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Toto Home Additions & ADU: The San Antonio Owner's Guide
A Toto home addition or ADU project in San Antonio typically runs $45,000 to $130,000 for the addition itself, with standalone ADU construction landing between $90,000 and $220,000 depending on square footage, foundation work, and finish level. We plan, permit, and build these projects from slab to trim, and we install Toto plumbing fixtures throughout so your new space matches the rest of the house. Most owners don't call us because the project failed. They call because the first contractor gave them a price that ballooned after demo.
That's the symptom picture we see in this part of Texas every month: homeowners with a half-finished addition, a permit that got flagged, or a quote that changed three times before a single footing was poured. Luca Romano has walked enough San Antonio job sites to know what happens when framing doesn't get squared or the plumbing rough-in gets ignored. He still does the final walkthrough on every project himself, because the handoff is the part of the work that matters most.
Which Toto Models This Applies To
If you're adding square footage or building an ADU, the Toto pieces that matter most are the ones that survive San Antonio's hard water and summer heat: the Drake and UltraMax toilets, the Aquia wall-hung line, and any Toto lavatory or shower fixture you're matching to existing plumbing. The compatibility gotcha most owners miss is the rough-in depth. A wall-hung Toto Aquia needs an in-wall carrier tank with a 2×6 wall depth minimum, which changes your framing before drywall ever goes up. Standard 12-inch rough-in floor-mounted Toto models fit typical 2×4 walls without issue, but if you're converting an exterior wall to interior in your addition, that dimension changes fast.
OEM Toto parts are what we spec first. The porcelain formulation and glazing on Toto's CEFIONTECT finish isn't something an aftermarket manufacturer replicates well, and in San Antonio's mineral-heavy water, cheaper equivalents show scale buildup in a year. For valves and fill mechanisms, quality aftermarket options from Korky or Fluidmaster work fine and cost less. For anything Toto-specific like the flush tower or the Aquia mounting studs, we stick with OEM. Sawyer Remodel San Antonio is an independent contractor, not affiliated with Toto, but we've installed enough of their fixtures to know which parts to match and which corners not to cut.
Styles & brands we work with
Signs Your Toto Home Additions & ADU Is Failing
- Framing out of square in the new addition. You shouldn't be able to see daylight through a corner or feel a bow in a stud wall. When a room is out of square by even an inch, every Toto fixture that gets installed later fights it: toilets rock, vanities sit crooked, tile lines drift. Fixing framing after drywall is a five-figure lesson.
- Plumbing rough-in set to the wrong depth. This is the one we see most in ADU conversions and garage-to-bedroom work in San Antonio. A floor-mounted Toto needs that 12-inch rough-in from finished wall to the center of the flange. If the rough-in is at 10 inches because someone framed the wall thick, the toilet doesn't fit and the fix means opening the slab or reframing the wall.
- Water pressure drops when more than one fixture runs. A 3/4-inch supply line that tees off to feed a new bathroom and the existing house will starve a Toto pressure-assist flush every time. In older San Antonio post-war homes on 1/2-inch galvanized lines, you'll notice it immediately: the toilet fills slow, the shower stutters, and nobody can run the washer while someone showers.
- Foundations not prepped for Texas clay soil. San Antonio sits on expansive clay that moves with every rain and drought cycle. A Toto fixture doesn't care about that. But the floor it sits on does. If your addition slab wasn't engineered with proper piers or post-tension cable, you'll see hairline cracks at door corners within two seasons, then a toilet that wobbles, then a wax ring that leaks into the subfloor.
- Permits never pulled or inspections skipped. The quiet failure. You find out when you go to sell and the buyer's inspector flags a window egress or a missing plumbing permit in San Antonio's permit portal. Then the Toto fixtures that work fine become part of a legal headache because the addition itself was never approved.
See the difference
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After
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After
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AfterReplacement Cost & What's Included
A full home addition in San Antonio runs $45,000 to $130,000. That range covers foundation, framing, roofing, electrical, plumbing, drywall, flooring, and finish work, with Toto fixtures spec'd into every bath or wet area. A standalone ADU with its own kitchenette and bath typically lands between $90,000 and $220,000, driven by square footage, site access, and whether you need a separate electrical service drop from CPS Energy. Garage conversions sit between $30,000 and $80,000, which is often the most budget-friendly way to add a Toto-outfitted bathroom and living space without new foundation work.
What's included with us is the same on every job: a written price before we start, a line-by-line breakdown so you see where every dollar goes, permits pulled and inspections passed, and our 365-Day Done Right Promise. If something isn't done right, we make it right. That's in writing, not a handshake.
Here's the honest math for the component parts of a Toto-heavy addition or ADU:
- Kitchen remodel within the addition: $14,000 – $45,000
- Bathroom remodel: $9,000 – $28,000
- Walk-in shower installation with Toto fixtures: $4,500 – $12,000
- Bathroom vanity installation: $800 – $3,000
- Countertop installation: $2,000 – $6,500
- Window replacement for the new space: $4,500 – $15,000
DIY or Call Us?
Swapping a Toto fill valve or flapper? A homeowner can handle that in an afternoon with a wrench and a YouTube video. We won't pretend otherwise. The rest of this work, the framing, the plumbing rough-in, the foundation, the electrical, is not DIY territory. One wrong move on a load-bearing wall or a mis-sized supply line turns a $45,000 addition into a $70,000 correction. We've fixed enough of those in San Antonio to say it plainly: if you're planning the build, plan to hire the build.
What you can do before calling anyone: check your lot's setback lines through the City of San Antonio Development Services portal, confirm your HOA rules if you have one, and write down what the new space has to do. Then call (432) 547-6806. We'll walk the site, talk through the Toto fixtures you want, and put a price in writing before anything gets torn apart.
FAQs
How long does a Toto-fitted home addition or ADU last in San Antonio? With proper foundation engineering for expansive clay soil and Toto fixtures installed to spec, an addition or ADU should last 50 years or more in San Antonio. The Toto fixtures themselves often outlive the building: a Drake toilet with routine tank part replacement will run 20 to 30 years without issue. Call (432) 547-6806 if you want us to walk the site and tell you exactly what you're working with.
Can a failing home addition be repaired instead of rebuilt? Yes, depending on what failed. Foundation issues can sometimes be corrected with piering. Plumbing rough-in errors can be fixed by opening the wall or slab at the affected fixture. But if framing is unsquare across multiple corners or the addition was built without permits, partial demolition and rebuild is almost always cheaper than chasing problems forever. Call (432) 547-6806 for an honest assessment, and we won't sell you work you don't need.
How long does a full home addition or ADU take in San Antonio? A garage conversion runs 8 to 12 weeks. A full addition runs 16 to 26 weeks. An ADU with its own kitchen and bath runs 20 to 32 weeks depending on site conditions and San Antonio permit review timelines. We'll give you a schedule with the written price, and we keep to it.
Do you stock Toto fixtures for additions and ADUs? We stock the Toto parts and fixtures most commonly needed for San Antonio builds: Drake and UltraMax toilets, Aquia wall-hung kits, matching lavatories, and the OEM repair parts that go with them. Most pieces are in our local inventory and on-site within days. If it's a specialty Toto finish, we order it direct and keep you posted on delivery. Call (432) 547-6806 and tell us what you're planning, and we'll tell you what's available and what the cost looks like.
For the fixtures and cabinetry around your Toto pieces, we also work with KraftMaid, Cambria, and Silestone, so the whole addition comes from brands you can actually name, not mystery supply whatever was on sale that week.
The craft comes first. Everything else follows.
Written by Luca Romano, Owner, Sawyer Remodel San Antonio at Sawyer Remodel San Antonio, serving San Antonio and nearby areas.
