some lot sizes. We size the unit against the local ordinance during the feasibility walk.

Do I need a Coastal Development Permit in Hermosa?

Most of Hermosa Beach sits inside the Coastal Zone. A CDP is typically required unless the project qualifies for a categorical exclusion.

South Bay 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.

South Bay permits hinge on which beach city you're in. Manhattan, Hermosa, and Redondo each enforce a local ADU ordinance that's stricter than LA city's, capping detached unit size and adding parking rules in some sub-areas. Coastal Zone status and Palos Verdes geotech are the biggest schedule variables.

South Bay 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.

South Bay permit clock

8–14 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.

Manhattan Beach: ADU ordinance MBMC §10.24 — local design review for street-facing facades.
Hermosa Beach: tight side-yard setbacks on legacy walk-street lots.
Coastal Zone parcels (most of MB / HB) require a Coastal Development Permit.
Palos Verdes Peninsula: Portuguese Bend Landslide Complex overlays — geotech is mandatory, not optional.

What moves the South Bay number.

Highest detached cost in our service area — small lots, walk-street access, dump fees.
Coastal Development Permit consultant + biology costs commonly $20–60k on MB / HB lots.
Palos Verdes geotech (landslide complex) can add $35–100k in foundation engineering.
Local design review in Manhattan Beach often pushes architectural fees 25–40% higher.

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.
Can I build a full-size 1,200 sqft ADU in Manhattan Beach?: MBMC §10.24 caps detached ADUs below state max in some lot sizes. We size the unit against the local ordinance during the feasibility walk.
Do I need a Coastal Development Permit in Hermosa?: Most of Hermosa Beach sits inside the Coastal Zone. A CDP is typically required unless the project qualifies for a categorical exclusion.

More we build in South Bay.

Home Additions in nearby LA areas.

Got a South Bay project in mind?

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

Start a South Bay project →