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 Brushy Creek
Adding square footage or building an ADU in Brushy Creek runs $45,000 to $130,000 for most additions, and $90,000 to $220,000 for a detached ADU. Those are the numbers we write into contracts for homeowners across the 78717 ZIP. The bigger piece most people learn the hard way: Brushy Creek is unincorporated Williamson County, so permits don’t go through a city building department like they do in Cedar Park or Round Rock. They go straight to the county, and the inspectors cover a huge territory. If you’ve been burned by a contractor who promised city-style timelines and then stalled at inspection, that’s the exact failure we prevent. Call Barrett & Sons at (877) 610-1318 and we’ll walk you through what actually happens here, not what works somewhere else.
Why Barrett & Sons Construction Is Brushy Creek’s Preferred Home Additions & ADU Company
Tom Barrett founded this company in 1998 and his sons run the crews. When we say we know Brushy Creek, we mean we’ve pulled Williamson County permits for additions on Streets like Great Oaks Drive, worked inside the Brushy Creek North subdivision, and sat through HOA architectural review meetings with homeowners who were worried about their builder warranty. The county inspection schedule is not a surprise to us. We plan rough-in and framing inspections three to four weeks out because we know the inspectors are covering rural and suburban territory across a wide county. An out-of-area contractor who assumes Austin timelines is going to stall. We don’t.
Every job includes a written scope, written allowances, and written change orders before anything changes price. Tom publishes his name, address, and license number, and a live person answers the phone 24/7. If something isn’t done right, the 90-Day Done Right Promise means one call brings Tom back. That’s not a guarantee buried in fine print. It’s written on every contract.
Our Home Additions & ADU Services in Brushy Creek
We offer the full Home Additions & ADU scope across Brushy Creek, but these four services come up most often in the 78717 housing stock. Most homes were built between 1993 and 2008, which means original finishes are aging out and families are deciding between moving and making the house fit them.
ADU Design & Permitting
This is where the unincorporated county reality matters most. A detached ADU in Brushy Creek needs a Williamson County permit, a site plan, and in many of the master-planned pockets like Brushy Creek North, HOA architectural approval before the county will even look at it. We handle the sequence correctly the first time. We’ve seen unapproved ADUs hit with stop-work orders because the HOA rules got skipped. That’s an expensive way to learn the process.
Garage Conversion ADU
Converting an attached garage is typically the most cost-effective ADU route in Brushy Creek, running $30,000 to $80,000 depending on whether you’re adding a bathroom, how much the slab needs leveling, and whether the existing walls meet current insulation codes. Older two-story brick-veneer homes from the late ’90s often have garage slabs with hairline cracks from clay movement. We inspect that before we commit to a number.
New Detached ADU
Detached ADUs on Brushy Creek lots are the high end: $90,000 to $220,000. The price gap comes from foundation type, utility trenching, and the county’s setback and impervious-cover requirements. On post-tension slabs over Blackland Prairie clay, we order a slab elevation survey before any structural work. That’s a Williamson County expectation on larger additions, and it catches problems that generic builders miss.
Junior ADU & Interior Conversion
For a smaller footprint, a junior ADU or interior conversion often uses existing square footage with a separate entrance, a small kitchenette, and its own bath. In Brushy Creek, this route usually lands between $45,000 and $90,000. It’s a good fit for aging relatives or a quiet rental income. The permitting path is still county-level, but the inspection count is lower, which helps the timeline.
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 Brushy Creek
We install brands you can look up, not mystery materials off a van. For Brushy Creek additions and ADUs, we regularly specify Simonton windows, Ply Gem siding and trim, and PGT impact-rated products when the exposure or HOA rules call for them. Carrying named brands means you can check the spec sheet yourself, and it means we can order replacement parts fast when something arrives short. That matters when a county inspection is already on the calendar and a missing window flange can cost you two weeks.
Common Home Additions & ADU Problems We See in Brushy Creek Homes
- Assuming Austin city permit processes apply. Brushy Creek jobs go through Williamson County, not the city of Austin. Contractors who don’t know the county stall at inspection scheduling, and you pay for the delay. We schedule staged inspections weeks ahead because we know how the county works.
- Adding a second story without mapping the post-tension slab first. The Blackland Prairie clay under Brushy Creek expands and contracts through drought-to-deluge cycles. A slab that has already shifted can make a new load path fail. We require a slab elevation survey before structural work on any second story addition.
- Skipping HOA architectural review. Neighborhoods like Brushy Creek North enforce exterior finish and setback rules. An unapproved ADU or a roofline that doesn’t match the master-planned aesthetic can trigger a stop-work order. We submit the design review package before we pull the county permit, in the right order.
- Builder warranty voidance from unpermitted structural changes. Most 1990s and 2000s homes in Brushy Creek are well past their original builder warranty on finishes, but some structural warranties transfer. Cutting into a load-bearing wall without a county-permitted change order can void what’s left. We keep every structural alteration on paper and permitted.
Pricing for Home Additions & ADU in Brushy Creek, TX
Here’s what you should expect to budget in Brushy Creek. These are line-item ranges we’ve written into actual contracts for homes in the 78717 ZIP, and they assume county permits, mid-grade to premium finish selections, and normal site conditions. If your lot has severe slab movement, buried utility conflicts, or a long trenching run to the alley, the number moves toward the upper end.
| Service | Brushy Creek Price Range |
|---|---|
| Home Addition | $45,000 - $130,000 |
| ADU Construction | $90,000 - $220,000 |
| Garage Conversion | $30,000 - $80,000 |
| Kitchen Remodel | $14,000 - $45,000 |
| Bathroom Remodel | $9,000 - $28,000 |
Every scope, every allowance, every price change arrives as a written change order before work happens. An allowance that isn’t on paper is a surprise waiting for a date. Call (877) 610-1318 and we’ll put your number on paper.
We Also Serve Cities Near Brushy Creek
Our crews work throughout Williamson County and the near north Austin suburbs. Homeowners in Brushy Creek often ask if we cover Anderson Mill, Jollyville, Cedar Park, and Wells Branch. We do, and the same written-scope and written-change-order rules apply everywhere we work. No surprise invoices at the end.
Serving Brushy Creek, TX - Our Local Coverage Area
We’re based in the Brushy Creek 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 Brushy Creek
Yes. Brushy Creek is unincorporated, so there is no city building department. Attached garage conversions to ADUs require a Williamson County permit, including approvals for plumbing, electrical, and any structural changes to the wall between the garage and the main house. We pull those permits directly with the county and schedule rough-in inspections with enough lead time to match the county inspectors’ wide coverage area. Call (877) 610-1318 for a free estimate and we’ll outline your specific permit sequence.
Most 1990s homes in Brushy Creek are past their original builder warranty on finishes, but any remaining structural warranty can survive a second story addition if the work is permitted through Williamson County and the structural changes are documented with county inspections. We protect that by pulling permits on every structural alteration and issuing written change orders for every scope change. If a warranty claim ever comes up, the paper trail supports you. Call (877) 610-1318 and we’ll review your warranty documents before any design work starts.
The Blackland Prairie clay under most of the 78717 ZIP shrinks and heaves seasonally, which is why many Brushy Creek slabs are post-tension. Before adding a room, we order a slab elevation survey to map current movement and crack patterns. If the slab has shifted, the new load path needs engineering adjustments or the addition can worsen existing cracking. This is a county-level expectation for larger additions, and we never skip it. Call (877) 610-1318 to schedule a site evaluation.
Neighborhoods like Brushy Creek North require architectural review before a detached ADU can be built, covering exterior finish, setback, height, and sometimes roofline matching. The HOA approval must come before the Williamson County permit in most cases. We submit the design package in the correct order and sit through the review with you if needed. Call (877) 610-1318 and we’ll help you read your HOA’s architectural guidelines first.
Attached garage conversions in Brushy Creek typically run $30,000 to $80,000. That range includes the county permit, electrical and plumbing rough-in, insulation, drywall, flooring, a bathroom if planned, and finish carpentry. The spread comes from the condition of the garage slab, whether you need a separate electrical subpanel, and how much of the existing structure meets current code. Call (877) 610-1318 for an exact quote. Estimates are free, and every line is in writing before you sign anything.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Brushy Creek since 1998.