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South Bay accessory dwelling unit by DECOMA Industries

Residential

Accessory Dwelling Units (ADU)

Detached, attached, garage-conversion, and junior ADUs across the South Bay — fully permitted under California state law, design through certificate of occupancy.

Why adu construction

An ADU is the cheapest square footage you can legally build on your lot — and the rules in 2026 are more permissive than most homeowners realize.

California has spent the last six years systematically removing the barriers that used to make ADUs hard. Owner-occupancy requirements: repealed. Parking-replacement requirements: gutted. Local-government approval discretion: heavily restricted. The result is that on almost any single-family lot in the South Bay, you can permit and build at least one detached ADU up to 1,200 square feet — ministerially, by-right, without going to a hearing.

What hasn't changed is the work itself. ADUs are real construction. Foundation, framing, plumbing, electrical, fire separation from the main house, sewer capacity, water meter sizing, electrical panel upgrades, weatherproof envelope, and finishes — all permitted, all inspected, all under code. The shortcut articles online that promise "ADU in 90 days from a shed kit" leave out the parts that go wrong.

DECOMA permits and builds ADUs across every South Bay city we serve: Manhattan Beach, Torrance, Redondo Beach, Palos Verdes Estates, Hermosa Beach, El Segundo, Rancho Palos Verdes, Harbor City, San Pedro, and the City of LA. Each city has its own plan-check quirks — Manhattan Beach's height calculation, Torrance's lot-coverage math, Palos Verdes' Art Jury triggers — and we've run them all multiple times.

Garage conversion, attached, detached, or junior ADU — the right answer depends on your lot, your budget, your goal (rental income, multi-generational housing, workspace), and how long you can wait. Start with a free 30-minute consultation: we walk the lot, tell you what's allowed, lay out the three or four ADU paths your lot actually supports, and give you an honest range on each.

Start with a free consultation → — or read our recent blog posts on ADU permits in Manhattan Beach and Palos Verdes Estates.

Written by John Notaro, President & CEO, DECOMA Industries — CSLB A/B #375508, California Real Estate Broker.

What you get

Everything we deliver.

  • 01

    Feasibility & lot analysis

    Setback math, lot-coverage check, sewer-vs-septic, electrical service capacity, easements, and grade. Done in week one so we know what kind of ADU your lot will actually hold before we start design.

  • 02

    Design & plans

    Schematic and construction documents for detached, attached, garage-conversion, or junior ADU. Drawn to your specific city's plan-check standards — Manhattan Beach, Torrance, Redondo, Palos Verdes Estates, Hermosa, El Segundo each have their own conventions.

  • 03

    Permits & state-law positioning

    Permit submittal positioned to use SB 9, SB 13, AB 2533, AB 1033, or AB 670 where they help — ministerial approval, height bonuses, parking exemptions, sale-to-third-party rights. We pick the right statute, you get the permit.

  • 04

    Utilities & service upgrades

    Sewer or septic capacity check, water meter sizing, electrical panel and service upsizing, gas line extension, separate-metering where required. Coordinated with the existing house's systems so nothing gets oversubscribed.

  • 05

    Construction

    Foundation, frame, weather-in, MEP rough, drywall, finishes, and exterior cladding. Self-performed structural and framing under our Class A engineering license. Typical on-site duration 5–9 months depending on size and type.

  • 06

    Final & certificate of occupancy

    Final inspections, gas and electric meter activation (if separate), certificate of occupancy, and a warranty walk. We'll connect you with a property manager if you're renting it out.

How we run it

Scope to sign-off.

  1. 01

    Lot walk & feasibility

    On-site visit to see the lot, the existing house, and the access route for construction. We pull zoning, setback rules, and any HOA restrictions before we leave. About 90 minutes on-site, results within a week.

  2. 02

    Design path selection

    Detached, attached, garage conversion, or JADU — we pick the path based on your goal (rental income vs. multi-generational housing vs. workspace) and your lot constraints. Each path has different cost, schedule, and permit implications.

  3. 03

    Plans & permit submittal

    Construction documents drawn to your city's plan-check standards. Permit cycle is typically 8–16 weeks in South Bay cities (ministerial ADU pathways are faster than discretionary). We handle the corrections rounds with the city.

  4. 04

    Construction

    Demo (for garage conversion), foundation, frame, weather-in, MEP rough, drywall, finishes, exterior cladding, landscape integration. 5–9 months on-site for most ADUs.

  5. 05

    Certificate of occupancy & lease-up

    Final inspections, meter activation, CO, and walk-through. If you're renting, we hand off to a property manager (in-house or yours) with as-built drawings and a maintenance plan.

Why DECOMA

One license, three disciplines, forty years.

Family-run South Bay general contractor since 1978. We design, build, and manage — under one license — so the team you start with is the team that hands you keys and the team that answers the phone when something needs fixing in year ten.

Years building
48+
Projects delivered
3,000+
Repeat clients
300+
CSLB Class
A/B

FAQ

Common questions.

What size ADU can I build on my lot?
California state law allows at least one detached ADU up to 1,200 sq ft on any single-family lot statewide — most South Bay cities follow that minimum. JADUs (junior ADUs) inside the existing house are capped at 500 sq ft. Garage conversions are limited to the existing footprint. Your specific lot may allow more under SB 9 (lot split) or local zoning. We measure on the walk-through.
Which is better — detached, attached, garage conversion, or junior ADU?
Depends on your goal. Detached gives the most rental privacy and the highest resale value, but costs the most and takes the longest. Garage conversion is fastest and cheapest but you lose covered parking and you're constrained to the existing footprint. Attached is in the middle. Junior ADU is best if you want to keep the unit family-only (often used for aging parents or adult children). We walk through the trade-offs on the call.
How long does a South Bay ADU take?
Garage conversion: 4–6 months total (1–2 month permit, 3–4 month build). Detached new construction: 10–14 months total (3–4 month design+permit, 7–10 month build). Add 2–4 months in cities with discretionary review (Palos Verdes Estates Art Jury, certain HOA review). Manhattan Beach and Torrance ministerial reviews are typically the fastest.
Do I have to live in the main house if I build an ADU?
California state law (AB 1033) lets you sell the ADU separately from the main house in cities that have opted in — increasingly common in 2026. If your city hasn't opted in, you don't have to live in either unit (the owner-occupancy requirement was repealed statewide). You can rent both. We'll tell you on the call what your specific city allows.
Will the ADU affect my property taxes?
Only the ADU's assessed value is added to your tax basis — the existing house is not reassessed. The county adds the cost of construction (roughly) as a supplemental assessment for the ADU only. The rest of your property keeps its Prop 13 basis. Your CPA can model the specific dollar impact.
Can DECOMA also manage the ADU after it's built?
Yes — our property management arm handles ADUs, multifamily, and commercial throughout the South Bay. The advantage is the manager comes in with the as-built drawings, the warranty docs, and the build team's notes from day one. Or we can hand off to your existing property manager.

Service areas

Adu construction across the South Bay.

Born in Harbor City, working across LA County since 1978. Same crew, same license number, same shop at 25941 Frampton Ave, Harbor City.

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One business day for a scope, timeline, and budget range. CSLB #375508 A/B.

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