# Garage Conversion & ADU in Lakeway, TX: 2026 Cost Guide

By the Home Remodel Pro team · published 2026-10-09 · Garage Conversion & ADU, Lakeway

In Lakeway, converting an attached garage into finished living space typically runs $55,000–$95,000, and $95,000–$140,000 once you add a full kitchen and bathroom. A new detached ADU in the backyard is a different animal: budget $225,000–$425,000 depending on size, site access and finish level. This guide walks through what moves those numbers, how permitting and HOA review work on a Lakeway lot, and how long the whole thing takes from the first visit to the final inspection.

## What a Lakeway garage conversion or ADU actually costs

Price is driven by three things: how much of the space needs new systems, how far water and sewer have to travel, and whether you are working inside an existing shell or building a new one from the ground up. A garage conversion already has a slab, walls and a roof, which is why it lands well below a detached build.

The ranges below are what we see on Lakeway and Lake Travis-area lots. We confirm the number for your specific address after a site visit and design, then put it in a fixed-price contract before anyone picks up a hammer.

- Office, gym or flex room conversion — insulation, drywall, flooring, HVAC, electrical, replacing the garage door with a wall and windows: $55,000–$75,000
- Guest suite conversion with a full bathroom: $75,000–$95,000
- Full conversion ADU with a kitchen, bathroom, laundry and a separate exterior entry: $95,000–$140,000
- Detached ADU, 400–800 sq ft: $225,000–$425,000, roughly $300–$450 per square foot all-in
- Adding a replacement carport or parking pad after the garage is enclosed: $12,000–$30,000

## What pushes your number up or down the range

Two Lakeway houses a street apart can price $40,000 apart. Here is what actually causes that spread, in rough order of impact.

- Plumbing distance. A bathroom or kitchenette that sits close to an existing wet wall is straightforward. Running new drain lines across a slab, or trenching 60 feet to a detached unit, adds $8,000–$25,000 — and hill country rock is slow to trench.
- Septic vs. sewer. Many Lakeway-area properties are on on-site septic. Adding a bedroom or a second dwelling usually means a licensed designer evaluating the existing system and Travis County reviewing it. Budget $6,000–$30,000 if the system needs expansion or replacement, and expect that evaluation to happen early, not late.
- Slab height and drainage. Garage slabs are usually poured lower than the house and sloped to the door. Raising and leveling the floor, or managing water at the old door opening, runs $3,500–$12,000.
- HVAC. Extending the existing system is cheaper than a dedicated unit. A mini-split for a conversion runs $4,500–$9,000 installed; a separate system for a detached ADU runs $9,000–$16,000.
- Electrical capacity. Older Lakeway panels sometimes have no room for a new subpanel. A panel upgrade and new service feed runs $3,500–$9,000.
- Site access for detached builds. Steep, rocky lots with limited equipment access add $10,000–$40,000 in excavation, retaining and material handling. This is common on the lots that back to greenbelt or step down toward the lake.
- Finish level. Stock cabinets, LVP flooring and a tile shower sit at the bottom of the range. Custom cabinetry, stone counters and a tiled wet room push to the top.
- Windows and exterior work. Framing in the garage door opening with a stucco or stone-veneer finish that matches the house costs more than siding, but it is what keeps the front elevation from looking converted.

## Permits, HOA review and inspections in Lakeway

A Lakeway address is not an Austin address, and the paperwork is different. Most properties inside Lakeway city limits are permitted through the City of Lakeway, while on-site septic permitting and review sit with Travis County. Some addresses with a Lakeway or Austin mailing address are actually in unincorporated Travis County or another jurisdiction entirely. We confirm which office has jurisdiction over your parcel before we price the job, and we handle the submittals, the plan review comments and the inspection scheduling. We also handle City of Austin permits when a project falls inside their jurisdiction.

Whether a second dwelling is allowed on your lot, how many bedrooms your septic can serve, whether a wall can be removed or an opening widened, and what setbacks and impervious cover apply — those are determinations for the permit office with jurisdiction and, where framing or foundations change, a licensed engineer. We do not guess at them. We get the drawings in front of the right reviewer and build to what comes back approved.

Separately from the city, most Lakeway subdivisions have an HOA with an architectural review committee. Exterior changes — filling in a garage door, a new window on the street elevation, a detached structure, a new driveway or parking pad — generally need that committee's approval, and their review calendar runs on its own schedule. Start it the same week the design is finished. We prepare the elevations and site plan you need to submit.

Plan on these line items in your budget:

- Permit and plan review fees: typically $900–$3,500 for a conversion, $3,000–$9,000 for a detached ADU, depending on valuation and jurisdiction
- Engineering, when the scope calls for it: $1,500–$5,000
- Septic evaluation or redesign by a licensed designer: $1,200–$4,000, plus county review
- Survey or site plan, if you do not have a current one: $700–$2,000
- Inspections you should expect: foundation (detached builds), framing, rough electrical, rough plumbing, rough mechanical, insulation, and a final before anyone moves in

## A realistic timeline, week by week

Design and permitting happen before demolition. That is deliberate — the construction calendar we hand you is the one we build to, and it only works if the drawings are approved and the materials are selected before the first day of demo.

Here is the sequence from the first phone call to a finished space. Review periods and HOA calendars are outside our control, so treat those weeks as estimates, not promises.

- Week 1: Site visit. We measure, look at the panel, the water heater, the slab and the drainage, and talk through what you want the space to do.
- Weeks 2–5: Design and selections. Floor plan, elevations, cabinet and finish selections, and any engineering the scope requires. You get a fixed price in writing at the end of this stage.
- Weeks 4–8: HOA architectural review runs in parallel with permit submittal.
- Weeks 6–14: Plan review and permit issuance. Conversions move faster than detached builds; septic review adds time.
- Garage conversion construction: 8–14 weeks. A conversion with a full kitchen and bath is at the top of that band.
- Detached ADU construction: 5–8 months from the first excavation to the final inspection.
- Final: Inspections, punch list walkthrough, and your warranty paperwork.

## How our fixed-price design-build process works

We design it, we price it, and our own carpenters build it. One contract, one schedule, one company responsible when something needs to be fixed.

Before work starts you get a fixed price in writing — not an allowance-heavy estimate that drifts for four months. The selections are made during design, so the cabinets, tile, fixtures and flooring in the contract are the ones that get installed. The only thing that changes the number is a change you ask for, or something the permit office requires after review, and either one gets priced and signed before we proceed.

Our carpenters are in-house, not subcontracted crews rotating through. Workmanship carries a 5-year warranty. We pull the permits and meet the inspectors. Financing is available if you would rather not pull the full amount out of savings.

When you are comparing contractors in Lakeway, ask every one of them the same questions:

- Which office has jurisdiction over my address, and who submits the permit application?
- Is my property on septic, and who evaluates whether the system can serve this scope?
- Is this a fixed price or an estimate with allowances? Which items are allowances, and what happens when they are exceeded?
- Who physically does the framing, trim and cabinet installation — your employees or a subcontractor?
- What is the warranty on workmanship, in writing, and how long?
- What does the schedule look like week by week, and what happens to it if plan review comes back with comments?
- Will you prepare the elevations and site plan my HOA committee needs?

## What to do next

Pull two things together before you call anyone: a recent survey or plat if you have one, and your HOA's architectural guidelines. Those two documents answer most of the early questions about where a detached unit could sit and what the exterior has to look like.

Then decide what the space is actually for. A home office and a rentable unit are two very different budgets, because the second one needs a kitchen, a bathroom, laundry, a separate entry and — on a septic property — a county review. Being honest about that on day one keeps the design from getting redrawn twice.

Book a site visit and we will walk the garage or the backyard with you, flag the cost drivers specific to your lot, and tell you which jurisdiction you are in. Design and selections follow, then a fixed price in writing, then we build.

## Lakeway homeowners also ask

### Can I put a detached ADU on my Lakeway lot?

That depends on your lot's zoning, setbacks, impervious cover, septic capacity and your HOA's rules — and those determinations belong to the permit office with jurisdiction over your parcel and, where septic is involved, Travis County. We confirm which office that is, prepare the drawings and handle the submittals. We will tell you what the reviewer says, not what we hope they will say.

### How much does it cost to turn a two-car garage into a guest suite in Lakeway?

A guest suite with a bedroom, full bathroom and no kitchen typically runs $75,000–$95,000. Add a kitchenette, laundry and a separate exterior entry and you are at $95,000–$140,000. The biggest swing factors are how far the plumbing has to run across the slab, whether the electrical panel has capacity, and whether your septic system needs attention.

### How long will my garage be out of commission?

Construction on a garage conversion runs 8 to 14 weeks, with the full-kitchen-and-bath versions at the top of that band. Before that, allow roughly 4 to 12 weeks for design, HOA architectural review and permitting, which run partly in parallel. We do not start demolition until the permit is issued and the selections are locked.

### Will enclosing the garage hurt resale value in Lakeway?

It depends on whether you replace the covered parking. In a neighborhood where every house has an enclosed garage, a conversion with no replacement parking reads as a loss to buyers. A carport or parking pad with a matching finish runs $12,000–$30,000 and keeps the elevation consistent. Matching the exterior — same stucco or stone, windows proportioned like the rest of the house — matters just as much as what you do inside.

## Check it with Lakeway's own pages

Permit rules and fees change, and the office that issues the permit is the authority on them, not this guide.

- [City of Lakeway — Building & Development Services, applications](https://www.lakeway-tx.gov/1165/Applications-Fees)

What a garage conversion or ADU in Austin involves: https://www.homeremodelpro.com/austin/garage-conversion-adu

## Get a free estimate

- Call (512) 601-5666 (Monday to Friday 8am–6pm and Saturday 9am–2pm); a project consultant calls back within one business hour.
- Request an estimate online: https://www.homeremodelpro.com/austin#quote
- 5-year workmanship warranty · one fixed price in writing · in-house carpenters · permits and inspections included

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Source: https://www.homeremodelpro.com/austin/blog/garage-conversion-and-adu-lakeway-guide · Home Remodel Pro Austin, TX