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 an ADU in San Antonio typically costs between $95,000 and $240,000 for a detached one-bedroom unit, and most builds take 6 to 12 months from permit to final inspection. Our ADU Builders team handles every phase: site assessment, foundation work, framing, utility connections, and finish-out. We know which San Antonio neighborhoods trigger which code requirements, and we write every price down before the first tool leaves the truck. Call (210) 981-6358 to schedule your free estimate.
Why Seedling ADU San Antonio Is San Antonio’s Preferred ADU Builders Company
San Antonio homeowners keep telling us the same thing: they want an ADU without a construction site in their kitchen for nine months. That’s why every Seedling project starts with a written scope and price, and why our crews follow the Cedarwell Care Promise on every visit – shoe covers at the door, drop cloths wherever we walk, pet-safe products where there’s a choice, and a photo of the clean-up before the crew leaves. Ben Ortega leads our San Antonio team, and he holds every job to that standard personally.
We work across San Antonio daily, from Jefferson and Beacon Hill to Stone Oak, Alamo Ranch, and the far west side near Loop 1604. Homeowners in Universal City, Helotes, Cibolo, and Floresville call us too. The common thread: older homes with hidden conditions, or newer lots with expansive clay that shifts. We plan for both. A live person answers our phone 24/7 during an active build. No voicemail tree, no “we’ll call you back next business day.”
If you’re searching for ADU Builders in San Antonio, you’ve probably already noticed how many companies sell square footage. We sell something different: a price that doesn’t move, and a crew that treats your house like a home, not a job site. That’s the Seedling difference, and it’s backed by our 365-Day Done Right Promise – if it’s not done right, we make it right.
ADU Construction in San Antonio
ADU Construction in San Antonio means building a secondary dwelling on the same lot as your primary home – a detached backyard unit, a garage conversion, or an attached addition with its own entrance. Most San Antonio homeowners who call us have aging parents moving in, adult kids returning, or a rental income goal tied to the city’s rising property values. A typical one-bedroom ADU construction project in San Antonio runs $95,000 to $180,000; a two-bedroom unit with a full kitchen and laundry typically lands between $180,000 and $240,000.
Permit-Triggered Code Upgrades
When we connect a new ADU to an older San Antonio home, the permit triggers code upgrades on the existing structure. That’s not a surprise to us – it’s the plan. We inspect first, write allowances into your contract for the things we know are hiding behind original plaster, and any actual surprise gets priced and approved by you in writing before we touch it. Ben’s rule: no change order without a signature on the line item.
Working Around Your Family
ADU construction doesn’t pause your life. Our crews keep pathways clear, quiet tools near bedrooms during nap and school hours, and the site buttoned up every evening. You’ll get a photo of the clean-up before the crew leaves. Every day. That’s a Care Promise detail, not an upsell.
Detached ADU in San Antonio
A Detached ADU in San Antonio is a stand-alone structure in your backyard – typically 400 to 1,000 square feet – with its own foundation, utilities, and entrance. This is the most popular ADU type we build in San Antonio, partly because our city’s older neighborhoods still have the original alleys used for garage access. That means we can often design an alley-loaded detached ADU that faces the alley, preserving your front yard, your lawn, and the historic character of your street.
Alley-Loaded ADUs on Historic Lots
In neighborhoods like Jefferson and Beacon Hill, the alleys are intact and wide enough for a separate entry, a small patio, and utility access. This is a real San Antonio advantage – Austin’s alley network is far less consistent, so this layout is harder to pull off there. Here, it’s often the cleanest way to add a detached unit without tearing up the front setback or fighting the historic district guidelines on street-facing changes.
Foundation Planning on Clay Soils
Outer-ring San Antonio lots – Stone Oak, Alamo Ranch, the far northwest – sit on expansive clay that moves with moisture swings. A detached ADU slab needs a proper soil report and often a pier-and-beam or stiffened slab design. We coordinate that before we pour. Skipping it is how you get a cracked slab connection and a door that sticks within the first year. We’d rather do it right the first summer.
Trusted Brands We Service in San Antonio
Some San Antonio homeowners want a fully custom stick-built ADU. Others have already researched prefab and panelized options and just need a builder who can handle sitework, foundation, and assembly. We work with both paths. Our team has hands-on experience with Plant Prefab, Abodu, Tuff Shed, and James Hardie materials – brands serious ADU buyers often compare before calling anyone. We’ll walk you through what each option actually costs on your lot, not just the brochure price. If you’re leaning prefab, we’ll tell you honestly whether your site is a good candidate or whether a custom build makes more sense for the dimensions, setbacks, and soil conditions we’re dealing with.
Common ADU Builders Problems We See in San Antonio Homes
- Outdated wiring hidden behind original plaster. In early 20th-century bungalows across Jefferson and Beacon Hill, we regularly open walls to add structural connections for a new ADU and find knob-and-tube wiring that must be replaced to meet current code. Our estimates include a written allowance for this work so the number doesn’t move on you mid-project.
- Undersized roof framing with dry rot. San Antonio’s humid summers take a toll on older 2×4 rafters, especially where flashing has failed. When we tie a detached ADU roof into an existing structure, we often need to sister rafters with engineered lumber. That’s another line item we price before we start, not after.
- Expansive clay soil movement. Outer-ring tract homes built in the 1970s through 1990s sit on clay that heaves and shrinks. A poorly planned ADU slab can crack at the connection point within a year. We pull soil reports and design foundations to move with the ground, not against it.
- Edwards Aquifer recharge zone stormwater rules. Projects on the northwest side near the aquifer recharge zone face stricter drainage and runoff requirements. If your permit review catches inadequate stormwater management, you’re looking at a costly redesign. We factor those rules in from the first site visit, so there’s no stop-work surprise.
Pricing for ADU Builders in San Antonio, TX
Here’s what we tell every San Antonio homeowner who calls: a studio ADU (400-500 sq ft) typically runs $85,000 to $150,000. A one-bedroom detached unit runs $95,000 to $180,000. A two-bedroom unit with full kitchen, laundry, and separate HVAC runs $180,000 to $240,000. Garage conversions start around $75,000 for a simple studio and climb with the structural and utility work your specific garage demands. What moves the number: soil conditions, permit-triggered upgrades to the main house, foundation type, utility runs from the street or alley, and the finish level inside the unit. Every Seedling project gets a written price before any work starts, with allowances for the unknowns clearly spelled out. No lump-sum “we’ll figure it out later” language. Call (210) 981-6358 for an exact quote – estimates are free.
We Also Serve Cities Near San Antonio
Our crews serve San Antonio daily and take projects in the surrounding communities of Universal City, Helotes, Cibolo, and Floresville. If you’re inside the loop or in a neighboring city, the same written pricing, the same Care Promise, and the same 365-Day Done Right Promise apply. We schedule free estimates throughout the San Antonio metro area each week.
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
An alley-loaded lot usually saves you money and time, because we can bring utilities from the alley side instead of trenching through your front yard and driveway. On intact historic alleys in Jefferson and Beacon Hill, the savings often run $3,000 to $8,000 on utility work and reduce the timeline by two to four weeks. If your alley is unimproved or overgrown, we’ll need to negotiate access and possibly grade a temporary path, which adds cost. Call (210) 981-6358 and we’ll walk your specific lot with you.
Expect the electrical panel to be evaluated first – many pre-1960s San Antonio homes have 60-amp or 100-amp panels that can’t support an additional dwelling, so we often need a service upgrade to 200 amps. You’ll also likely trigger updates on wiring connected to the ADU (knob-and-tube replacement is common), smoke and CO detection, and sometimes seismic strapping on water heaters. These are predictable, and we write allowances for them into your upfront price. We don’t wait until the wall is open to tell you it’s coming.
Yes. If your San Antonio lot sits within the Edwards Aquifer recharge zone – common on the northwest side near I-10 and Loop 1604 – your ADU permit will likely require stormwater management features like rain gardens, permeable paving, or a detention system. This can add $4,000 to $12,000 to a project. We identify recharge-zone status on our first site visit and design for it before we submit plans, so the permit review doesn’t hand you a surprise drainage redesign.
Yes, but not with a standard slab. Expansive clay in outer-ring San Antonio lots moves significantly between wet and dry seasons, so we typically use a pier-and-beam foundation or a stiffened slab engineered for soil movement. This adds $6,000 to $15,000 compared to a conventional slab, depending on lot size and soil report findings. Skipping this step is how you get a cracked ADU connection and sticking doors in year one. We do it right from the pour.
We work with Plant Prefab, Abodu, Tuff Shed, and James Hardie materials, among others. A prefab ADU can shorten on-site construction time, but it doesn’t eliminate the foundation, utility, and sitework costs, which are San Antonio-specific. Ben will walk you through the real landed cost of Plant Prefab or Abodu on your lot versus a custom stick build, so you can compare honestly. Call (210) 981-6358 for exact pricing – estimates are free.
Written by Ben Ortega, Owner at Seedling ADU San Antonio, serving San Antonio and the surrounding metro area.
