Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
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AfterFast, Reliable Home Additions & ADU Across Round Rock
Adding a room or a full ADU in Round Rock typically runs $45,000 to $130,000, and the two details that decide whether the project holds up are the wind-load connections and the clay-soil foundation work. We’re Barrett & Sons Construction, founded in 1998 and owner-operated by Tom Barrett. Tom’s sons run the crews that build in Round Rock neighborhoods like Forest Creek, Teravista, and Stone Canyon every week. If you’re planning an addition or accessory dwelling unit, call (877) 610-1318 and we’ll walk the site with you before anyone swings a hammer.
The single biggest mistake we see in Round Rock is an addition or ADU poured on a separate floating slab without doweling into the main post-tension slab. On Blackland Prairie clay, that seam moves differently than the house, and within one drought-wet cycle you get a step crack at the connection point. We’ve torn out and rebuilt enough of those to know the fix isn’t cosmetic. We engineer the slab-to-slab connection from the first drawing, not as a patch after the inspector catches it.
Why Barrett & Sons Construction Is Round Rock’s Preferred Home Additions & ADU Company
Tom Barrett publishes his name, address, and license number. You can look them up before you sign anything. That’s how we’ve built a 29-year reputation in Central Texas without a franchise behind us. The crew that shows up at your door in Round Rock carries the Barrett & Sons name on their shirts and their background checks on file. Tom’s sons are on-site most days, not dialing in from a regional office.
Round Rock homeowners have told us stories about contractors who quoted one number on the phone and handed them a different bill at the door. That doesn’t happen here, because every scope change, every allowance, and every price adjustment arrives as a written change order before work proceeds. The allowance that isn’t on paper is a surprise waiting for a date. We’d rather have the hard conversation up front than the angry one at the end.
Our 90-Day Done Right Promise is written on every contract. If something isn’t done right, one call brings Tom back to make it right. No fine print, no phone tree. We answer our own phone 24 hours a day, and the person who picks up knows the difference between a Teravista lot and a Forest Creek lot because we’ve built on both.
Our Home Additions & ADU Services in Round Rock
ADU Design & Permitting
A detached ADU in Round Rock starts with Williamson County permitting and a site plan that accounts for clay-soil movement and wind-load requirements. We handle the drawings, the permit pull, and the inspections. The permit inspector works for you, not for me, which is exactly why we want him on the job. Our Home Additions & ADU team walks every Round Rock project through design review before the first concrete pour.
Garage Conversion ADU
Converting a garage into a junior ADU is the most cost-effective path to a rental unit or in-law suite in Round Rock, with typical costs of $30,000 to $80,000. But the conversion only works if the garage slab is properly tied to the main house slab and the removed wall is replaced with an engineered beam. We’ve seen non-engineered conversions in the 78664 and 78665 zips sag within two years on expansive clay, cracking drywall from the living room ceiling outward. Our conversions get a load-bearing beam with LTP4 tie-downs and a Simpson H2A hold-down at the header, rated for the wind loads Round Rock code requires.
New Detached ADU
A new detached ADU in Round Rock runs $90,000 to $220,000 depending on square footage, finishes, and lot conditions. The site prep matters more than the framing. On former Williamson County farmland, the original builder grading often left negative drainage toward the foundation, and after 15 to 20 years of clay-soil cycling, you have to regrade the lot perimeter and extend downspout drainage before any structural work can hold. We budget for that up front, not as a change order surprise midway through.
Junior ADU & Interior Conversion
A junior ADU carved out of an existing bonus room or attached suite is the most affordable home addition path in Round Rock. We convert interior space into a self-contained unit with its own entrance, kitchenette, and bath, with costs in the $45,000 to $130,000 range depending on whether plumbing stacks and electrical panels are already in place. The catch on a junior ADU in Round Rock is the same as any addition: the connection to the main post-tension slab has to be engineered, not guessed at.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
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You get an upfront price rangeHonest numbers before anyone is dispatched.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
Trusted Brands We Service in Round Rock
We install materials you can look up, not mystery brands off a van. For hardscape and site prep on Round Rock ADU projects, we routinely use Techo-Bloc and Cambridge Pavers for pavers and retaining walls, and Quikrete products for concrete repair and post-tension slab work. These are brands with published specifications for expansive soil conditions and Central Texas heat, which matters when summer temperatures top 100°F and pour windows compress. We stock the common parts for Round Rock additions locally, so a missing tie-down or paver course doesn’t stall your project for a week.
Common Home Additions & ADU Problems We See in Round Rock Homes
Here’s what we actually find when we walk a Round Rock addition or ADU site, before we quote.
- Floating slab ADUs with no doweling. A separate slab poured alongside the main post-tension foundation moves independently on Blackland Prairie clay. Within one wet-dry cycle, you get a step crack at the seam that no caulk or patching will fix. We dowel every slab-to-slab connection with epoxy-set reinforcement.
- Second-story additions with unrated rafter ties. The gable end of any Round Rock second story sits in the path of severe thunderstorm uplift. Missing hurricane clips or untrated ties let the roof sheathing pull nails and open a water intrusion path before the inspector ever arrives. Our Home Additions & ADU in Round Rock work always includes the rated hardware on the gable end, full stop.
- Garage conversions where the garage slab sits lower than the house slab. We see this constantly in Teravista and other tract-built subdivisions. The original builder set the garage 4 inches below the house, and a naive conversion creates a trip hazard and a drainage path toward both structures. Our crews core through the post-tension slab on the addition side, install a poured transition step with epoxy dowels, and regrade the front walk for positive drainage.
- Deferred drainage correction disguised as a remodel. In east-side subdivisions like Forest Creek, the original grading often ran negative toward the foundation. After 15 to 20 years of clay cycling, what a homeowner calls a room addition actually requires regrading the entire lot perimeter first. If you skip that step, your new addition inherits the old drainage problem, and the first heavy rain finds the seam.
Pricing for Home Additions & ADU in Round Rock, TX
| Project Type | Typical Round Rock Range |
|---|---|
| ADU Site Prep & Utilities | $7,000 - $18,000 |
| Garage Conversion ADU | $30,000 - $80,000 |
| Second Story Additions | $45,000 - $130,000 |
| New Detached ADU | $90,000 - $220,000 |
Every quote includes permits pulled, inspections signed, and written change orders before any scope change. We offer a Free Second Opinion on Any Written Estimate and a permanent 10% Senior & Veteran discount. Call (877) 610-1318 to schedule your free estimate. We’ll give you a written line-item quote so you can see exactly where the money goes.
We Also Serve Cities Near Round Rock
Our crews build additions and ADUs in Hutto, Georgetown, Brushy Creek, and Pflugerville as well as Round Rock. Dispatch and scheduling are coordinated from our Austin office, but our crew members live and work in Williamson County. If you’re a few miles outside city limits on county land, same soil, same wind-load requirements, and same permitting process. Call us and we’ll tell you straight what your specific property needs.
Serving Round Rock, TX - Our Local Coverage Area
We’re based in the Round Rock 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 - Home Additions & ADU in Round Rock
Round Rock code requires roof connections on additions to meet a 115 mph wind-load rating, per the adopted International Residential Code with local amendments for Williamson County. A compliant quote includes LTP4 tie-downs, hurricane clips on every rafter, and a Simpson H2A hold-down at the gable end header. A cheap quote omits these and hopes the inspector doesn’t notice. Call (877) 610-1318 and we’ll show you the hardware line item on paper before you sign.
Blackland Prairie clay is montmorillonite-heavy soil that swells during wet seasons and shrinks sharply in drought, generating constant slab movement. Any ADU foundation in Round Rock must be tied to the main post-tension slab with epoxy dowels and engineered reinforcement, or the two structures will move independently and crack at the seam. We’ve watched floating-slab ADUs step-crack after a single drought-wet cycle. Our quote includes the doweling and the engineering sign-off, not just the concrete pour.
Yes. Any garage conversion into a dwelling unit in Round Rock requires a Williamson County building permit, and the work must show an engineered beam substitution for any removed load-bearing wall, plus a compliant tie-down plan. Unpermitted conversions in the 78664 and 78665 zips are the first thing a resale inspection flags. We pull every permit and sign every inspection. Call (877) 610-1318 for a free estimate on a permitted conversion.
In Forest Creek and similar 78664 subdivisions, site prep starts with a drainage correction, because the original builder grading often ran negative toward the foundation. You need positive slope away from both the existing slab and the new addition, downspout extensions, and sometimes a perimeter regrade before concrete can be poured. We budget the site prep as its own line item so it’s clear on paper before the first day of work. Estimates are free at (877) 610-1318.
Documented wind-load compliance with the 115 mph rating, including the tie-down schedule and the final inspected sign-off, gives your insurance carrier evidence that the addition was built to local code. That can prevent a premium increase or coverage dispute after a severe thunderstorm claim. Without documentation, the adjuster assumes the roof connection was never inspected. We hand you that paperwork at job close, and it stays with the house at resale. For an exact quote, call (877) 610-1318.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Round Rock since 1998.