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Ameristar Home Additions & ADU: The San Antonio Owner’s Guide
An Ameristar home addition or ADU in San Antonio typically runs $45,000 to $130,000 installed, and most projects take 12 to 20 weeks depending on scope, foundation work, and utility connections. We are seeing a surge of owners in neighborhoods like Stone Oak, Alamo Ranch, and Terrell Hills discovering that their existing Ameristar product or extension was built years ago with materials that simply don’t hold up to South Texas heat and shifting clay soil. The wall assembly, roofline tie-in, or pier-and-beam underpinning is usually where the failure starts. That’s why we stock common Ameristar-compatible materials on our trucks and can diagnose the issue on the same visit. Sawyer Remodel San Antonio is an independent general contractor, not affiliated with Ameristar.
Key Takeaways
- Typical full Ameristar addition or ADU rebuild in San Antonio: $45,000 – $130,000.
- Doesn’t always require a full tear-down; see “repair vs replace” below.
- Clay soil expansion in San Antonio is the #1 cause of Ameristar addition failures we see.
- We give a written price before any work starts, under The Relay Visibility Guarantee.
Which Ameristar Models This Applies To
This covers the full range of Ameristar-built home additions, garage conversions, and accessory dwelling units common across Bexar County. You’ll find the model or plan number on a plate inside the main electrical panel door, on the original permit placard near the water heater, or stamped on the first floor joist in the crawl space or attic access. Knowing whether you have a slab-on-grade Ameristar addition versus a pier-and-beam setup matters: pier-and-beam homes shift independently of the main house, and that’s where we see cracks at the connection seam between the original structure and the addition.
When you’re weighing OEM Ameristar materials versus quality aftermarket equivalents, the honest answer is this: for structural lumber, sheathing, and roof underlayment, aftermarket brands that meet or exceed code are fine and often better priced. For things like windows, exterior trim profiles, and siding that need to match the existing look, OEM or exact-pattern duplication is worth the extra cost. We will tell you straight which is which on your project, and we document everything in the written quote so there are no surprises.
Styles & brands we work with
Signs Your Ameristar Home Addition & ADU Is Failing
- Cracking at the seam where the addition meets the main house. This is the classic symptom of differential settling. In San Antonio’s expansive clay soil, the addition’s foundation moves at a different rate than the original slab, and the drywall or exterior joint cracks first.
- Doors and windows in the addition that stick or won’t latch. The opening has gone out of square, which points to foundation movement or a compromised header. A door that sticks in summer but works in winter is a moisture-driven wood movement issue; a door that sticks year-round is structural.
- Sagging roofline where the addition ties into the original roof. This is a flashing and structural tie-in failure. Water pools at the transition, rots the framing, and the ridge line visibly dips.
- Musty smell or visible mold near the baseboards or under windows. The addition’s flashing or wall waterproofing has failed, and San Antonio’s humidity plus our hard rainstorms push moisture inside the wall cavity. Once you smell it, the rot is already behind the drywall.
- Floors that bounce or feel springy. Floor joists are undersized or have been compromised by moisture or termite damage. San Antonio is termite country, and older Ameristar additions with wood framing sitting close to grade are prime targets.
See the difference
Before
After
Before
After
Before
AfterReplacement Cost & What’s Included
The full rebuild of an Ameristar home addition or ADU in San Antonio lands between $45,000 and $130,000. The spread is wide because scope matters: a 400-square-foot bedroom addition on a clean slab with electric already pulled is a very different job than a full ADU with a kitchenette, bathroom, and separate utility drops. Here’s what moves the price:
- Addition size: $110 – $160 per square foot for a finished, heated and cooled space in San Antonio.
- Foundation work: Slab repair or new piers runs $8,000 – $25,000 depending on soil conditions and access.
- Bathroom or kitchenette inside the addition: $9,000 – $45,000 depending on fixtures and finishes.
- Roof tie-in and matching: $6,000 – $18,000 to match existing shingles or standing seam metal and properly flash the transition.
Every quote from us is a written line-by-line price before any work starts. You see the exact material cost, labor, permit fees, and the warranty terms printed in black and white. If it’s not done right, the 365-Day Done Right Promise covers it in writing for a full year after the job closes.
DIY or Call Us?
You can safely check a few things yourself: look for visible cracking at the floor-to-wall seams, run a level across door frames, and check for water staining on ceiling drywall. That information helps us diagnose faster when you call. What you should not do is attempt to jack and level a settled addition, re-flash a roof tie-in, or open a wall that shows mold without a containment plan. Those jobs can put you on a ladder over open framing, expose you to mold spores inside wall cavities, or leave a structural load unsupported if you remove framing incorrectly.
Luca Romano grew up in East Los Angeles, learned the trade at Los Angeles Trade-Technical College, and has spent decades running jobs like this across the Southwest. He still does a final walkthrough on every project in San Antonio, checking that the framing is square, the tile is level, and the roofline runs true. The craft comes first. Everything else follows.
If your Ameristar addition is showing any of those symptoms, call (432) 547-6806 and we’ll get eyes on it. The estimate is free, and it’s in writing.
FAQs
Most Ameristar additions in San Antonio, properly built, give you 30 to 50 years of service. The first things to fail are usually the roof tie-in flashing and window sealants, which can start degrading in 10 to 15 years under our UV exposure and humidity cycles. If the foundation wasn’t engineered for expansive clay soil, you can see structural settlement within the first 5 to 10 years. Call (432) 547-6806 and we’ll tell you exactly what’s failing and what it’ll cost to fix.
In our experience, about 70% of failing Ameristar additions in San Antonio can be repaired without a full tear-down. Cracking at the seam, door misalignment, and roof flashing leaks are usually fixable with foundation piers, re-shimming, and re-flashing. A full rebuild only makes sense when the framing is rotted past repair or the cost of piecemeal fixes exceeds 60% of new construction. We’ll give you the repair-versus-replace numbers side by side so you can decide with real information.
A full addition rebuild in San Antonio runs 12 to 20 weeks from permit approval to final inspection. Foundation and framing eat up most of that time, and the City of San Antonio’s inspection schedule paces the rest. We keep you informed at every step with photo updates before and after, and you always know exactly who is walking onto your property that day.
We stock the common structural materials on our trucks: pressure-treated sill plates, engineered LVL headers, galvanized flashing, and the sealants we use on every San Antonio job. For finish materials like siding, windows, and trim profiles that need to match your existing Ameristar addition, we order those to spec from our usual partners including KraftMaid, Cambria, and Silestone. That means no mystery suppliers and no weeklong delays while a parts counter guesses.
If you’re pricing an Ameristar addition or ADU in San Antonio, call (432) 547-6806 or stop by. We’ll walk the job with you, put the number in writing, and you’ll know exactly what it costs before you commit to anything.
Written by Luca Romano, Owner, Sawyer Remodel San Antonio at Sawyer Remodel San Antonio, serving San Antonio and nearby areas.
