ADU Construction · Lafayette, CA · CSLB #580756
ADU Construction in Lafayette, CA — Every Type, Every Site Condition
An accessory dwelling unit (ADU) is a complete, self-contained second home on the same lot as your primary residence — its own kitchen, bathroom, and entrance. Nearly every residential lot in Lafayette can add one, and many can add more than one. We assess your site, pull the Contra Costa County permits, and build it — detached, garage conversion, or JADU — with one 30-person in-house crew under a single contract.
What It Involves
What Full-Scope ADU Construction in Lafayette Actually Involves
Building a complete, permitted second dwelling unit on your existing lot — detached, attached, garage conversion, or a junior ADU carved out inside your home. Under California law, every Lafayette property is guaranteed at least one ADU of up to 800 square feet, and detached units are commonly approved up to 1,200 square feet where the site and local standards allow.
An ADU is a self-contained living space with its own entrance, kitchen, and bathroom. In Lafayette, every ADU runs through the Contra Costa County building department, and the 2026 state rules are the most homeowner-friendly they have ever been: a 16-foot height baseline for detached units (18 feet near major transit), 4-foot side and rear setbacks, a 60-day approval clock on complete applications, and no impact fees on units 750 square feet or smaller.
37 Years on These Lots
Lafayette ADU Construction, Built From Home Base
Rhino Builders has built in Contra Costa County for 37 years — and Lafayette is home base, two miles from most central neighborhoods.
- Two miles from the job site — crews reach Reliez Valley, Burton Valley & Happy Valley with no staging delays, so daily supervision keeps the build sequenced.
- Fire Hazard Severity Zones — every parcel checked against the CAL FIRE map before any material is specified.
- Hillside soils & setbacks — expansive clay and irregular setback envelopes we navigate every week.
From the Ground Up
Every Lafayette ADU starts with a site assessment — before a floor plan is drawn or a permit is filed.
I’m Shay Zilber, CEO of Rhino Builders, and I’ve led Bay Area construction for over 20 years. The most expensive problems in ADU construction are the ones discovered after the design phase.
A homeowner in Burton Valley had confirmed zoning approval and picked a floor plan before we walked the backyard together. The first pass revealed a three-foot grade change, a drainage path through the only viable placement zone, and a High Fire Hazard Severity Zone designation that changed the material spec entirely.
We assess slope, soil, utilities, and fire zone before any design begins — so the permit package is built around the lot that exists. That’s how a project reaches Certificate of Occupancy without revision cycles.
Shay Zilber
CEO, Rhino Builders · 20+ years leading Bay Area construction
No Budget Surprises
All Documented Costs Confirmed Before Your Contract Is Signed
Site prep — grading, drainage, retaining walls, utility connections — can shift an ADU budget significantly. Before a contract is signed, we document each site-specific input as its own line item.
- Utility connection — priced by lot position and service capacity, in your project picture before you commit.
- Geotechnical assessment — soils report priced up front if your slope triggers the county requirement.
- Fire-zone materials — WUI-compliant specs priced before the contract, never discovered mid-build.
A permit package with missing documentation draws a correction letter from the building department. Documenting everything correctly on the first submission avoids that entirely — full detail on our Lafayette Building Permits resource page.
Assessment to Occupancy
How We Move an ADU From First Walk to Move-In
Every Lafayette ADU runs through the same five phases, under one license and one contract.
01
Lot Conditions First
Slope, soil, fire zone, and utility stubs are recorded before design begins.
02
Lot-Specific Floor Plan
Studio, one-bed, or two-bed — based on what your setback envelope and coverage allow.
03
Complete Permit Package
Drawings, engineering, Title 24, and site docs built to clear plan check on the first round — the City must approve or deny a complete application within 60 days.
04
Single-Team Construction
Our 30-person crew handles every trade — nothing handed to the homeowner.
05
Inspections to C of O
We manage every inspection through to certificate of occupancy.
One Sequence, One Team
Permits, Engineering & Construction Managed as a Single Process
The permit process in Lafayette runs through Contra Costa County — with specific requirements general ADU guidance doesn’t cover. We’ve filed here for decades.
- Site assessment & documentation — fire-zone overlay and soils reports go into the package before submission, not after.
- Package preparation & submission — assembled against Contra Costa County's own submittal checklist.
- Construction & final inspection — a sequenced trade schedule, each phase signed off before the next.
37 Years in the Field
Permitted ADU builds across Contra Costa County — assessed on the ground, approved on the first submission.
Every Type, Every Lot
Types of ADU Construction We Complete Across Lafayette
Each ADU type follows a different structural and permitting path — the right choice depends on your lot and goals. Most Lafayette single-family lots can combine more than one, commonly a standard ADU plus a JADU inside the main home. For multi-unit properties or an SB 9 lot split, see our multi-family ADU construction page.
A freestanding unit fully separate from the main home — up to 1,200 sq ft where the site allows, and the strongest option for rental income and resale.
Up to 500 sq ft created inside your existing home — the lowest-cost path, and as of 2026 no owner-occupancy requirement when it has its own bathroom.
Converting an existing garage into permitted living space — fire separation, ceiling height, and panel upgrades assessed first. Often the fastest, lowest-cost ADU.
Ready to Talk About Your ADU?
The first step is a conversation about your lot — not a commitment. Tell us where it is, whether you’re thinking attached, detached, or garage conversion, and what you know about the site.
3685 Mount Diablo Blvd #161, Lafayette, CA 94549
Good to Know
Questions Lafayette Homeowners Ask About ADU Construction
Most Lafayette ADU projects run 12–18 months from first site assessment through certificate of occupancy — covering assessment, design, permit review through Contra Costa County (typically 4–8 weeks for a complete first-round submission), and construction.
Slope grade, soil bearing, utility stub locations, and your parcel’s Fire Hazard Severity Zone — all assessed before any floor plan is drawn.
Rhino Builders prepares and files the complete permit package with the Contra Costa County Building Department. Homeowners don’t manage submissions, corrections, or inspections.
Lot slope and utility-connection complexity are the biggest site-driven variables; unit size and finish level are the largest design-driven ones — all documented as line items before the contract.
Yes — the slope determines what engineering is required first: typically a geotechnical report, grading plan, and retaining-wall engineering, all identified during the site assessment.
A detached ADU is freestanding; an attached ADU shares a wall and is structurally integrated. They differ in foundation and utility routing, but both go through the same Contra Costa County permit process.
Most single-family lots can add more than one unit — commonly one standard ADU plus one JADU, and in many cases an additional conversion unit. There is no minimum lot size for the state-guaranteed 800-square-foot ADU; slope, setbacks, and utility access matter more than raw lot size. We confirm the exact combination during your site assessment.
No. Only the new ADU is assessed and added to your tax bill — your main home’s existing assessed value is protected under Proposition 13. You’re taxed on the value the ADU adds, not on a reassessment of the entire property.