A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateFast, Reliable ADU Builders Across San Antonio
Adding a detached ADU or JADU on San Antonio acreage usually costs $180,000 to $420,000 for a site-built unit, while prefab installations from brands like Abodu or Plant Prefab typically run $150,000 to $320,000 depending on size, site prep, and septic work. The biggest variable on larger lots isn’t the structure itself, it’s what’s under the ground and which jurisdiction reviews your plans. Benson ADU San Antonio has built across the city’s patchwork of incorporated limits and Bexar County ETJ, so we know before we quote whether you’re dealing with city setback rules or county well and septic requirements. Call (430) 258-2928 and we’ll walk your specific address through that first filter.
Why Benson ADU San Antonio Is San Antonio’s Preferred ADU Builders Company
Most San Antonio homeowners we meet don’t realize their street address can sit in one permitting world while a neighbor three doors down sits in another. That split, between San Antonio city limits and the Bexar County extraterritorial jurisdiction, changes everything about how an ADU gets designed, permitted, and priced. Our team has worked both sides of that line enough times that we flag it in the first conversation, not the third inspection. Troy Eastman set up this operation to handle exactly these acreage scenarios, where a project isn’t just a build, it’s a land-use puzzle.
We’re part of the Relay Home Co. family, founded in 2006, and every project carries The Relay Visibility Guarantee. That means a written price before any work starts, a 365-Day Done Right Promise, a written guarantee on the full project, and a free second visit if any covered repair fails. On a detached ADU with a county septic system off Bulverde Road or a JADU tucked behind a ranch-style house in Schertz, that written certainty is the only thing standing between you and a quote that drifts upward by the week.
Our ADU Builders crew arrives background-checked and in uniform. You get a live person when you call, not a voicemail loop. And you get named products, not a take-it-or-leave-it material list. We’re authorized to build with Abodu, Plant Prefab, and James Hardie cladding, so you can research the exact model in your quote the same night we send it.
Detached ADU in San Antonio
A Detached ADU in San Antonio on a larger lot means a standalone unit with its own foundation, utility connections, and often its own septic field if the property sits outside city sewer service. On acreage in the ETJ around Loop 1604, we’re not just framing walls, we’re grading a pad, routing a driveway long enough for concrete and lumber deliveries, and keeping the structure clear of well heads and drain fields. Site-built detached ADUs on San Antonio acreage typically run $220,000 to $420,000. Prefab or panelized units from Plant Prefab or Abodu run lower, often $160,000 to $280,000 once site work and septic are included.
County-Permitted Septic and Well Setbacks
Bexar County requires specific horizontal separation between a new septic system and an existing well. We’ve set slabs 40 feet or more from a well head on county land, because redrawing a plan mid-permit after you’ve already poured is the single most expensive mistake on an acreage ADU. We confirm your water source, soil type, and drain field location before we quote, so the price you see is the price you’re building from.
Long Haul Logistics and Equipment Access
On a 1.2-acre lot off Bulverde Road in the San Antonio ETJ, our crew framed a 750 sq ft detached ADU with a county-permitted aerobic septic system. The county road couldn’t take a full semi, so we hauled steel and trusses from our supplier off Loop 1604 in smaller loads almost daily. That’s the kind of line item a verbal estimate never mentions, and it can add $8,000 to $15,000 in logistics if it isn’t scoped up front. We scope it.
JADU in San Antonio
A JADU in San Antonio is a junior accessory dwelling unit, almost always a conversion within an existing home’s footprint: a garage, a large bedroom, or part of a first floor turned into a compact independent living space with its own kitchenette and bath. On San Antonio acreage, JADUs make sense because they usually dodge the septic and grading questions that drive detached ADU costs upward. You’re retrofitting conditioned space instead of creating new impervious cover. Typical JADU conversions in San Antonio run $90,000 to $180,000 depending on whether you need a new exterior entrance, a kitchenette rough-in, or upgraded electrical.
Garage and Bonus Room Conversions
The classic San Antonio JADU starts as an attached two-car garage or an oversized bonus room that never gets used. We frame the interior, run dedicated circuits, add a compact bath, and give the unit its own entry so it works as a rental or a space for aging parents. Because you’re not disturbing the lot, you skip the county septic process entirely, which shortens the permit path even when the property sits in the ETJ.
Utility Runs Through Existing Walls
One cost driver on JADUs in older San Antonio homes is the electrical panel. A 1970s ranch in the county often has a 100-amp panel that won’t carry a second kitchenette and a mini-split. We include that panel upgrade in the written price when the site visit shows it’s needed, instead of discovering it mid-rough-in and sending a change order.
Trusted Brands We Service in San Antonio
Benson ADU San Antonio is authorized to build with Abodu, Plant Prefab, and James Hardie materials. That matters on San Antonio acreage because prefab units arrive as engineered panel systems that go up far faster than stick-built framing, which shortens the window for weather exposure and reduces the number of material hauls down your county road. We also work with Tuff Shed for permitted accessory structures when the scope calls for a finished workspace rather than a dwelling. You research the brand, confirm the specs, and still get our written price before work starts.
Common ADU Builders Problems We See in San Antonio Homes
- City-versus-county confusion. San Antonio’s city limits wrap around unincorporated pockets and ETJ land, and two addresses a mile apart can fall under completely different permitting regimes. Homeowners start a project assuming city setbacks, then discover mid-design that Bexar County septic and well rules now govern the plan.
- Caliche and clay shifting under the slab. San Antonio’s clay soils expand when wet and contract in drought, and caliche layers make compaction uneven. A pad that isn’t properly moisture-tested and compacted can move within the first wet season, cracking the slab or binding door frames.
- Hidden delivery and access costs. Long driveways and narrow county roads often can’t take a full concrete truck or semi trailer. Without a haul check before quoting, the homeowner absorbs multiple smaller deliveries and extended pump time, sometimes thousands above the initial number.
- Septic and well setbacks missed early. On raw land in the ETJ, the septic drain field and existing well set the buildable envelope, not the fence line. Start the design before locating those, and you’ll redraw the whole site plan after soil testing.
Pricing for ADU Builders in San Antonio, TX
A detached ADU in San Antonio typically runs $180,000 to $420,000 site-built, and $150,000 to $320,000 prefab, with the gap driven by septic installation, grading, and material haul distances. JADU conversions land between $90,000 and $180,000 because they reuse existing structure and utilities. On acreage outside Loop 1604, expect $12,000 to $28,000 for a county aerobic septic system, and $6,000 to $18,000 for pad grading and drainage on clay soil. Every Benson quote includes those line items before you sign. Call (430) 258-2928 for a written estimate on your specific lot.
We Also Serve Cities Near San Antonio
Our crews run projects across the San Antonio metro, including San Antonio plus Converse, Universal City, Schertz, and Bulverde. If your land sits near one of those city limits, we’ll verify the exact jurisdiction before quoting, because county boundaries shift the permit path and the price.
Serving San Antonio, TX - Our Local Coverage Area
We’re based in the San Antonio 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 About ADU Builders in San Antonio
San Antonio city permits enforce city zoning setbacks, building codes, and water/sewer connection rules, while Bexar County permits for ETJ land add septic system design, well separation, and drainage review. The plan set changes materially between the two, and starting under the wrong assumption can cost you weeks and a redrawn site plan. Call (430) 258-2928 and we’ll check your address first.
Bexar County requires specific horizontal separation distances between a septic drain field and an existing well, typically a minimum of 40 feet for a new system, depending on soil type and well depth. Our crew has kept slabs 40 feet from well heads on county land, and we confirm your separation before we draw anything.
Clay expands when wet and shrinks in drought, and caliche layers make compaction inconsistent, so a poorly prepared pad can shift and crack the slab within the first wet season. We specify moisture-conditioned fill, deeper compaction, and surface drains that move water away from the foundation, which adds cost but prevents structural movement.
Yes, prefab and panelized units like Abodu can be permitted on ETJ land in Bexar County, provided the site plan meets county septic, well, and setback standards. The unit itself is engineered, but the county cares about the land under it, so grading, access, and utilities still need a full permit package.
Expect $8,000 to $15,000 in additional delivery and equipment logistics when a county road can’t take a full semi or concrete truck. That covers smaller staged loads, extended pump time, and sometimes a material laydown yard closer to the highway. We run that haul check before quoting so the number lands in your written price, not a change order.
If you’re weighing a detached ADU or JADU on San Antonio acreage, we’ll tell you which jurisdiction governs your address, what the septic and setback picture looks like, and what the build will actually cost in writing. Call Benson ADU San Antonio at (430) 258-2928 to schedule your free estimate.
Written by Troy Eastman, Owner at Benson ADU San Antonio, serving the San Antonio metro and surrounding counties.
