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 accessory dwelling unit (ADU) is a self-contained second home built on a lot you already own, with its own kitchen, bath, and entrance. In Fillmore, CA, ADU work usually falls into three buckets: a standalone backyard unit, a garage conversion, or an addition that extends the main house. This page is the place to understand how Fillmore lots, weather, and local rules shape the work before you dig into each service. Russ Delmar leads our Fillmore projects, and you can reach the team any time at (831) 230-7250.
Why Fillmore Homes Are Different
Fillmore sits in the Santa Clara River Valley, which means summer heat is real and drainage matters more than people expect. A detached ADU out here needs a foundation plan that handles dry, compacted clay soil that swells after winter rain. Homes in Fillmore run older than what you’ll find in newer Ventura County developments, especially north of Highway 126 and around Central Avenue, where many lots were platted generations ago. That changes how we run power, where the sewer lateral sits, and how much trenching a job needs.
Older Fillmore lots also tend to be wider than deep in the original grid, which matters when you’re placing a prefab unit from Cover or Dvele. We look at side setbacks, existing easements, and where the sun hits in July before we recommend a floor plan. Permits go through Ventura County, and Fillmore’s planning department reviews detached ADUs against lot-coverage rules that aren’t always obvious on paper. None of this is a problem, it’s just the local reality that shapes a good build.
Our Main Fillmore Services
Fillmore homeowners typically ask us about three paths to more space: extending the house they have, converting a garage they aren’t using for cars, or building a standalone ADU from the ground up. Each has its own page with local detail.
Home Addition Contractor in Fillmore
A home addition in Fillmore means working within the footprint and roofline of the existing house, which on many older Central Avenue properties requires matching framing methods that aren’t used anymore. We price the structural tie-in honestly because that’s where surprise costs usually hide. Summer heat also pushes additions toward better insulation than the original 1950s walls had, so we plan for that in the first estimate. Home Addition Contractor in Fillmore has the full breakdown.
Garage Conversion Contractor in Fillmore
Garage conversions are popular in Fillmore because so many detached garages sit at the back of the lot, already wired and already permitted as a structure. That said, Fillmore garages from the mid-century often have slab floors that were never intended for living space, so we check elevation and moisture before quoting. Converting usually costs less than a ground-up ADU and moves faster, which matters when you’re housing family. Garage Conversion Contractor in Fillmore covers specifics.
ADU Builders in Fillmore
A detached ADU in Fillmore is a standalone small home built from the foundation up, and it’s the most flexible way to add a rental, a guest house, or a quiet work space. Fillmore’s lot shapes and soil conditions make site prep the biggest variable, so we bring that cost into the first written price. We work regularly with prefab systems from Boxabl and Mighty Buildings when the schedule matters and the lot can take a crane or panel delivery. ADU Builders in Fillmore walks through the process.
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
The Kingswell family has always believed a lodge is a small house on a larger property, which is exactly what an ADU is. We service and build with Cover, Dvele, and Boxabl units in Fillmore, and we keep common trim, flashing, and touch-up materials on hand so small fixes don’t wait on a parts shipment. Our brands page explains which systems we recommend for which lots.
Pricing for ADU Company in Fillmore, CA
The numbers below are what we see across Fillmore right now, quoted as a range because no two lots or existing structures are the same. Every job still gets a specific written price before any work starts.
| Service | Typical range in Fillmore |
|---|---|
| Detached ADU (400 – 800 sq ft, site-built) | $180,000 – $340,000 |
| Detached ADU (prefab, 400 – 600 sq ft) | $150,000 – $260,000 |
| Garage conversion (attached, 300 – 500 sq ft) | $90,000 – $160,000 |
| Garage conversion (detached, 300 – 500 sq ft) | $110,000 – $190,000 |
| Home addition (300 – 600 sq ft) | $140,000 – $280,000 |
| Primary suite addition (250 – 400 sq ft) | $110,000 – $210,000 |
| Kitchen expansion (150 – 300 sq ft) | $80,000 – $160,000 |
| Permitting and plans (typical Fillmore project) | $8,000 – $20,000 |
| Site prep and foundation (flat vs. sloped lot) | $15,000 – $45,000 |
| Utility connections (water, sewer, power) | $10,000 – $28,000 |
In Fillmore, the biggest price swings come from soil conditions, how far the panel and sewer line sit from the build site, and whether the lot needs fill or retaining. That’s exactly why we don’t quote over the phone and why the written price we give you before work begins is the price you pay, no change orders at the door.
Neighborhoods We Serve in Fillmore
We work across the whole Fillmore area, from the older blocks near downtown up to the newer lots north of the 126. Crews typically reach any Fillmore address within a normal scheduling window, and we confirm the arrival window in writing before the day of the job.
- Central Avenue and the original grid
- Riverwalk and the neighborhoods near the Santa Clara River
- North Fillmore above Highway 126
- El Dorado and the mobile home community area
- The farm-adjacent lots east toward the orchards
Service Area – Cities Near Fillmore
Fillmore sits between the river valley and the hills, and our crews also cover the surrounding communities in the same scheduling area. If your property is in Santa Paula, CA, Moorpark, CA, Somis, CA, or Simi Valley, CA, the same written-price promise applies.
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
After you sign the written estimate, we typically schedule the first site visit within a week or two, then move into plans and permitting. Permit review times in Fillmore vary by project type and current county workload, but the timeline is put in writing at the start. Call (831) 230-7250 to get your specific schedule.
Yes. We prepare and submit the drawings and applications the county needs, and if your Fillmore neighborhood has an HOA, we supply the documents their review board asks for. You still own the communication with your HOA, but the paperwork burden sits with us where it belongs. Estimates include permitting costs as a line item.
The written price we give you before work begins is fixed unless you ask to change the scope, in which case the change is priced in writing before any extra work happens. That’s the Kingswell Guarantee and it applies on every Fillmore project, from a small garage conversion to a full detached ADU. Call (831) 230-7250 for a free estimate.
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
"Added a bedroom and bath for our growing family. Honest from day one about what was possible and what it would cost. Showed up when they said and the work has held up great."
- Troy Benavidez"Turned our detached garage into a little guest house. Clean crew, respectful of the neighbors, and no mystery charges at the end. Love how it turned out."
- Carmela Fontes"Converted our garage into a rental studio. The crew was respectful of the neighbors and kept the site clean. It's bringing in rent now and paid for itself faster than I expected."
- Grace Yoon
