ADU builders in San Fernando

San Fernando is its own 2.4-square-mile city inside the Valley — 1920s bungalows and Spanish cottages near downtown, postwar stuccos toward the edges, and multigenerational households on almost every block. It's also our home turf: Guillen Construction is based right here at the Mission Hills line, so a walkthrough usually happens within days.

ADUs & Garage Conversions · San Fernando

Why San Fernando homes bring this work to us

San Fernando runs its own ADU process — smaller counter, faster conversations — and its lots were made for this: alley garages behind 1920s bungalows and postwar homes with room in back. Most of what we build here is family housing: a permitted unit for parents or a newlywed kid, built so it can earn rent later.

We're based in Mission Hills, so San Fernando is home turf — walkthroughs usually happen within a couple of days.

Neighborhoods we work in

Maclay Avenue corridorLas Palmas Park areaDowntown San FernandoHuntington Estates sideO'Melveny neighborhood

ZIP codes: 91340 · Serving all of San Fernando and the surrounding San Fernando Valley.

What's included

ADUs we build in San Fernando

Detached new-build ADUs

A complete small home in your backyard — foundation, framing, systems, and finishes, up to 1,200 sq ft under state law.

Garage conversions

The fastest, most affordable path to a rentable unit: foundation checks, insulation, systems, and a finish that doesn't feel like a garage.

Attached ADUs & JADUs

Additions and junior units carved from existing space, with the required separate entrance and kitchen done to code.

Guest houses & casitas

Not every backyard building needs a full kitchen — we build casitas, studios, and offices to the same standard.

Site work & utilities

Trenching, sewer connections, panel upgrades, and meters — the part of ADU budgets everyone forgets. We price it up front.

Plans, engineering & permits

Architectural plans, structural engineering, Title 24, and city plan check — or we build from the plans you already have.

$100k–$180k
Typical garage conversion, turnkey
$250k–$400k+
Typical detached ADU, turnkey
$1,800–$2,800/mo
Typical SFV ADU rent today

Typical 2026 Los Angeles-area ranges including construction; plans, permits, and utility fees vary by city and site. Many owners see the unit pay for itself in 7–12 years of rent.

FAQ

Questions we hear a lot

Who handles building permits in San Fernando?

Permits here go through the City of San Fernando's own Community Development Department on First Street — a small, independent city hall we work with constantly, since our shop is minutes away. We prepare the plans, pull the permits, and meet the inspectors — you never stand in a city line.

What does an ADU cost in San Fernando?

Turnkey garage conversions typically run $100k–$180k and detached new-build ADUs $250k–$400k+ — San Fernando sits squarely in those ranges. Utilities and site conditions move the number, which is why we start with a free site check and give you a written, line-item price.

How fast can you get to San Fernando?

We're based in Mission Hills, so San Fernando is home turf — walkthroughs usually happen within a couple of days. Estimates are free and come back as a written, line-item scope — not a guess over the phone.

Also in San Fernando

Nearby city guides

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