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 Austin
Home additions and ADU construction in Austin typically run $45,000-$130,000 for a room addition and $90,000-$220,000 for a detached accessory dwelling unit, with garage conversions landing between $30,000 and $80,000. Those are real numbers from this market, not national averages. If you’re weighing a second-story addition in Travis Heights, an ADU behind a 1940s bungalow in Hyde Park, or a garage conversion in Wells Branch, you need a contractor who understands that Austin’s soil, tree ordinances, and permit process punish guesswork. Call Barrett & Sons Construction at (877) 610-1318 for a written, line-item estimate before you commit to anything.
We’ve been building Home Additions & ADU projects in this city long enough to know exactly where the surprises hide. Austin is not a simple place to build. The hill country limestone west of I-35, the black gumbo clay east of it, the Heritage Tree reviews, the summer pour windows - all of it affects your cost, your schedule, and your foundation strategy. We plan for that up front and put every allowance in writing before the first shovel breaks ground.
Why Barrett & Sons Construction Is Austin’s Preferred Home Additions & ADU Company
Tom Barrett started this company in 1998 as an owner-operated shop, and it still runs that way. Tom’s sons lead the crews, Tom’s name is on the truck, and Tom’s phone number is answered by a live person 24 hours a day, seven days a week. If you call about a foundation question in 78721 at 9 p.m. on a Saturday, you get a person, not a voicemail box. That matters to homeowners in Austin who’ve been burned by a national chain quoting one price on the phone and showing up with a different number at the door.
We serve all of Austin - 78719, 78720, 78721, 78722, and every neighborhood in between. Our crews know the difference between building on limestone shelf in Jollyville and expansive clay in Hornsby Bend, because they’ve poured footings in both. Every job we take includes permits pulled and inspections signed, and every price change arrives as a written change order before work proceeds. No surprise invoices. The permit inspector works for you, not for me - that’s why I like him.
Our 90-Day Done Right Promise gets written on every contract. If something isn’t done right, one call brings Tom back. That’s the whole promise, in plain English.
Our Home Additions & ADU Services in Austin
ADU Design & Permitting
An ADU in Austin is a different animal than an ADU in Round Rock or San Antonio. Austin’s 2019-2023 ordinance changes now allow by-right accessory dwelling units on most single-family lots, but the city’s Heritage Tree Ordinance can stall a project for weeks if a protected live oak sits anywhere near your construction zone. We handle the arborist survey, the tree-mitigation paperwork, and the full permit package, and we give you a written schedule that includes permit review time. No vague timelines.
Garage Conversion ADU
Converting a garage in the older neighborhoods around Bouldin Creek or 78702 usually means discovering knob-and-tube wiring, undersized utilities, or a slab that was poured in 1952 and never meant to hold living space. We inspect for all of that before we quote, so your number is a real number. A typical Bathroom Remodeling in Austin project inside a garage conversion has to meet current code for ventilation and moisture, which adds cost that out-of-town GCs often miss. We don’t miss it, and it shows up on your estimate, not in a surprise change order.
New Detached ADU
A new detached ADU in east Austin sits on Blackland Prairie clay that swells and shrinks several inches per year. We use post-tensioned slab-on-grade or deep drilled piers, depending on what your soil report says. That’s not optional out here - it’s the difference between a floor that stays flat and one that cracks in year three. Expect $90,000-$220,000 for a complete, permitted, move-in-ready unit, depending on size, finishes, and site work.
Junior ADU & Interior Conversion
A junior ADU inside an existing footprint - a converted garage wing, a finished attic, a partitioned section of the main house - gets you a rental unit or a mother-in-law space without pouring new foundation. This is where Austin’s older housing stock actually works in your favor: many 1920s-1950s pier-and-beam homes have tall ceilings and distinct wings that convert cleanly. We also handle Kitchen Remodeling in Austin projects inside these conversions, because a standalone ADU needs a functioning kitchen, and we stock KraftMaid and Cambria lines for exactly that.
Room Additions & Second Story Additions
Adding square footage to a pier-and-beam bungalow in Hyde Park is not the same job as adding to a slab home in Anderson Mill. The foundation dictates everything - footings, framing, plumbing runs, electrical. For second-story additions, we go roof-off and engineer the load path from the existing walls up. For sunrooms and enclosed patios, we replace screens with insulated glass and climate control that handles a 100°F Austin August without sweating.
We also build sunrooms and enclosed patios in Austin proper, from Clarksville to the 78720 corridor. A sunroom without proper glazing on a south-facing wall turns into a solar oven by 2 p.m. in July. We spec Andersen windows and door systems that cut that heat load, then back the install with our written 90-Day Done Right Promise.
What happens when you call
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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 Austin
We install and service GAF roofing systems on ADU builds and room additions across Austin, because a GAF roof install eligible for the manufacturer’s warranty gives you a name you can look up, not a mystery brand off a van. In kitchens and baths inside additions and ADUs, we use Schluter waterproofing systems under tile and Sterling fixtures where the budget calls for solid, no-regrets quality. These are brands you can research before you sign - and we’re glad you will. Check the materials, check the license, check the reviews. Then call (877) 610-1318.
Common Home Additions & ADU Problems We See in Austin Homes
- Foundation soil movement: East Austin’s Blackland Prairie clay expands and contracts so aggressively through drought and flood cycles that slab cracks and wall separation are common even in homes built in the 1990s. Any addition on that soil needs a foundation strategy that matches the existing structure, or you’re building tomorrow’s foundation repair bill into today’s project.
- Heritage Tree stalls: In neighborhoods like Hyde Park and Travis Heights, a mature live oak within the critical root zone of your addition triggers a certified arborist survey and city review before ground disturbance. That process can take weeks, and out-of-town builders often don’t price that carrying cost into the bid. We do, and we write it on the schedule.
- Knob-and-tube and asbestos in older stock: Central Austin bungalows from the 1920s-1950s frequently hide outdated wiring and asbestos-containing materials behind walls that look fine from the curb. We test for both before we open walls, and we handle abatement and rewiring as part of the scope, in writing, before work starts.
- Undersized utilities: A 1948 house wasn’t built to carry the electrical load of a modern ADU with a full kitchen, laundry, and HVAC. We upgrade panels and service drops as part of the addition, so your new square footage doesn’t brown out the old house.
Pricing for Home Additions & ADU in Austin, TX
Here’s what you should budget in Austin. A standard room addition runs $45,000-$130,000 depending on square footage, foundation type, and finish level. A detached ADU runs $90,000-$220,000. A garage conversion lands between $30,000 and $80,000. A junior ADU or interior conversion can come in under those ranges if you’re working within existing framing. What moves the needle in Austin specifically: whether your site sits on limestone or clay, whether a Heritage Tree sits inside your build zone, and whether your existing structure needs electrical or abatement work. Every line item goes on the written estimate. Call (877) 610-1318 and Tom will walk you through the numbers himself. No trip charge inside the county.
We Also Serve Cities Near Austin
Based in Austin, our crews work Home Additions & ADU in Austin neighborhoods daily and regularly take on projects in nearby Hornsby Bend, Wells Branch, Anderson Mill, and Jollyville. If you’re just outside the city line and wondering whether we’ll come to you - call (877) 610-1318 and ask. If you’re inside Travis County, there’s no trip charge.
Serving Austin, TX - Our Local Coverage Area
We’re based in the Austin 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 Austin
A room addition in Austin typically runs $45,000-$130,000, while a detached ADU runs $90,000-$220,000 and a garage conversion lands at $30,000-$80,000. Austin’s split geology - limestone west of I-35, expansive clay east - is the single biggest local variable, because it dictates your foundation type before any framing starts. Call (877) 610-1318 for a line-item quote specific to your address. Estimates are free.
A detached ADU in Austin typically takes 6-12 months from permit application to final inspection, with Heritage Tree review and soil engineering as the two most common schedule variables. East-side clay lots needing deep piers and west-side lots needing rock excavation both add days to the front end. We give you a written schedule that names those items so you’re not watching weeks disappear without explanation.
Every eligible job we build in Austin includes permits pulled and inspections signed. We don’t do under-the-table work, and we don’t tell homeowners permits are optional. The inspector works for you, not for me - that’s why I like him seeing our framing and our electrical before anything gets covered.
Not without a written change order signed by you first. Every scope, every allowance, every discovery is documented in writing before work proceeds. An allowance that isn’t on paper is a surprise waiting for a date - and we don’t do surprises. Call (877) 610-1318 for an exact written quote.
Yes. Every completed Barrett & Sons project carries our written 90-Day Done Right Promise. If something isn’t done right, one call brings Tom back to make it right. That promise is printed on the contract, not buried in the fine print. If you’re comparing bids in Austin, ask the other contractors what their written promise looks like. Then call us.
Get Your Free Estimate in Austin
If you’re planning a home addition, a garage conversion, or a detached ADU in Austin, call Barrett & Sons at (877) 610-1318. Tom Barrett or one of his sons will answer, ask about your property, and schedule a time to walk the site. You’ll get a written, line-item estimate with real numbers, a real schedule, and a name you can look up. We’re proud to serve Austin, and we’ll stand behind what we build long after the final inspection signs off.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Austin and surrounding communities since 1998.