Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
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After
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AfterFast, Reliable Home Additions & ADU Across Austin
Most room additions and ADUs in Austin run between $45,000 and $130,000, with detached new-construction ADUs typically falling in the $90,000 to $220,000 range and garage conversions between $30,000 and $80,000. Those numbers move fast once walls open on an older Central Austin bungalow, which is exactly why we write every allowance and every change order on paper before work starts. Barrett & Sons Construction has been owner-operated since 1998, and Tom Barrett’s sons run the crews that serve Austin’s 78719, 78720, 78721, and 78722 ZIPs. Call (877) 610-1318 and you’ll get a live person, not a voicemail box.
Why Barrett & Sons Construction Is Austin’s Preferred Home Additions & ADU Company
We’re the name-on-the-truck alternative to the big regional outfits that quote one number over the phone and show up with another. Tom Barrett publishes his name, his address, and his license number. Look it up before you sign anything. Our office coordinates scheduling and dispatch for Austin jobs locally, so the person who answers your call knows what happened on your last visit, not just what’s in a CRM note.
The 90-Day Done Right Promise sits on every contract we write. If something’s not right after we finish, one call brings Tom back. That matters more on a $90,000 ADU than it does on a $400 roof repair, and we treat both the same way. Ask anyone in Austin who has had an addition go sideways: the contractor’s willingness to come back is worth more than the savings on the front end.
Our crews are background-checked, uniformed, and carry the Barrett & Sons name on their trucks. Tom’s sons are on-site most days. You won’t get a different crew every morning and a project manager on a headset three states away. You get the same faces, every day, until the final inspection signs off.
Our Home Additions & ADU Services in Austin
ADU Design & Permitting
Since Austin relaxed its accessory dwelling unit rules between 2019 and 2023, most single-family lots in the city can now host a by-right ADU. But the path from lot line to permit sign-off involves the city’s site plan review, stormwater rules, and often a Heritage Tree Ordinance check. We handle the full permit package. If you live in Hyde Park or Clarksville and the design comes within a protected live oak’s critical root zone, we’ll bring the arborist survey into the plan before the city asks for it. That’s the difference between a permit that takes weeks and one that takes months.
Garage Conversion ADU
Converting an attached garage in an Austin home from the 1950s or 60s brings the same questions every time: slab condition, insulation, and whether the old garage roof ties into the main house properly. East of I-35, a garage slab poured on Blackland Prairie clay often has hairline cracks that don’t threaten the structure but do change how we approach plumbing and finishes. A garage conversion in Austin typically runs $30,000 to $80,000 depending on whether you need a full kitchen rough-in or just a bedroom and bath.
New Detached ADU
Building a new detached ADU in Austin means choosing between pier-and-beam and slab-on-grade foundations, and the answer changes depending on which side of I-35 you’re on. West of the highway, we’re often drilling into limestone. East, we’re engineering for expansive clay. We pull every permit, schedule every inspection, and write the foundation scope into your contract before a shovel hits the ground. New detached ADU construction in Austin runs $90,000 to $220,000 for a completed unit with a kitchen, bath, and separate meter.
Junior ADU & Interior Conversion
A junior ADU, or JADU, converts existing space inside the primary home into a small independent unit, typically under 500 square feet. In Austin’s 78721 and 78722 ZIPs, where mid-century ranchers and postwar cottages dominate, we see a lot of owners carve out a back bedroom plus a kitchenette and a separate exterior entrance. This is the most budget-friendly path to rental income, and it still requires city review for egress, fire separation, and a compact kitchen. We walk the property first, tell you what the city will require, and put the numbers in writing.
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 stock and install materials from brands you can look up, not mystery products off a van. For Austin’s heat and humidity, we specify GAF roofing on any addition that extends or ties into the existing roofline, because the UV exposure in Travis County is brutal on membranes that aren’t rated for it. In bathrooms and wet areas inside your new ADU, we install Schluter waterproofing systems under tile rather than cheaper roll-on membranes that fail at the corners. And for sinks and faucets on addition projects, Grohe fixtures hold up to Austin’s hard water better than most imported brands. Parts are stocked locally in Austin, so when a fixture fails under warranty, we’re not waiting on a freight shipment from two states away.
Common Home Additions & ADU Problems We See in Austin Homes
- Knob-and-tube wiring hiding in the walls. Central Austin ZIP codes like 78702 and 78704 are full of 1920s and 1930s bungalows that still carry original wiring. Once a wall comes open on an addition or second-story project, the city now requires full replacement of any exposed knob-and-tube before the inspection will sign off. That’s a real line item we write into the allowance sheet before work starts.
- Expansive Blackland Prairie clay under the slab. East of I-35, the soil swells and shrinks enough through Austin’s drought-to-flash-flood cycles to move several inches vertically in a single year. Additions on that side of the city need post-tensioned slabs or deep drilled piers. A contractor who pours a standard slab east of I-35 is building a future foundation repair call.
- Heritage Tree Ordinance review stalling permits. Austin protects live oaks and other natives over 19 inches in circumference. If your addition or ADU site plan encroaches on a protected tree’s critical root zone in Hyde Park, Bouldin Creek, or Travis Heights, the city requires a certified arborist survey before it will release the permit. Out-of-town contractors get blindsided by the delay. We factor it into the schedule up front.
- Undersized utilities on infill lots. The teardown-and-rebuild cycle in neighborhoods like Travis Heights means we often work on streets where the original water and sewer laterals are too small for an ADU’s added load. That means a tap upgrade, or even a new lateral to the main, before we can close the trench. We write that into the estimate when the property walkthrough shows the risk.
Pricing for Home Additions & ADU in Austin, TX
Here’s the honest version of what we quote across Austin for the work we do on additions and ADUs:
| Project | Austin Market Range |
|---|---|
| Home Addition | $45,000-$130,000 |
| ADU Construction (new detached) | $90,000-$220,000 |
| Garage Conversion | $30,000-$80,000 |
Those ranges are wide because Austin’s geology is split. A second-story addition in 78720 on stable ground costs less than the same addition in 78721 on expansive clay that needs piers. The Heritage Tree Ordinance can add arborist surveys, mitigation fees, and root-protection plans that push a project weeks and thousands of dollars past a naive quote. We put every allowance in writing before the contract is signed, and if a surprise shows up once walls are open, you approve a written change order before we spend a dollar. Call (877) 610-1318 for a free estimate. We come out to your Austin property, walk the scope with you, and put line-item numbers on paper before you sign a thing.
We Also Serve Cities Near Austin
Barrett & Sons Construction runs Home Additions & ADU projects throughout Travis County and the surrounding area. If you’re in Hornsby Bend, Wells Branch, Anderson Mill, or Jollyville, we’ll schedule the same walkthrough and deliver the same written scope. The clay doesn’t end at the Austin city limit line, and neither does our service area.
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
The two big ones are knob-and-tube wiring that Austin’s building department now requires fully replaced once exposed, and asbestos in old drywall texture or floor tile on pre-1980s bungalows. In Central Austin ZIPs like 78702 and 78704, a room addition on a 1930s pier-and-beam home will usually trigger an electrical allowance of $3,000 to $6,000, plus abatement if the test comes back positive. We test before we quote, and the allowance covers it. Call (877) 610-1318 if you want us to walk your bungalow and put those numbers on paper.
It changes everything. West of I-35, shallow footings hit limestone so dense that rock saws or blasting are required, even for a modest one-room addition. East of I-35, the Blackland Prairie clay expands and contracts so aggressively with Austin’s rainfall cycles that post-tensioned slabs or deep drilled piers are standard practice. Two different foundation strategies, same city. We design for whichever side of the fault line your lot sits on. Get a free estimate at (877) 610-1318 and we’ll explain exactly what your side requires.
On older Austin homes, almost always. The city will not sign off on a final inspection if the newly exposed portion of an existing circuit still runs knob-and-tube, and adding a second story means opening walls and ceilings that haven’t been touched since the Roosevelt administration. On a 1930s pier-and-beam bungalow in Travis Heights, we opened the wall for a second-story addition and found knob-and-tube wiring tangled with a previous owner’s unpermitted splice. Our crew shut down that circuit before touching the framing, wrote a $4,200 change order for new Romex and an electrical rough-in, and kept the project on schedule by coordinating the city inspection sign-off before we closed the wall. That’s how we work. Call (877) 610-1318 to get a scope that already accounts for what the permit will trigger.
Because Austin’s ordinance protects live oaks and other native trees at 19 inches in circumference or larger, and the city will not release a permit for any ground disturbance within a protected tree’s critical root zone without a certified arborist survey and a root-protection plan. Hyde Park has dense mature tree coverage on nearly every lot, so a routine ADU or addition will frequently trigger the review even when the tree is on the property line, not in the build footprint. We bring the arborist in during the design phase, not after the city bounce-back. The survey costs a few hundred dollars and saves weeks. Call (877) 610-1318 and we’ll tell you whether your lot will trigger it before you commit.
Yes, but we schedule pours before 7 a.m. in July and August. Austin’s 100-degree-plus heat accelerates hydration so fast that a mid-afternoon pour will cure prematurely, shrink, and crack, especially on the dry limestone side west of I-35. Our crews are used to setting up while it’s still cool, and we adjust the mix for temperature. It’s one of those local details that doesn’t show up on a national cost estimator but shows up on your slab six months later if it’s ignored. Call (877) 610-1318 for a free estimate and we’ll walk you through the whole schedule for your Austin addition or ADU.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Austin since 1998.