A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Fillmore, CA
An ADU in Fillmore, CA costs somewhere between $145,000 and $320,000 for a detached unit, and $90,000 to $180,000 for a garage conversion. Those are honest numbers, not teaser bids. Fielding ADU Builders handles the whole job: plans, permits, foundation, framing, trades, and final inspection, with a written price before any work starts. Fillmore’s mix of older post-war homes and newer subdivisions means every lot has its own set of constraints, and we work through them without changing the number you approved. Call (361) 315-4177 when you’re ready for a real quote.
Why Fillmore Homes Are Different
Fillmore sits against the Santa Clara River and the flank of the Topatopa range, which means two things for ADU work: heat and drainage. Summer temperatures in the 90s and 100s make insulation and roof venting a real performance question, not a line item to skip. And the slope of many lots north of Highway 126 affects how we handle grading, retaining, and foundation drainage. We build ADUs in Fillmore with high-heat roofing materials, proper attic airflow, and setback-aware placement that accounts for the terrain.
Housing stock runs from 1940s bungalows near downtown to mid-century ranchers and 1990s-2000s developments on the east side. Older Fillmore lots are often generous in width but shallow in depth, which changes ADU placement geometry. Utility lines are sometimes overhead, sometimes underground, sometimes both on the same street. The city’s planning staff is practical, but Fillmore does enforce its accessory dwelling unit standards: setback minimums, height limits, lot coverage, and fire-safety requirements for units near wildland-adjacent parcels. We pull permits on every job and schedule inspections ourselves. It is the only way we know to finish clean.
Our Main Fillmore Services
Homeowners in Fillmore call us most often for three projects. Each has its own page with pricing, scope, and local detail. Here is the short version.
Room Addition Contractor in Fillmore
A room addition in Fillmore means expanding the footprint of a home that was probably built before anyone thought about a second bathroom or a dedicated laundry room. We frame, roof, insulate, and finish additions that match the existing lines rather than look bolted on. Older homes in Fillmore sometimes carry non-conforming setbacks, which means the city may require a variance (written permission to build closer to the property line than the standard rule allows). We handle that paperwork. See what a room addition involves and what it costs: Room Addition Contractor in Fillmore.
Garage Conversion Contractor in Fillmore
Most Fillmore garages from the 1950s and 60s were built as car storage, not living space: slab on grade, no insulation, single-circuit wiring, and enough headroom to hang a bike. Converting one into a bedroom, studio, or in-law suite means raising the floor system or pouring a new slab with a moisture barrier, running new electrical, insulating to current code, and adding proper egress windows. We do that work by the book, with permits pulled and inspections passed. Pricing and process are here: Garage Conversion Contractor in Fillmore.
ADU Builders in Fillmore
A backyard ADU in Fillmore can be stick-built on site or delivered as a prefab module. We work both ways, depending on lot access, budget, and what the homeowner wants out of the unit. A prefab ADU from Cover or Dvele can go from foundation to move-in faster than conventional framing, but the site still needs setbacks, a foundation, utilities, and the same inspections. A stick-built unit gives you more layout freedom. Either way, the price goes in writing before we start. Details: ADU Builders in Fillmore.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
- 2
You get an upfront price rangeHonest numbers before anyone is dispatched.
- 3
A background-checked tech heads outLicensed & insured, dispatched right away.
- 4
You approve before work beginsNothing starts until you say go.
Brands We Service in Fillmore
We work with prefab and modular ADU platforms including Cover, Dvele, and Boxabl, and we also build conventional ADUs using James Hardie siding. Parts for service calls are stocked locally or ordered within one business day, so a warranty follow-up does not put your project on hold. See the full list on our brands page.
Pricing for ADU Company in Fillmore, CA
| Service | Typical range in Fillmore |
|---|---|
| Detached ADU, stick-built | $145,000 – $320,000 |
| Garage conversion to ADU | $90,000 – $180,000 |
| Room addition, primary suite | $80,000 – $150,000 |
| Kitchen extension | $60,000 – $120,000 |
| Bathroom addition | $35,000 – $80,000 |
| Prefab ADU (Cover, Dvele, Boxabl) | $180,000 – $350,000 |
| Foundation and site work | $15,000 – $45,000 |
| ADU permit and plan set | $8,000 – $20,000 |
What pushes a Fillmore ADU to the top of that range: sloping lots that need retaining, overhead utility work, fire-hardening requirements on wildland-adjacent parcels, and custom finishes. What does not push the price up: change orders. We write the number down before any work starts, and that is the number on the final invoice. That rule is part of The Garrison Standard, and it is not negotiable.
Neighborhoods We Serve in Fillmore
We work across Fillmore, from the older blocks near downtown to the newer subdivisions east of Central Avenue and the properties that climb toward the foothills north of the river. Crews stage locally, so we are on site quickly for inspections and walk-throughs without a scheduling maze.
- Downtown Fillmore, including the blocks near Central Avenue and Main Street
- East Fillmore, including the subdivisions around Riverway and El Dorado
- North Fillmore, including properties along Goodenough Road and the foothill side of Highway 126
- West Fillmore, including streets near the Santa Clara River corridor
- Unincorporated areas just outside Fillmore city limits, including parcels off Guiberson Road
Service Area – Cities Near Fillmore
Our crews serve Fillmore and the surrounding communities in Ventura County. If you are in a neighboring city, the same written-price and one-year guarantee applies. We cover Moorpark, CA, Santa Paula, CA, Somis, CA, and Simi Valley, CA. Each city has its own permit office and its own quirks, and we work within both.
Serving Fillmore, CA - Our Local Coverage Area
We’re based in the Fillmore area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs About ADU Company in Fillmore
Permit review in Fillmore typically runs four to eight weeks depending on plan complexity and current workload at the building counter. We submit complete plan sets with the first application to avoid resubmit delays. Site work usually begins two to three weeks after permit issuance, once materials are staged and crews are scheduled. Call (361) 315-4177 for a current timeline based on your lot.
Yes. We pull all city permits, schedule every inspection, and handle the paperwork for setback variances when a lot requires one. If your HOA has design review, we provide the plans and documentation they ask for. The approval process is not free, and we list those fees in the written price before you sign anything.
No. The Garrison Standard requires a written price before any work begins, and the number you approve is the number on the final invoice. If you change the scope mid-project, we write a new change order with a new price before that work starts. Otherwise, the price holds. Call (361) 315-4177 to schedule a free estimate for your Fillmore property.
What happens when you call
- 1A real person answersNo phone trees - talk to a local adu pro.
- 2You get an upfront price rangeHonest numbers before anyone is dispatched. No surprises.
- 3We come out and measureLicensed & insured, at a time that suits you - the visit and the quote are both free.
- 4You get the price in writingLine-itemed, yours to keep, and nothing starts until you say go.
What Fillmore Customers Say
"Honest feedback on what the lot could fit. Told me up front what would fit on the lot and what the setbacks would allow."
- Rita C."Clear price breakdown. Change orders were all in writing."
- Hal P."Solid job. Cabinet delivery was a week behind but they worked around it."
- Ben G.
