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 Lakeway
Adding square footage or building a detached ADU in Lakeway runs $45,000 to $130,000 for a home addition and $90,000 to $220,000 for a new ADU, and the job takes four to ten months depending on rock, trees, and permitting. If you’re on a sloped Edwards Plateau lot above Lake Travis, those numbers shift with drilled piers, retaining walls, and LCRA setbacks that flat-lot builders never touch. We’ve been framing additions and ADUs across the 78738 corridor for years, and we know which lots hit limestone at four feet and which ones hide heritage live oaks that can stop a foundation cold. Call (877) 610-1318 and Tom or one of his sons will walk your lot with you before you sign anything.
Why Barrett & Sons Construction Is Lakeway’s Preferred Home Additions & ADU Company
We’re the owner-operated outfit where the name on the truck is the name on the contract. Tom Barrett founded this company in 1998, and his sons run the crews that build in Lakeway. When you call about an ADU off Lakeway Drive or a second-story addition near the Hills of Lakeway, you talk to a person who knows your street, not a call center reading a script.
Lakeway homeowners hire us because we publish our license number and our address. Look us up before you sign anything. Ask anyone on your street. The permit inspector works for you, not for me – that’s why I like him. Every addition and ADU we build in Lakeway gets permits pulled and inspections signed, and every price change arrives as a written change order before a single nail moves. No surprise invoices at the end. That’s been our rule since 1998.
We answer the phone live, 24/7. When you’re mid-project and a stop-work order threat appears because someone disturbed a live oak root zone, you need a real person on the line, not a voicemail box. We are that person.
Our Home Additions & ADU Services in Lakeway
New Detached ADU
A detached ADU on a Lakeway hillside is a different animal than one on a flat Austin suburb lot. We set drilled concrete piers into Edwards Plateau limestone, which handles the slope but adds days to the foundation phase. On a sloped lot off Lakeway Drive, our crew kept the foundation outside the root zone of a 26-inch heritage live oak, coordinated LCRA waterfront setback review, and brought in a stormwater engineer to stay within impervious cover limits before we ever framed a wall. New detached ADUs in Lakeway typically run $90,000 to $220,000, with rock excavation, septic, and well setbacks driving the spread. Visit our Home Additions & ADU page for the full scope of what we build.
ADU Design & Permitting
Lakeway’s heritage tree ordinance protects live oaks 24 inches or larger in caliper. Before a detached ADU permit is issued, the city can require an arborist report and a foundation redesign if a protected tree sits within the root zone of your proposed slab. Contractors unfamiliar with Lakeway routinely underestimate this. We don’t. We file the arborist report, the stormwater plan, and the LCRA waterfront setback documents as one package, and we walk the permit through with you. Doing it wrong triggers stop-work orders, fines, and mid-project foundation re-engineering. Doing it right costs less, even before you count the headaches.
Garage Conversion ADU
Converting an attached garage into an ADU in Lakeway runs $30,000 to $80,000, and the big variable is the slab. Older garages in Lakeway’s late-80s and 90s stock often sit on slabs poured over shallow rock, which means cutting into limestone to run plumbing and electric. If a heritage live oak sits within 20 feet of the garage slab, we bring the arborist in before demolition starts. Root-zone disturbance during a conversion can trigger a stop-work order just as easily as it can during new construction. We scope that before quoting, not after the drywall’s down.
Junior ADU & Interior Conversion
A junior ADU inside the existing footprint – a converted bonus room, a finished attic, a mother-in-law suite carved from a large primary bedroom – is often the most cost-effective way to add a rentable or family unit in Lakeway. Because you’re not expanding the building envelope, impervious cover limits and LCRA setbacks rarely come into play. What does come into play is structural review: Lakeway homes on sloped lots settle differently than flat-lot houses, and we check existing foundation ties before we frame anything new. Figure $45,000 to $130,000 depending on plumbing, egress, and kitchenette scope.
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 Lakeway
We stock and install premium materials from brands you can look up yourself. For Lakeway ADUs and additions, that means Belgard and Techo-Bloc pavers for driveways, patios, and walkways tied into the new structure, and Quikrete products for pier forms and foundation work where the limestone demands custom mixes. We don’t load mystery brands off a van. When a Lakeway customer asks what’s going into their new ADU, we hand them the product spec sheet and the manufacturer’s name. That’s the Barrett & Sons standard, and it’s been that way since 1998.
Common Home Additions & ADU Problems We See in Lakeway Homes
- Rock excavation after the scope is signed. Builders unfamiliar with Lakeway quote for soil and hit solid limestone four feet down. Then the change order arrives for controlled blasting or hydraulic hammering, and the draw schedule blows up. We test-bore or review existing foundation records before quoting so the rock work is in the contract from day one.
- Skipping the arborist report. Disturbing a protected live oak root zone mid-dig triggers a stop-work order and fines from the city, and forces a mid-project foundation redesign. On sloped lots off Lakeway Drive and across the Hills of Lakeway, heritage oaks dot the terrain. We file the arborist report before the permit package goes in.
- Ignoring impervious cover caps. Lakeway enforces some of the tightest impervious cover limits in the Austin metro because runoff drains into Lake Travis. Adding a patio, driveway, or ADU roof area without stormwater engineering delays permit sign-off and can require costly drainage retrofits. We bring the stormwater engineer in during design, not after the inspector asks for one.
- Underestimating septic and well setbacks. Many Lakeway lots are on septic and private wells, not city sewer. County and city setback rules for a detached ADU can force the structure into a corner of the lot you didn’t plan for. We run the septic and well setback analysis before we draw the foundation.
Pricing for Home Additions & ADU in Lakeway, TX
Here’s what we see across Lakeway’s 78738 market, line by line. These are all-in ranges for scoped work, not teaser numbers.
| Project | Typical Range in Lakeway |
|---|---|
| Home Addition | $45,000 - $130,000 |
| ADU Construction | $90,000 - $220,000 |
| Garage Conversion | $30,000 - $80,000 |
What moves these numbers in Lakeway more than anything is rock. Limestone excavation, drilled piers, and foundation work on a cut-and-fill lot can add $10,000 to $25,000 to an ADU versus a comparable build on flat Austin soil. Heritage tree reports and stormwater engineering add more. Septic and well work for a detached ADU can run $8,000 to $20,000 on top of structure cost, depending on setback requirements and soil percolation. We scope every one of these in writing before we quote – so the number you sign is the number you pay. Call (877) 610-1318 for a free estimate, and we’ll walk your specific lot before we talk price.
We Also Serve Cities Near Lakeway
Our crews build additions and ADUs across the Lake Travis corridor. We serve Home Additions & ADU in Lakeway and the surrounding hill country, including Bee Cave, Lago Vista, Shady Hollow, and the west side of Austin. If you’re within 30 minutes of our Austin area dispatch, we’ll come walk your lot and scope the job the same way we do in Lakeway – permits pulled, change orders in writing, and a real person answering the phone when you call.
Serving Lakeway, TX - Our Local Coverage Area
We’re based in the Lakeway 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 Lakeway
Lakeway caps the total impervious cover on your lot – roof area, driveways, patios, pool decking – to protect Lake Travis water quality. Adding a garage or detached ADU increases your impervious footprint, which means the city can require a stormwater plan and possibly drainage improvements before the permit is issued. On sloped lots, that often includes engineered swales or retention features. We bring the stormwater engineer in during design so the permit goes through without a surprise retrofit. Call (877) 610-1318 and we’ll check your lot’s current impervious cover ratio before you commit.
Detached ADUs in Lakeway typically require City of Lakeway building permits, and if your lot has septic or a private well, Travis County reviews those setbacks as part of the package. Some ADU work near the waterfront also triggers LCRA review. We coordinate all three authorities in one filing so you don’t chase paper. The first step is a free lot walk – call (877) 610-1318 and we’ll tell you exactly which permits your project needs.
If the builder didn’t plan for it, rock excavation can add two to four weeks to a Lakeway home addition and $10,000 to $25,000 in change orders. If the builder did plan for it – by test-boring or pulling existing foundation records before quoting – the rock work is already in the schedule and the delay is zero. That’s the difference between a contract written by someone who knows Lakeway limestone and one written by someone who doesn’t. We plan for rock before we quote.
Yes, but you’ll likely need an arborist report and possibly a root-zone protection plan before the city issues the permit. If excavation for plumbing or foundation work will disturb the protected root zone, the city can require a redesign that moves your trenching around the tree. We’ve converted garages in Lakeway with live oaks 15 feet from the slab – it takes planning and an arborist on the front end, not a panicked call after the inspector shows up. Call (877) 610-1318 and we’ll bring the arborist to your lot before we quote.
A new detached ADU in Lakeway runs $90,000 to $220,000 all-in, with septic and well setbacks adding $8,000 to $20,000 on top of the structural build. Rock excavation, drilled piers, heritage tree reports, and stormwater engineering pull the number toward the high end. On a sloped lot above Lake Travis, the foundation alone can run 20% to 30% more than the same ADU on flat ground. We write every allowance and every scope item into the contract before work starts, so the number you sign is the number you pay. Call (877) 610-1318 for a free, line-item estimate on your specific lot.
Call (877) 610-1318 today and we’ll set up a time to walk your Lakeway property, answer your questions about rock, trees, and watershed rules, and give you a written estimate for your home addition or ADU. Free estimate, no trip charge inside the county, and a live person on the other end of the line.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Lakeway since the company’s founding in 1998.