Home Additions & ADU in Sunnyvale - One Fixed Price, Permits Handled

Fast, Reliable Home Additions & ADU Across Sunnyvale

Home additions and ADU construction in Sunnyvale, Texas typically run $45,000 to $130,000 for a room addition, and $90,000 to $220,000 for a new detached ADU. The spread comes down to square footage, site conditions, and whether the job is a simple bump-out or a full second-story frame-up with a new foundation. We’ve worked Sunnyvale’s older ranch neighborhoods and its newer developments long enough to know which lots drain fast and which ones will need extra grading before a slab ever gets poured.

Call (877) 610-1318

If you’re in Sunnyvale and weighing a home addition or ADU, call Tom Barrett’s team at (877) 610-1318 for a straight answer and a free estimate. We’re the kind of contractor who shows up, looks at your lot, checks the setback lines, and tells you what’s actually possible before you spend a dime on design fees.

Key Takeaways:

• Home addition pricing in Sunnyvale runs $45,000-$130,000, and a detached ADU runs $90,000-$220,000.
• We handle ADU design, permitting, garage conversions, second-story additions, and sunrooms across the entire Sunnyvale market.
• Every eligible job gets permits pulled and inspections signed. Every scope change comes as a written change order before work starts.
• Barrett & Sons has been owner-operated since 1998. Tom’s sons run the crews, and Tom answers the phone.

Why Barrett & Sons Construction Is Sunnyvale’s Preferred Home Additions & ADU Company

Sunnyvale homeowners don’t need another contractor who quotes one number on the phone and shows up with another. That’s the exact reason Tom Barrett started this company in 1998, and the reason he still puts his name, address, and license number on every contract. Ask anyone on your street, or look up the license number yourself. We’ve earned our reputation in Sunnyvale by doing what we said we’d do, in writing, on time.

When you call us about a home addition or ADU in Sunnyvale, you get a live person. Not a voicemail box, not an out-of-state call center. We answer 24/7. And because our crews are Tom’s sons and their teams, background-checked and uniformed, the people who show up at your door carry the Barrett name on the truck. They’re accountable to you because they’re accountable to their father.

Our work in Sunnyvale is backed by the 90-Day Done Right Promise, written on every construction and remodeling contract. If something isn’t done right, Tom comes back and makes it right. One call. No fine print. We also offer a permanent 10% Senior & Veteran discount, a free second opinion on any written estimate, and no trip charge inside the county.

Sunnyvale sits on Dallas County clay soils that swell and shrink with the seasons. We’ve worked enough foundations here to know what that means for an addition: piers have to be sized for the soil, not for a bargain. That’s why we don’t take shortcuts on footings, and why the permit inspector works for you, not for me.

Our Home Additions & ADU Services in Sunnyvale

We’re the Home Additions & ADU team Sunnyvale homeowners call when they need real square footage, not a suggestion. Here’s what we handle most often.

ADU Design & Permitting

Accessory dwelling units in Sunnyvale are a smart move for aging parents, adult kids, or rental income. We handle the full design and permitting process, including submittals to the Town of Sunnyvale and coordination with any utility upgrades. Before you commit, we walk your lot for setbacks, easements, and drainage. A detached ADU in Sunnyvale typically runs $90,000 to $220,000 depending on size, finishes, and foundation scope. We put every allowance in writing before you sign, and every price change comes as a written change order before work proceeds.

Garage Conversion ADU

Converting an existing garage is often the fastest route to extra living space in Sunnyvale because the shell is already there. But older Sunnyvale garages come with complications: slab elevations below grade, no insulation, original electrical that won’t pass current code. We’ve converted enough garages in this town to know what inspectors look for. A garage conversion ADU in Sunnyvale typically runs $30,000 to $80,000. We handle the structural reinforcement, plumbing rough-in, panel upgrades, and all required inspections.

New Detached ADU

If you have the lot depth, a new detached ADU gives you a separate address, separate utilities, and no shared walls. In Sunnyvale, that means slab-on-grade foundations engineered for expansive clay soils, with proper drainage and a roof tied to current wind and energy codes. New detached ADU construction typically runs $90,000 to $220,000. We specify materials that make sense for Sunnyvale’s climate: marine-grade exterior hardware, sealed paver joints where applicable, and framing schedules that hold up to Texas heat.

Junior ADU & Interior Conversion

A Junior ADU, or JADU, converts existing interior space, like a spare bedroom, den, or attached storage area, into a self-contained living unit. It’s the most economical way to add rental income or a private suite for family in Sunnyvale. Because the conversion happens inside the existing envelope, permitting moves faster than a ground-up build. We handle the plumbing, kitchenette, bathroom, and separate entrance details. Pricing depends heavily on your home’s existing layout and usually starts below a full detached ADU.

Trusted Brands We Service in Sunnyvale

We don’t install mystery materials off a van. When we build an addition or ADU in Sunnyvale, we use brands you can look up: Schluter for waterproof shower and tile systems, Sterling for plumbing fixtures in the kitchen and bath, and Grohe for faucets and shower components that hold up to Texas water conditions. If the project calls for roofing tie-ins, we use GAF products. We keep fast-turnaround access to these brands for our Sunnyvale customers because the last thing you want is a three-week delay waiting on a shower valve.

Common Home Additions & ADU Problems We See in Sunnyvale Homes

• Expansive clay soil under the slab. Sunnyvale sits on Dallas County clay that moves with moisture. A room addition framed without properly sized piers can crack at the seam within two wet seasons. We size footings and piers to the soil, not to a flat price from a generic plan.
• Original electrical panels that can’t carry the load. Most 1970s and 1980s Sunnyvale homes have 100-amp panels. Add a kitchenette, a mini-split, and an electric oven in a new ADU, and you’re overloaded. We plan panel upgrades into the scope from day one so it’s a line item, not a surprise.
• Drainage routing through low lots. Some low-lying Sunnyvale lots hold water after a hard rain. A poorly drained addition can start wicking moisture into the baseplate within a year. We check grade, erosion, and storm runoff before we ever pour.
• Setback and easement miscalculations. Sunnyvale’s lot lines don’t always match the fence lines. We pull the actual survey before design, so your addition doesn’t end up six inches into a utility easement and stuck in permitting limbo.

Pricing for Home Additions & ADU in Sunnyvale, TX

We Also Serve Cities Near Sunnyvale

Barrett & Sons Construction serves Sunnyvale and the surrounding communities, including Mesquite, Balch Springs, Forney, and Rowlett. If you’re a few miles over the line and wondering whether we’ll come out, the answer is almost always yes. We schedule across the eastern Dallas County area every week, so adding your street to our route is rarely a problem.

FAQs - Home Additions & ADU in Sunnyvale