A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Sunnyvale, TX
Sunnyvale’s ADU potential is different from most Dallas-area suburbs. The town’s 2016 adoption of the International Residential Code opened a clear path for backyard cottages and garage conversions, but the real story is the housing stock: post-1970 brick veneer ranch homes on wide lots, built for a different era. We’re Fielding ADU Builders, an independently owned member of the Garrison Partners family, and we handle ADUs, garage conversions, and room additions here under The Garrison Standard: a written price before any work starts, permits done by the book, and a 365-day written guarantee. Call (903) 342-8977 for a free estimate.
Why Sunnyvale Homes Are Different
Sunnyvale jobs don’t look like jobs in Mesquite or Rowlett. The lots are larger, the houses are newer, and the challenges are specific. Most single-family homes in Sunnyvale went up after 1970, which means the framing and foundation work is generally predictable. The complication is the electrical service on the east side: homes built before 1985 frequently still carry 3-wire service, so an ADU or garage conversion almost always starts with a panel upgrade before we touch anything else. That’s a real cost item we flag early, not a surprise at the end.
The lot sizes work in your favor. A wide lot means a detached ADU can go up without crowding the primary house, which keeps privacy intact and usually clears Sunnyvale’s setback requirements without needing a variance. The trade-off is soil: Sunnyvale sits on expansive clay that swells when wet and shrinks in drought. Slab-on-grade ADUs need foundation design that accounts for that movement, or you’ll see cracking within a few Texas summers. We design for it from day one.
Sunnyvale’s summers also shape how we build. High humidity and long stretches above 95 degrees mean a cheap window unit won’t hold up in a backyard cottage. We spec high-efficiency mini-split systems and sun-reflective roofing on nearly every detached ADU we build here, because those are the choices that keep the space usable in August without a $400 electric bill.
Our Main Sunnyvale Services
The three jobs Sunnyvale homeowners call us about most are room additions, garage conversions, and detached ADUs. Each has its own Sunnyvale page with local pricing and details, but here’s the quick picture.
Room Addition Contractor in Sunnyvale
A room addition in Sunnyvale means tying into a post-1970 ranch home, which is usually straightforward framing work. The variables are foundation engineering on clay soil and matching the existing brick veneer so the addition doesn’t look bolted on. We handle permits, and we hand you a written price before the first crew member arrives. Read the full breakdown on our Room Addition Contractor in Sunnyvale page.
Garage Conversion Contractor in Sunnyvale
Garage conversions in Sunnyvale carry one extra step most homeowners don’t expect: insulation and seismic bracing upgrades to meet current code. A garage built in 1980 was never insulated to living-space standards, and bringing the walls and slab up to IRC requirements is usually the difference between a rough quote and an honest one. We do that work as part of the conversion. Details are on the Garage Conversion Contractor in Sunnyvale page.
ADU Builders in Sunnyvale
Detached ADUs are where Sunnyvale’s wide lots shine. We work with prefab platforms like Boxabl and Plant Prefab when speed matters, and we do conventional builds with James Hardie siding when the lot or design calls for it. Foundation work on Sunnyvale’s clay soil is the part we won’t shortcut. See the full scope and pricing on our ADU Builders in Sunnyvale page.
Every one of these jobs follows The Garrison Code: show up in the window, price in writing, by the book, leave it clean, stand behind it for a year. Reed Calloway leads our crew, and every technician is background-checked and uniformed before they set foot on your property.
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 service ADUs and structures from Mighty Buildings, Boxabl, and Tuff Shed in Sunnyvale. Most components ship quickly to the Dallas-Fort Worth metro, and we coordinate delivery and installation so you don’t have to chase freight windows. See our brands for the full list we work with.
Pricing for ADU Company in Sunnyvale, TX
Every Sunnyvale project gets a written price before any work starts – that’s the Garrison Standard, not an add-on. The table below reflects typical ranges we see in this market.
| Service | Typical range in Sunnyvale |
|---|---|
| Detached ADU (prefab, 400 – 600 sq ft) | $140,000 – $210,000 |
| Detached ADU (conventional build, 400 – 600 sq ft) | $220,000 – $310,000 |
| Garage conversion (basic, no structural changes) | $70,000 – $110,000 |
| Garage conversion (with structural and insulation upgrades) | $110,000 – $160,000 |
| Room addition (200 – 400 sq ft) | $90,000 – $140,000 |
| Room addition (400 – 600 sq ft) | $150,000 – $220,000 |
| Panel upgrade (3-wire to 200-amp) | $3,500 – $6,000 |
| Foundation engineering for clay soil | $4,000 – $8,000 |
Three things push price up in Sunnyvale: a panel upgrade on pre-1985 east-side homes, foundation work on expansive clay, and code-required insulation upgrades on older garages. We name every one of them in the written estimate before you commit. The number you approve is the number on the final invoice – no change orders, no door-price surprises. Call (903) 342-8977 for an exact figure.
Neighborhoods We Serve in Sunnyvale
We work across all of Sunnyvale, including most of the established subdivisions and new-build pockets. Response time is typically one to two business days for a site visit.
- The Meadows
- Greenbelt
- Old Town
- Chimney Hill
- Sunnyvale East
Service Area – Cities Near Sunnyvale
Fielding ADU Builders serves Sunnyvale and the surrounding communities. Our crews also cover Mesquite, TX, Seagoville, TX, Sachse, TX, and Irving, TX. Scheduling is coordinated from our Dallas-Fort Worth office, with crews dispatched locally to Sunnyvale.
Serving Sunnyvale, TX - 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
Most Sunnyvale projects go from signed contract to first foundation work in three to six weeks, depending on permit review time with the town. Prefab ADUs from Boxabl or Mighty Buildings can compress that timeline since the structure ships partly assembled. Call (903) 342-8977 and we’ll give you a realistic window for your specific lot.
Many Sunnyvale subdivisions have HOA covenants, and some restrict detached structures. We don’t file HOA paperwork for you, but we’ll flag early whether your plat has restrictions that could slow a permit. The written price covers the build, not the HOA review. Call (903) 342-8977 to talk through your neighborhood.
Yes. On pre-1985 east-side Sunnyvale homes with 3-wire service, the panel upgrade comes first, because the ADU can’t pass inspection on the old service. We include that line item in the written estimate so you see it up front. Call (903) 342-8977 for a free estimate that covers it.
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
"Foundation and slab poured on schedule. Crew kept the yard orderly."
- Marian J."Clear price breakdown. Change orders were all in writing."
- Hal P."Good addition. Electrical inspection delayed a week, which was the county, but the build is great."
- Eva K.
