Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
Toto Home Additions & ADU: The San Antonio Owner’s Guide
We install and build Toto-compatible home additions and ADUs in San Antonio, with complete projects typically running $45,000 to $130,000 depending on square footage, foundation work, and finish level. Most homeowners call us for the first time after a Toto product they own, usually a toilet or washlet, has failed in a guest bath or ADU they are planning to expand, and they want a contractor who already knows the Toto rough-in dimensions and valve compatibility before framing begins. The written price you sign is the price you pay, and we walk every San Antonio project with you before a single permit is pulled.
Graham Stein, who leads our San Antonio crew, grew up in Los Angeles and learned construction at Los Angeles Trade-Technical College before spending decades framing and finishing homes. He has worked on additions near the King William Historic District where older foundations and original plumbing demand patience. His rule on every Toto-involved addition: write down the exact fixture list, price it once, and do not add line items after demo day.
Key Takeaways
- Toto-compatible additions and ADUs in San Antonio run $45,000 – $130,000 complete, with a written price before work starts.
- We match Toto rough-in specs (10-inch, 12-inch, and 14-inch) and washlet electrical requirements before walls are closed.
- We are an independent contractor, not affiliated with Toto, but we install and build around their products every month.
- Every project carries the 365-Day Done Right Promise: if it is not done right, we make it right.
Which Toto Models This Applies To
When San Antonio homeowners plan a home addition or ADU around existing Toto fixtures, the compatibility question comes down to model series and rough-in dimensions. Toto toilets generally ship with 12-inch rough-ins, but the Carlyle II, Legato, and select Neorest models can require 10-inch or 14-inch rough-ins depending on the year and the carrier system. A washlet, like the Toto S7A or C5, needs a dedicated GFCI outlet within a specific distance of the bowl, and if the ADU is on a slab in a place like Stone Oak or Alamo Ranch, that outlet placement has to be decided before the concrete pour, not after. We flag this in the written scope so the electrician and the plumber are not discovering it on trim day.
The OEM-versus-aftermarket decision for Toto parts comes up most often with washlet hoses, fill valves, and flush tower gaskets. For a home addition, we recommend OEM Toto fill valves and flush mechanisms because the tolerances on the flush tower and the bowl gasket are tight enough that a generic part can cause a slow ghost-flush, which wastes water and drives up the SAWS bill. For washlet supply lines, a quality braided stainless line from a brand like Fluidmaster works fine and is what we keep on the truck. The one place we do not compromise is the Toto bowl-to-tank coupling gasket, because aftermarket versions compress wrong and leak slowly behind a new wall where you will not see it until the baseboard swells.
Styles & brands we work with
Signs Your Toto Home Additions & ADU Is Failing
- Rocking or shifting fixture during planning. If a Toto toilet in the existing part of the house rocks on the flange, the flange is either cracked or the subfloor is soft. We fix that structural issue before tying the new addition into the same waste line, otherwise the new work inherits the old problem.
- Flush sound changes from a clean siphon to a gurgle. A Toto G-Max or Tornado Flush should evacuate quickly. A gurgle or double-flush usually means a partially blocked vent stack or a failing flush tower seal, and in a San Antonio attic, a cracked vent pipe from temperature swings is more common than homeowners expect.
- Water staining at the base of a Toto bowl after a hard Hill Country freeze-thaw cycle. The wax ring or the Toto Uni-Fit adapter has lost its seal. If the addition will tie into the same slab, we inspect this before framing so the new flooring does not go down over a slow leak.
- Washlet throws an error code or stops heating. This is often the inlet filter screen clogging with San Antonio’s hard water sediment, or a failing power supply, not the washlet itself. We check the filter and the GFCI load before recommending any replacement part.
- Toilet in the ADU takes multiple flushes or the bowl water level drops. A dropping bowl level points to a hairline crack in the Toto trapway or a failing flapperless seal. When it happens in a new ADU, it is almost always a rough-in or venting issue, not the fixture.
See the difference
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After
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After
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AfterReplacement Cost & What’s Included
A full Toto-compatible home addition in San Antonio runs $45,000 to $130,000. An ADU built from the ground up generally lands between $90,000 and $220,000 depending on foundation type, utility runs, and finish level. A garage conversion with a Toto bath added starts around $30,000 and can reach $80,000 when the scope includes a full kitchenette and separate HVAC. The biggest cost drivers in our area are foundation work, which shifts depending on whether you are on clay soil near Leon Valley or limestone near the Dominion, and the utility extension distance from the main house to the ADU.
Every quote from us includes the written scope, the named materials, the permit fees, the dumpster, and the labor. We use Toto OEM parts for flush mechanisms and trapways, and we specify where Kohler or Moen fixtures are used for the shower and lavatory. Drop cloths on the floors, shoe covers at the door, and a photo of the clean-up before the crew leaves are included on every job, not charged as add-ons. The work carries a 365-Day Done Right Promise. If something is not right after we finish, we come back and make it right.
San Antonio Project Cost Ranges
- Home Addition – $45,000 – $130,000
- ADU Construction – $90,000 – $220,000
- Garage Conversion – $30,000 – $80,000
- Bathroom Addition (within a larger project) – $9,000 – $28,000
- Small Bathroom Remodel – $5,000 – $12,000
DIY or Call Us?
There are a few Toto checks a San Antonio homeowner can do safely before calling anyone. Look at the water shutoff valve behind the toilet and confirm it opens and closes fully, because if an ADU is going in, that valve may need to move. Check the GFCI outlet serving an existing washlet, since the new addition will likely share or extend that circuit. Read the model number off the inside of the Toto tank, because we need it to confirm rough-in and parts compatibility. Those are all safe, useful steps.
What an owner should not do is relocate the waste line, cut into a post-tension slab, or run a new circuit for a washlet without a licensed electrician and a permit. San Antonio has specific amendments to the plumbing and electrical codes, and a Toto washlet on a shared circuit trips more often than people expect. If the Toto part itself is leaking or the fixture needs reseating, call us at (432) 233-0976. We will tell you over the phone whether it is a fifteen-minute part swap or a rough-in correction, and the estimate is free.
FAQs
A Toto toilet with OEM parts typically lasts 20 to 30 years in San Antonio, though hard water and the freeze-thaw cycles in older homes near Monte Vista can shorten the lifespan of seals and fill valves to 8 to 12 years. A washlet power supply usually lasts 7 to 10 years. If you are planning an addition that ties into existing Toto plumbing, call (432) 233-0976 and we will tell you what still has life in it and what should be replaced before the walls close.
Yes, in most cases the flush tower gasket, fill valve, or the inlet filter screen can be replaced with OEM Toto parts in under an hour. We only recommend full replacement when the bowl or trapway is cracked, or when a washlet control board fails on a unit over ten years old. Call (432) 233-0976 for an exact assessment, and we will give you a written repair price before any work starts.
A typical home addition takes 10 to 16 weeks depending on foundation and finish work, and an ADU usually runs 5 to 8 months from permit to final inspection. San Antonio permitting and inspections add time, and we schedule the quiet-tool work around nap and school hours where possible. The timeline is written into your scope before we start, and we do not add change orders after demo day.
We keep common Toto OEM fill valves, flush tower gaskets, washlet inlet filters, and braided supply lines on the truck, so a standard repair is often done the same visit. Specialty parts for Neorest or older Carlyle models may need a supply house order, and we will tell you the exact lead time before you pay anything. Call (432) 233-0976 and a live person will answer, any hour of the day.
No. We give a written price before any work starts, and the price you sign is the price you pay. If we find an unexpected condition during framing or foundation work, we stop, explain it, and give you a written change order to approve before proceeding. We do not add line items after the fact. Graham’s rule on every project is the same: write it down, price it once, do it right.
We are an independent San Antonio contractor, not affiliated with Toto. We also work with parts and materials from KraftMaid, Cambria, and Silestone on the finish side. If your Toto fixture is part of an addition or ADU you are planning, or you have a Toto part failing right now, call (432) 233-0976 for a free estimate. A live person answers, we will ask the right questions, and we will send someone who knows exactly which Toto spec your project needs.
Written by Graham Stein, Owner, Elmstead Remodeling San Antonio at Elmstead Remodeling San Antonio, serving San Antonio and nearby areas.
