A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Brentwood, CA
Fielding ADU Builders handles ADU construction, garage conversions, and room additions in Brentwood, CA. The city’s growing inventory of larger-lot homes makes detached ADUs a practical option here, while older neighborhoods closer to downtown often lean toward garage conversions. We put the price in writing before any work starts, and every project is covered by a written one-year guarantee. Call (361) 315-4177 for a free estimate.
Why Brentwood Homes Are Different
Brentwood sits at the eastern edge of Contra Costa County, where summer temperatures regularly climb past 100 degrees. That heat drives two ADU decisions: insulation packages and cooling. A detached unit without a mini-split or adequate attic insulation becomes unusable in July and August, so we plan HVAC capacity into the budget from the first walkthrough rather than treating it as an add-on later.
Lot shapes matter here more than in neighboring cities. Much of Brentwood’s post-2000 housing stock was built on larger suburban parcels, which gives homeowners room for a detached unit behind the primary house. But many of those same parcels came with HOA covenants written before ADU laws changed. We check the HOA’s recorded CC&Rs before quoting, so you know early whether a detached structure is feasible or whether a garage conversion is the cleaner path. Older pockets of town, particularly near Downtown Brentwood, have smaller lots and tighter side-yard setbacks, which often pushes designs toward attached units or conversions rather than freestanding buildings.
Our Main Brentwood Services
Most Brentwood homeowners call us about one of three projects: adding square footage to the main house, converting an existing garage, or building a separate ADU from the ground up. Each has its own page here.
Room Addition Contractor in Brentwood
A room addition in Brentwood means extending the footprint of the house you already live in, and the city’s larger foundation lots usually allow room to do it without eating the whole backyard. Heat is the consistent factor: a west-facing addition without proper glazing or insulation turns into a hot box by mid-afternoon. We frame, roof, insulate, and finish the addition as a sealed extension of the existing envelope, not a tacked-on afterthought. Full details are on the Room Addition Contractor in Brentwood page.
Garage Conversion Contractor in Brentwood
Garage conversions in Brentwood are often the most cost-effective way to add a rental unit or a long-term guest suite without changing the home’s footprint. The main wrinkle here is the existing slab: many Brentwood garages were poured as non-conditioned space, which means the concrete may need leveling and a moisture barrier before flooring goes down. We also replace the old garage door opening with a proper insulated wall and windows. See the Garage Conversion Contractor in Brentwood page for scope and pricing.
ADU Builders in Brentwood
Detached ADUs are common in Brentwood because large side and rear yards make them physically possible. Site work drives the schedule: establishing power from the main panel, running water and sewer lines across the yard, and grading the pad. We build conventional stick-frame units and also work with prefab manufacturers whose panels ship directly to Brentwood sites. The ADU Builders in Brentwood page covers build methods, timelines, and what to expect at permit review.
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 Brentwood
We build with conventional framing and also work with modular systems from Cover and Boxabl. When a client wants a prefab route, we coordinate the factory order, site prep, and local assembly. For panel-built units, Dvele components ship flat and go up faster than stick framing. See our brands for the full list.
Pricing for ADU Company in Brentwood, CA
| Service | Typical range in Brentwood |
|---|---|
| Detached ADU (prefab, turnkey) | $180,000 – $350,000 |
| Detached ADU (conventional build) | $250,000 – $450,000 |
| Garage conversion (attached) | $85,000 – $150,000 |
| Garage conversion (detached) | $70,000 – $120,000 |
| Junior ADU (interior conversion) | $60,000 – $110,000 |
| Primary suite addition | $90,000 – $180,000 |
| Second-story addition (per sq ft) | $250 – $450 per sq ft |
| Kitchen expansion | $60,000 – $130,000 |
| Foundation and slab work (per sq ft) | $12 – $22 per sq ft |
| Permit fees and city charges | Varies by scope; quoted before start |
Brentwood prices run higher on sites that need long utility trenching from the street, panel upgrades, or custom foundation work on sloped rear yards. Every estimate we give is a fixed written price, so the number you approve is the number on the final invoice.
Neighborhoods We Serve in Brentwood
We work across Brentwood from the older downtown grid to the newer subdivisions on the east side of the city. Response time for an initial site visit is typically within a few business days, and we schedule the walkthrough around your availability.
- Downtown Brentwood
- Garrett Park
- Summerset
- Deer Ridge
- Apple Hill
Service Area – Cities Near Brentwood
Our Brentwood crews also cover nearby communities throughout the region. If you’re in Ventura, CA, Ojai, CA, Oak View, CA, or Santa Paula, CA, we can schedule a site visit and quote your project under the same written-price policy.
Serving Brentwood, CA - Our Local Coverage Area
We’re based in the Brentwood 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 Brentwood
Yes. We prepare the plans, submit the permit application to the City of Brentwood, respond to plan-check comments, and pull the permit once approved. Permit fees are itemized on your written quote before work begins, not billed as a surprise later. Call (361) 315-4177 and we’ll walk through what your specific project triggers.
Brentwood’s summer heat means insulation and cooling are part of the plan from day one, not an upgrade. We size the HVAC for the unit’s square footage and orientation, and we spec windows with the sun exposure in mind. A unit facing west needs different glazing than one tucked under a north-side tree line.
No. The price we hand you before any work starts is a fixed written number. Change orders only occur if you ask to change the scope. We don’t move the price at the door or send a closing invoice that doesn’t match the estimate. Call (361) 315-4177 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 Brentwood Customers Say
"Room addition over the back patio. Framing is square, windows are tight, and the roofline matches."
- Danny L."Foundation and slab poured on schedule. Crew kept the yard orderly."
- Marian J."Garage conversion with a new bath and kitchenette. Permit was handled by them. Inspection passed first time."
- Sheila B.
