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ADU construction in San Antonio typically costs between $90,000 and $220,000 for a complete unit, with most homeowners spending around $150,000 for a standard one-bedroom accessory dwelling unit of roughly 600 to 800 square feet. Detached units with full kitchens and bathrooms land on the higher end of that range, while garage conversions and smaller studio layouts can come in closer to $90,000. These figures reflect the San Antonio market as of 2026, including materials, labor, permits, and utility connections.
Before you call around for quotes, it helps to understand exactly where that money goes. Below we break down the real line-item costs, what drives pricing up or down in Bexar County specifically, and how to avoid the most common budget surprises we see on ADU projects across the city.
Key Takeaways:
- Full ADU construction in San Antonio runs $90,000 – $220,000 in 2026, with $150,000 as a realistic midpoint for a one-bedroom unit.
- Detached ADUs cost 30 – 50% more per square foot than garage conversions.
- San Antonio’s permitting process, soil conditions, and HVAC requirements all affect final pricing.
- Mason Remodeling Co San Antonio provides a written price before any work begins, so you’ll know your exact number before a single tool is unpacked.
ADU Construction Cost Breakdown (2026)
Here is what a typical San Antonio ADU budget looks like, item by item. These are real working numbers from projects across the city, from Alamo Heights to Stone Oak to the near West Side.
| Cost Component | Typical Range (San Antonio, 2026) |
|---|---|
| Site preparation and foundation | $8,000 – $22,000 |
| Framing and structural work | $18,000 – $40,000 |
| Roofing (materials and labor) | $6,000 – $15,000 |
| Plumbing rough-in and fixtures | $8,000 – $18,000 |
| Electrical rough-in and panel work | $7,000 – $16,000 |
| HVAC (mini-split or tied to main system) | $4,000 – $10,000 |
| Insulation and drywall | $5,000 – $12,000 |
| Flooring | $3,000 – $8,000 |
| Kitchenette or full kitchen | $8,000 – $25,000 |
| Bathroom (full or three-quarter) | $9,000 – $28,000 |
| Windows and doors | $4,000 – $10,000 |
| Interior trim, paint, and finishes | $4,000 – $12,000 |
| Permits, plans, and engineering | $6,000 – $14,000 |
That totals roughly $90,000 on the low end and $230,000 on the high end, which matches the overall project range we gave above. The single biggest swing factor is whether you’re building a detached structure from the ground up or converting existing square footage like a garage or workshop.
A detached ADU requires a new foundation, full utility trenching from the main house or street, and standalone HVAC. That foundation work alone adds serious cost because San Antonio’s expansive clay soils shift with moisture levels, so engineers often spec pier-and-beam or post-tension slab designs rather than a simple floating slab. A garage conversion, on the other hand, already has a slab, walls, and a roof. You’re essentially reworking the interior, which is why ADU construction in San Antonio projects that start as garage conversions often land between $90,000 and $140,000 while ground-up detached units frequently push past $180,000.
What Affects ADU Construction Pricing in San Antonio
Every ADU quote you receive will differ, sometimes by tens of thousands of dollars. Here are the factors that actually move the number in San Antonio, based on what we see on job sites across the city every week.
- Detached vs. attached vs. garage conversion. A detached ADU needs its own foundation, utility runs, and roof, which adds $40,000 – $70,000 compared to converting an attached garage or adding a second-story bump-out. This is the single largest pricing variable in San Antonio.
- Soil conditions and foundation type. Much of San Antonio sits on expansive clay. Depending on your lot’s soil report, you may need a pier-and-beam foundation or additional grading, which can add $5,000 – $15,000 to the total. Builders who skip this step end up with cracked slabs and warranty claims, and we’ll simply tell you up front if your soil requires it.
- Utility runs and connection fees. If your ADU sits more than 50 feet from the main electrical panel, water line, or sewer tap, costs climb quickly. Trenching and new service drops can run $3,000 – $10,000 depending on distance, soil, and whether CPS Energy or SAWS requires a new meter.
- Kitchen and bathroom scope. A kitchenette with a mini-fridge, microwave, and small sink keeps costs down. A full kitchen with a range, dishwasher, and custom cabinetry can add $15,000 – $25,000. A full bathroom with a walk-in shower runs more than a three-quarter bath with a corner stall. These choices alone swing your total by $20,000 – $40,000.
- HVAC approach. A ductless mini-split system costs $4,000 – $7,000 installed and works well for smaller ADUs. If you tie into the main home’s central system, you’ll need bigger equipment and longer duct runs, which can push costs to $8,000 – $12,000 and may require replacing the main unit entirely.
- Permitting timeline and plan requirements. The City of San Antonio’s Development Services Department requires stamped architectural plans, a site plan showing setbacks, and in many cases a tree survey if you have mature oaks or pecans on the lot. Plan preparation and permit fees frequently fall between $6,000 and $14,000, and the review timeline can stretch from 6 to 16 weeks depending on workload.
San Antonio-Specific Costs You Should Know About
Some costs are unique to this market, and most homeowners don’t learn about them until they’re already mid-project. Here are the ones that catch people off guard.
SAWS impact fees. San Antonio Water System charges tap and impact fees for any new dwelling unit, including ADUs. These fees run from $2,500 to $6,000 depending on meter size and location, and they’re billed separately from your construction costs. If your ADU shares the main house’s water line, you may avoid a new meter, but SAWS still requires an inspection and possibly a line upgrade if the existing service is undersized.
CPS Energy service requirements. A detached ADU almost always needs its own electrical panel and possibly a second meter. CPS Energy charges for the service drop, meter base, and inspection, typically adding $1,500 – $4,000. If your existing panel doesn’t have capacity, which is common in homes built before 1990 in neighborhoods like Jefferson and Beacon Hill, you’ll need a main panel upgrade at $3,000 – $6,000 before the ADU panel can be fed.
Tree protection ordinances. San Antonio protects heritage trees, which include mature live oaks, pecans, and cypress trees meeting certain size thresholds. If your ADU site is within a protected tree’s critical root zone, you’ll need a tree survey and possibly a root-protection plan. This can add $1,000 – $3,000 in consulting and mitigation costs, and in rare cases, force you to reposition the ADU footprint entirely.
Floodplain considerations. Parts of San Antonio, particularly near Leon Creek, Salado Creek, and the San Antonio River, sit within FEMA-designated flood zones. If your lot is in a floodplain, you’ll need elevation certification and possibly a raised foundation, adding $8,000 – $20,000. Check your FEMA map early in the process so there are no surprises after plans are drawn.
How to Save on ADU Construction
Saving money on an ADU doesn’t mean cutting corners. It means making informed decisions before the first shovel goes in the ground. Here’s what actually works in San Antonio.
Convert before you build. If you have an attached or detached garage, a conversion almost always costs less per square foot than new construction. You’re reusing the slab, framing, and roof, which saves $30,000 – $60,000 on a typical San Antonio lot. The trade-off is ceiling height and layout flexibility, but for a rental unit or a space for aging parents, a garage conversion at $100,000 often makes more sense than a ground-up build at $180,000.
Keep the footprint simple. Every corner, bump-out, and custom roofline adds framing complexity, which adds labor hours. A simple rectangular footprint with a gable roof is the cheapest shape to build. Complex roof lines and angled walls can push framing costs up 20 – 30% in San Antonio’s market.
Choose finishes that match the neighborhood, not a magazine. You don’t need Cambria countertops and Grohe fixtures in a rental ADU. Solid mid-grade materials perform well for years and keep you on budget. Save the premium finishes for the main house. We’ll spec materials that hold up to San Antonio’s heat and humidity without overspending, and our specification-grade partnerships mean you can upgrade selectively if you choose to.
Bundle the ADU with other work. If you’re already planning a roof replacement or a main panel upgrade, doing it at the same time as the ADU construction saves on mobilization costs and sometimes permit fees. One contractor managing the whole home project also means one written price, one schedule, and one guarantee covering everything.
Get a written price before you commit. Vague verbal estimates are how budgets get blown. Mason Remodeling Co San Antonio delivers a written price before any work starts, on every project, every time. You’ll know exactly what the ADU costs before we order materials or schedule the first crew. Call (254) 269-5071 for a free estimate, and we’ll walk you through which options fit your budget.
Why ADU Costs in San Antonio Are Rising
If you priced an ADU two or three years ago and are revisiting the project now, you’ll notice the numbers have moved. That’s not your imagination, and it’s not a contractor markup trick. Here’s what’s happening in this market specifically.
Concrete and rebar pricing. San Antonio’s construction boom, driven by continued population growth along the I-35 corridor and the 1604 loop, has kept concrete plants running at capacity. Concrete costs here have risen faster than the national average because local demand is so consistent. A yard of concrete that cost $125 delivered in 2021 now runs $160 – $185 depending on the mix and the plant’s location.
Labor availability. The San Antonio construction labor pool is stretched thin by large commercial projects downtown, the continued expansion around Brooks City Base, and residential development in far west and northeast Bexar County. Skilled framing crews and electricians command premium rates, and that flows directly into ADU pricing. Crews that charge $65 an hour in 2022 now bill $85 – $95.
Permit and impact fee increases. The City of San Antonio has raised development services fees multiple times since 2023, and SAWS and CPS Energy have both adjusted their connection charges upward. A permit package that cost $4,500 in 2022 may run $7,000 or more in 2026. These are fixed costs no contractor can absorb or waive.
This is exactly why we put the price in writing before any work starts. When a contractor gives you a loose verbal range and starts buying materials later, those increases land on your final invoice. With Mason Remodeling, your price is your price. If material costs rise after we’ve given you a written number, that’s our risk to manage, not yours.
Who Is Coming to Your Property
An ADU project means weeks of work at your home, with multiple tradespeople coming and going. You should know exactly who you’re opening the door to, every time.
Mason Remodeling follows what we call the Threshold Standard. Every technician and crew member is background-checked and identity-verified before they ever set foot on your property. Before any visit, you receive the technician’s name and photo so you know who to expect. On arrival, they’re in a clean, marked uniform and they hand you a photo ID badge at the door.
This matters more than most homeowners realize. An ADU project involves electricians pulling wire inside your home’s walls, plumbers working under your house and around your main lines, and crews moving through common spaces for weeks. You shouldn’t have to wonder whether the person in your backyard is supposed to be there. With us, you’ll always know.
Isaac Pruett leads the Mason Remodeling Co San Antonio team, and the entire operation runs on a simple principle: a homeowner should never have to gamble on who shows up. If you’re home alone during the day, if you have young children, or if you simply want certainty about the people around your house, this is what we do differently from most contractors in San Antonio.
FAQs – ADU Construction Cost
How much does it cost to build a 600 sq ft ADU in San Antonio?
A 600-square-foot ADU in San Antonio typically costs $120,000 to $180,000 for a detached unit with a full bathroom and kitchenette. At $200 to $300 per square foot, this is the sweet spot for rental-ready units. A garage conversion of the same size can come in closer to $95,000 – $130,000 depending on the condition of the existing structure. Call (254) 269-5071 and we’ll give you a written number for your specific lot and scope.
Is it cheaper to build an ADU or convert a garage in San Antonio?
A garage conversion is almost always cheaper, typically running $90,000 to $140,000 versus $150,000 to $220,000 for a new detached ADU of similar size. The existing slab, walls, and roof eliminate $30,000 – $60,000 in foundation, framing, and roofing costs. The trade-off is design flexibility and often lower ceiling heights. For a free cost comparison between converting your garage and building new, call (254) 269-5071.
How much does a two-bedroom ADU cost in San Antonio?
A two-bedroom ADU in San Antonio typically costs $180,000 to $250,000 for a detached build of 800 to 1,000 square feet. The second bedroom adds roughly $30,000 – $50,000 over a one-bedroom unit because of added framing, finishes, larger HVAC requirements, and often a larger foundation. Two-bedroom ADUs also trigger higher SAWS impact fees in some cases. Get an exact quote by calling (254) 269-5071.
Do I need a permit to build an ADU in San Antonio?
Yes. San Antonio requires building permits, plan review, and inspections for any ADU with plumbing or electrical systems, and most ADUs also need a separate SAWS water connection review and CPS Energy approval. Permit and plan costs typically run $6,000 to $14,000 for a standard detached ADU in 2026. Our team handles the full permitting process so you don’t have to navigate Development Services on your own.
How long does ADU construction take in San Antonio?
A standard detached ADU in San Antonio takes 5 to 9 months from permit submission to final inspection, with 6 to 16 weeks of that spent in plan review and permitting before construction starts. Garage conversions move faster, typically 3 to 6 months total. Weather delays are common in spring and early summer when thunderstorms roll across Bexar County, so we build that buffer into our schedules up front. For a realistic timeline on your specific project, call (254) 269-5071.
Can I build an ADU in San Antonio for under $100,000?
It’s possible for a small garage conversion or a studio ADU under 400 square feet, but tight. Expect $85,000 to $100,000 for a basic studio conversion with a kitchenette and three-quarter bath. A ground-up detached ADU under $100,000 is rare in San Antonio in 2026 unless you’re using a pre-fabricated shell and doing significant finish work yourself. We’ll tell you honestly whether your budget works for what you want, and we’ll put that number in writing before you commit.
Get a Written Price Before You Decide
You don’t have to guess what your ADU will cost, and you shouldn’t have to. Mason Remodeling Co San Antonio delivers a written price before any work starts, on every project, every time. No verbal ranges that grow. No surprise invoices. No “we’ll figure it out as we go.”
We’ve been building in San Antonio since 2004 as part of the Threshold Group family of home-service companies, and our 365-Day Done Right Promise covers your ADU for a full year from the completion date. If something isn’t right within that year, we make it right at no cost to you. A free return visit is included if a repair fails, with no charge, no dispute process, and no conditions.
Call (254) 269-5071 for a free estimate. A live person answers, 24 hours a day, 7 days a week. You’ll get straight answers, real numbers, and a written price you can plan around.
Pricing reflects the San Antonio market as of 2026. Mason Remodeling Co San Antonio offers free estimates – call (254) 269-5071.
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