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Kohler Home Additions & ADU: The San Antonio Owner’s Guide
Mason Remodeling Co San Antonio plans, permits, and builds home additions and ADUs that integrate cleanly with existing Kohler plumbing and fixtures, with installed projects in San Antonio typically running $45,000 to $130,000 for additions and $90,000 to $220,000 for detached ADUs. Most owners call us after realizing a bolt-on room or backyard unit is a bigger structural and plumbing job than a handyman can handle, often in older San Antonio homes where the existing Kohler drain lines or vent stacks don’t line up with any modern layout. Isaac Pruett has torn into enough San Antonio foundations to know that the difference between a clean addition and a nightmare is what’s underneath the slab, not just what shows on the drawings.
Which Kohler Models This Applies To
This page covers any home addition or ADU project where existing Kohler fixtures need to be tied into new plumbing runs, or where new Kohler fixtures get specified for the added square footage. Kohler’s lineup spans multiple rough-in standards, and the gotcha in San Antonio is older homes with 10-inch rough-in toilets or cast-iron drain stacks, which don’t play nice with Kohler’s newer 12-inch rough-in models like the Cimarron or Highline without some pipe rework. Our team checks the rough-in measurement, the drain slope, and the vent configuration before any walls come down, because a Kohler fixture that doesn’t match the existing waste system will either leak slowly or gurgle forever, and neither one is acceptable in a Texas crawlspace or slab.
When it comes to fixtures in the new space, we stock and install OEM Kohler parts and fixtures, along with aftermarket equivalents when the budget matters and the warranty trade-off makes sense. For an ADU with a compact bath, Kohler’s Reach or Persuade series fits smaller footprints while keeping the same water-pressure performance most owners expect. We also carry lines from KraftMaid, Cambria, and Silestone for cabinets and surfaces so the entire build comes from one crew instead of three different vendors fighting over the same schedule.
Styles & brands we work with
Signs Your Kohler Home Additions & ADU Is Failing
- Low water pressure in the new run, but fine everywhere else. Almost always a sizing issue on the PEX or copper branch we’re tying into, or an old galvanized stub hidden in the wall that nobody spotted during the walkthrough.
- Gurgling drains after a heavy rain. San Antonio’s clay soil shifts through the year, and an improperly supported new drain line will settle and lose slope within the first two seasons.
- Cracks at the seam where the addition meets the original structure. Different settlement rates between old slab and new slab, usually because the new footer wasn’t poured to account for San Antonio’s expansive soil.
- Humidity or mustiness in the added room. In our climate, a new room without proper vapor barrier or an undersized mini-split will turn into a terrarium by August, and the fix is rarely just a bigger fan.
- Noise from the water heater that wasn’t there before. Adding a second bath or a kitchenette to an existing tank means it now runs twice as hard, and a 40-gallon tank that was fine for two people becomes a lukewarm disappointment for four.
See the difference
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After
Before
After
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AfterReplacement Cost & What’s Included
In San Antonio, a tied-in home addition with a new bath or kitchenette runs $45,000 to $130,000 depending on square footage, foundation type, and how much of the existing Kohler plumbing we can leave in place. Detached ADUs start around $90,000 and climb toward $220,000 once you add a full kitchen, a second bath, and separate utility meters. The cost range covers architectural drawings, city permits, foundation work, framing, drywall, all plumbing and electrical rough-in, Kohler fixture installation, finish carpentry, paint, and a final walkthrough punch list.
Every quote includes a written line-item price before work starts, so there’s no “we discovered the slab was cracked” upcharge later. Isaac and his crew have spent enough years on San Antonio jobs to know where the surprises hide, and that’s reflected up front, not after the drywall is up. The 365-Day Done Right Promise applies to every addition and ADU we build: if something isn’t right within a year of completion, we come back and make it right at no charge. That’s not a handshake promise, it’s in writing with the coverage terms spelled out.
DIY or Call Us?
A homeowner can absolutely handle paint color, fixture selection, and even some demolition, but the moment you’re cutting into a load-bearing wall or tying a new drain into a cast-iron stack, DIY turns expensive fast. We’ve been called out to San Antonio jobs where a homeowner got halfway through a bathroom addition, hit a structural beam they didn’t expect, and then spent three weeks living with a tarp for a wall while they tried to find someone willing to take over a half-done project. Most contractors including us won’t touch someone else’s unfinished framing without tearing it back to the point where we can verify the work.
If you’re thinking about adding square footage in San Antonio, call (254) 269-5071 and we’ll walk the property, check the slab, the existing Kohler rough-ins, and the roofline, and give you a written price for the whole thing. That estimate is free, and it will tell you more in an hour than a month of online research.
FAQs
Most San Antonio additions run 10 to 16 weeks from permit approval to final walkthrough, and ADUs typically take 4 to 7 months depending on site prep, utility connections, and weather delays. The city’s permitting office has been moving slower on ADUs the last few years, so we submit early and stay on top of the review process weekly. Call (254) 269-5071 and we’ll give you a realistic schedule based on the scope, not a best-case number.
Yes, we regularly tie existing Kohler toilets, tubs, and sinks into new additions when the rough-in dimensions match the new layout, and that’s one of the ways we keep costs at the lower end of the range. The exception is when the fixture is decades old and the internal components are discontinued, at which point we tell you honestly what a replacement costs before you decide. Call us at (254) 269-5071 and we’ll assess what can stay and what needs to go.
No, the written price we deliver before your project begins is the price you pay unless you change the scope, and if we discover something unexpected, we stop work and bring it to you with a line-item cost before proceeding. Change orders only happen with your signature, never as a surprise invoice at the end. That’s the standard on every Mason Remodeling Co San Antonio job, and Isaac Pruett enforces it personally.
Yes, we pull every permit, schedule every inspection, and stay on the job until the final sign-off from the city of San Antonio is in hand, and that’s all included in the written price. We’ve done additions everywhere from the King William Historic District to quiet neighborhoods on the northeast side, and we know which inspectors want to see what, and in what order. Call (254) 269-5071 for a free estimate that includes the full permitting scope.
Written by Isaac Pruett, Owner, Mason Remodeling Co San Antonio at Mason Remodeling Co San Antonio, serving San Antonio and nearby areas.
Call (254) 269-5071 to schedule your free walkthrough and written estimate. Know who’s coming, know what it costs, know it’s covered – that’s the whole job before the job starts.
