A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Sunnyvale, CA
Fielding ADU Builders handles accessory dwelling units, garage conversions, and room additions across Sunnyvale. Sunnyvale jobs tend to move faster than most of Santa Clara County because the city publishes prescriptive ADU plans and pre-approved design options, but the older ranch homes that dominate the housing stock usually need panel upgrades and seismic shear-wall work before construction starts. That combination – quick permitting, older wiring, real earthquake requirements – is what shapes a Sunnyvale ADU budget. Call (669) 201-3984 for a written, line-item price before any work begins.
Why Sunnyvale Homes Are Different
Most of Sunnyvale is post-war single-family tract housing: 1950s-to-1970s ranch and split-level homes on 6,000 to 8,000 square foot lots. The rear yards are flat and unusually large for the Bay Area, which is why detached ADUs are feasible on a bigger share of lots here than in neighboring cities. The catch is inside the original house. A large number of these homes still run on 100-amp electrical panels, and adding an ADU means upgrading to 200 amps or more, plus running a new feeder to the rear unit. We price that work into the written estimate from day one.
The climate works in a homeowner’s favor: Sunnyvale’s Mediterranean pattern means an ADU needs a real heating system but rarely needs air conditioning, though many owners add a small A/C unit anyway because tenants expect it. The opposite pressure is seismic. Homes here sit within reach of the San Andreas and Calaveras faults, so Sunnyvale’s building department enforces foundation tie-down and shear-wall requirements even on small detached units. That adds a few thousand dollars to a build, and it is not optional. Anyone who tells you otherwise has not pulled a permit in this city.
Our Main Sunnyvale Services
Most Sunnyvale homeowners call us about one of three projects – adding a room, converting an existing garage, or building a detached ADU in the rear yard. Each one has its own Sunnyvale page with pricing and specifics, linked below.
Room Addition Contractor in Sunnyvale
A room addition in Sunnyvale usually means extending off the back of a ranch home, which keeps the front elevation intact and uses that deep rear yard. The work involves matching the original roofline, tying framing and shear walls to the existing structure, and bringing the new square footage up to current energy code – which often means added wall insulation the 1960s original never had. We price the full scope in writing before permits are pulled. See Room Addition Contractor in Sunnyvale for per-square-foot costs and timelines.
Garage Conversion Contractor in Sunnyvale
Garage conversions in Sunnyvale carry a specific local question: whether the city will accept the existing slab foundation or require seismic and moisture upgrades. Many 1950s-1970s slabs were poured without the rebar and vapor barriers the current code demands for living space, so some conversions need a new slab pour, not just framing and drywall. We inspect first, then price the conversion to match how the city will actually treat the structure. Full pricing is on the Garage Conversion Contractor in Sunnyvale page.
ADU Builders in Sunnyvale
Detached ADUs are the fastest-growing project type in Sunnyvale, and the city encourages them. The Sunnyvale Standard gives owners a set of prescriptive plans and pre-approved design options, which shortens plan review meaningfully compared to a fully custom submission. We work with both prefab platforms and conventional construction on these, and we handle the electrical panel, the permit set, and the final tie-in to the main house as one scope. Read ADU Builders in Sunnyvale for detached ADU ranges, including prefab and stick-built options.
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 Sunnyvale
We install and finish work from several ADU and construction platforms Sunnyvale homeowners already research, including Abodu, Plant Prefab, and Tuff Shed-style structures, plus conventional builds with James Hardie siding. When a platform requires certified installers, we coordinate directly with the manufacturer so the warranty stays intact. See our brands for the full list and what each platform suits in a Sunnyvale lot.
Pricing for ADU Company in Sunnyvale, CA
These are the ranges we write into Sunnyvale contracts for the most common scopes. Every figure assumes a permitted build; permit fees are separate and paid to the city.
| Service | Typical range in Sunnyvale |
|---|---|
| Detached ADU (prefab/modular) | $180,000 – $320,000 |
| Detached ADU (conventional build) | $250,000 – $450,000 |
| Garage conversion to ADU | $120,000 – $220,000 |
| Attached ADU (master-suite style) | $150,000 – $260,000 |
| Electrical panel upgrade (100A to 200A) | $4,000 – $8,000 |
| Foundation and shear-wall seismic retrofit | $12,000 – $30,000 |
| Plumbing rough-in for ADU | $8,000 – $22,000 |
| HVAC rough-in for ADU | $6,500 – $15,000 |
| Interior finish (drywall, paint, millwork) | $35 – $75 per sq ft |
| Exterior siding and trim | $12 – $28 per sq ft |
What pushes a Sunnyvale price up is usually the panel, the shear-wall scope, or a grading correction on an older lot. What does not change it is us: the price we hand you in writing before work starts is the price on the final invoice. That is the Garrison Standard, and we do not work any other way.
Neighborhoods We Serve in Sunnyvale
We work across the full city, and the older ranch tracts make up most of our ADU and addition work. Response time for a site visit in Sunnyvale is typically within one to two business days, depending on permit and inspection volume at the city.
- Cherry Chase
- Lakewood Village
- Ortega Park
- Ponderosa Park
- Washington (near Sunnyvale Avenue and El Camino Real)
Service Area – Cities Near Sunnyvale
Our Sunnyvale crews also cover the surrounding Santa Clara County cities. Every city has its own permit office and its own quirks, so each project gets priced against that jurisdiction’s actual requirements, not a generic template.
We serve Santa Clara, CA, San Jose, CA, Saratoga, CA, and Campbell, CA directly.
Serving Sunnyvale, CA - Our Local Coverage Area
We’re based in the Sunnyvale 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 Sunnyvale
Sunnyvale is faster than most of Santa Clara County when the project uses the city’s pre-approved ADU plan options. A project that follows the Sunnyvale Standard can clear planning review in a matter of weeks, while a fully custom design takes longer. We tell you which path applies before you commit. Call (669) 201-3984 for a free estimate.
Some Sunnyvale neighborhoods have HOAs, and state ADU law overrides most HOA restrictions on accessory dwelling units. We review your specific situation before we price the job, and we flag any covenants that could slow the permit. It is part of the written estimate, not a surprise later.
Yes. We pull the permits, we meet the inspector on site, and we do not ask for final payment until the city signs off. The Garrison Standard means the permit board is real, the inspection is passed, and the workmanship is guaranteed in writing for a full year. Call (669) 201-3984 to schedule a free estimate.
To get a written price for your Sunnyvale ADU, garage conversion, or room addition, call (669) 201-3984. A live person answers around the clock, and we will schedule your free estimate without a callback queue.
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 Sunnyvale Customers Say
"Insulation, drywall, and finishes were all well done. Feels like part of the house."
- Pete O."Garage conversion with a new bath and kitchenette. Permit was handled by them. Inspection passed first time."
- Sheila B."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.
