Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
Before
After
Before
After
Before
AfterFast, Reliable Home Additions & ADU Across Leander
A room addition or detached ADU in Leander, TX typically runs $45,000-$130,000 for a room addition, $30,000-$80,000 for a garage conversion, and $90,000-$220,000 for a new detached ADU. Those are honest local numbers, and they come from a crew that knows what it takes to build on Leander’s limestone. The big variable most homeowners never see coming sits eighteen inches underground. Call us at (877) 610-1318 for a free estimate, and we’ll tell you up front what your lot will actually need.
We’re Barrett & Sons Construction, and we’ve been working Leander long enough to know which subdivisions hit rock at two feet and which ones drain without a fight. That local knowledge changes how we price, how we schedule, and how we avoid the surprise change orders that out-of-town outfits don’t know to warn you about.
Why Barrett & Sons Construction Is Leander’s Preferred Home Additions & ADU Company
Tom Barrett started this company in 1998, and he still answers his own phone. His sons run the crews. When you call about a home addition in Leander, you’re not getting a sales rep in another state reading off a script. You’re getting someone who knows the difference between soil conditions in Crystal Falls versus Travisso, and who will tell you the truth even when it’s not what you want to hear.
Leander homeowners have trusted us for years because we put everything in writing before work starts. Your scope, your allowances, your change orders. Every price adjustment arrives on paper before a single nail moves. The “allowance that isn’t on paper is a surprise waiting for a date” is how we avoid it. It’s also why customers in 78641, 78645, and 78646 keep calling us back.
We carry our 90-Day Done Right Promise on every contract. If it’s not right, Tom comes back and makes it right. One call. No argument. That’s not a marketing slogan, it’s literally written on the contract.
Our Home Additions & ADU Services in Leander
ADU Site Prep & Utilities
Building a detached ADU in Leander almost always means trenching for water, sewer, and electrical lines. On the west side of 78641 and throughout much of the city, that trenching hits solid Edwards Plateau limestone or caliche at eighteen to twenty-four inches. We won’t quote below-grade work without a site-specific soil probe first. It’s the only honest way to price the job, and it’s saved our Leander customers thousands in change-order surprises.
New Detached ADU
A new detached ADU in Leander runs $90,000-$220,000 depending on square footage, finishes, and how much rock your lot throws at us. We handle the full build: foundation, framing, HVAC, plumbing, electrical, and finish work. Every permit gets pulled, every inspection gets signed, and every allowance arrives in writing before we spend it. For a growing family that needs room for aging parents or adult kids, a detached ADU in Leander can make more sense than adding on to the main house.
Garage Conversion ADU
Converting an attached or detached garage into living space runs $30,000-$80,000 in Leander. Your post-2005 tract home was likely built on a post-tension slab, which means the slab can usually support a garage conversion without major structural work. But you need to check HOA rules in master-planned communities first. We’ll walk you through that review process before we start drawing plans.
Room Additions
Leander room additions run $45,000-$130,000. Most of the homes in this city were built after 2005, which means their framing, electrical, and plumbing are newer than what you find in older Austin neighborhoods. But that also means they were often built to a price point with builder-grade fixtures. When we add a primary bedroom suite or a second story, we’re matching code, matching your home’s existing systems, and upgrading where it actually matters.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
- 2
You get an upfront price rangeHonest numbers before anyone is dispatched.
- 3
A background-checked tech heads outLicensed & insured, dispatched right away.
- 4
You approve before work beginsNothing starts until you say go.
Trusted Brands We Service in Leander
We install brands you can look up: Simonton, Ply Gem, and PGT windows and doors on our Leander additions and ADUs. These are not mystery brands off a van. We order them from local supply houses, which means faster turnaround for our customers in 78641 and 78645 when a window gets damaged or a door needs replacing mid-project. If something fails within the warranty period, we handle the claim and the reinstallation.
Common Home Additions & ADU Problems We See in Leander Homes
- Skipping the soil probe before trenching ADU utilities. Hitting limestone at 18 inches turns a one-day dig into a multi-day rock-excavation change order. We’ve seen it happen to other contractors in Leander more times than we can count.
- Ignoring HOA architectural review in communities like Travisso. A detached ADU built without approval can trigger a stop-work order and force a full redesign. The HOA fine is bad; the rebuild is worse.
- Adding a second story to a post-tension slab without a structural review. Many Leander tract homes were engineered for single-story loads only. You can’t just stack another floor on them without an engineer involved.
- Underestimating runoff on sloped limestone lots. The west side of 78641 has a lot of sloping lots that need engineered retaining walls and grading plans. Clay-flat suburbs never deal with this. Leander lots do.
Pricing for Home Additions & ADU in Leander, TX
Here’s what our Leander customers can expect, based on current local material and labor costs:
| Service | Typical Leander Price Range |
|---|---|
| ADU Construction (New Detached) | $90,000-$220,000 |
| Garage Conversion ADU | $30,000-$80,000 |
| Room Additions | $45,000-$130,000 |
What moves the needle most in Leander? Lot slope and soil condition, square footage, whether you need an engineered retaining wall, and your finish selections. A 400-square-foot ADU on flat clay with basic finishes will land near the bottom of that range. A 900-square-foot ADU on a sloping limestone lot with a full kitchen and custom cabinets will push toward the top. Call (877) 610-1318 and we’ll give you a written, line-item estimate based on your actual lot and plans.
We Also Serve Cities Near Leander
We’re based in the Austin metro and our crews work across Williamson County and the north hills. If you’re in Cedar Park, Lago Vista, Brushy Creek, or Anderson Mill, you’ll get the same Home Additions & ADU team and the same written pricing. The limestone doesn’t stop at the city line, and neither do we.
Serving Leander, TX - Our Local Coverage Area
We’re based in the Leander 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 Leander
Yes, you need a soil probe before any below-grade work on a detached ADU in Leander. The city sits on Edwards Plateau limestone, and hitting caliche or solid rock at 18-24 inches is common enough that experienced contractors in Leander won’t quote trenching or foundation work without one. A soil probe costs a few hundred dollars and can prevent a $5,000-$15,000 rock-excavation change order. Call (877) 610-1318 and we’ll schedule the probe as part of your free estimate process.
A room addition can be added to a post-tension slab in Leander if the structural review confirms the slab has capacity, but it’s not a guarantee. Many of Leander’s post-2005 tract homes were engineered for their original footprint only. We bring in a structural engineer before we pour anything, and we’ll tell you honestly whether your slab can handle the load. Call (877) 610-1318 for a free estimate with a structural assessment included.
Yes, you can convert a garage into an ADU in Crystal Falls, but you need HOA architectural review approval first. Crystal Falls and most master-planned Leander communities have design guidelines that govern exterior appearance, parking requirements, and what counts as an accessory dwelling. We’ve seen builders ignore this and get hit with stop-work orders. We’ll help you prepare the submission and get approval before we pull a single permit. Call (877) 610-1318 to start the review process.
A fair price for a new detached ADU in Leander’s 78641 zip code is $90,000-$220,000, with most projects landing between $120,000 and $160,000 for a complete one-bedroom unit with a kitchen and bath. The 78641 side of Leander includes sloped limestone lots in communities like Crystal Falls, so foundation and utility work can run higher than flat-lot builds on the east side. We’ll give you a written, line-item quote with no allowances hidden in the dark. Call (877) 610-1318 for an exact number.
A home addition can affect your original builder warranty if the structural warranty is still active, and you should check your specific warranty terms before we start. Most Leander post-2005 homes came with 1-year workmanship and 10-year structural warranties from the builder. Some warranties exclude any structural modification. We’ll review your warranty documents and design the addition to work within what’s still covered. Call (877) 610-1318 and we’ll walk you through it before any work begins.
Call Barrett & Sons Construction at (877) 610-1318 for a free, written estimate on your home addition or ADU in Leander. We’ll put the scope, the allowances, and the soil conditions in writing before you commit. That’s how Tom has run this company since 1998.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Leander and the north Austin metro.