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Schluter Home Additions & ADU: The Orange County Owner’s Guide
A Schluter-specified home addition or ADU in Orange County typically runs $45,000 – $130,000 when we handle the full scope, from waterproofing substrate to finished surfaces. That’s the honest range for a permitted addition, and it’s the number you should anchor to before anyone starts tearing into your existing roofline.
Most homeowners don’t discover a problem with their Schluter system until water stains show up on the ceiling below a second-story addition, or the tile in a newly built ADU shower starts sounding hollow. The Schluter components themselves rarely fail on their own. What fails is what’s behind them: a seam that wasn’t properly bonded, a drain collar that shifted during backfill, or a substrate that moved more than the membrane could tolerate. By the time you see it, the part that failed is usually buried under tile and thinset.
Which Schluter Models This Applies To
Schluter doesn’t make “home additions” as a product line. What they make is the waterproofing and uncoupling system that holds an addition together: KERDI-BOARD for wall substrates, KERDI membrane for shower and wet-area waterproofing, DITRA and DITRA-HEAT for floor uncoupling, and KERDI-LINE and KERDI-DRAIN for linear and point drainage. If your addition or ADU project specified Schluter, the part that’s failing is almost always one of these, and model compatibility matters.
The gotcha most Orange County homeowners hit: KERDI membrane from a big-box store is not the same thickness as the commercial-spec KERDI-DS we order through our supply chain. KERDI-DS runs thicker (around 0.5 mm) and is rated for continuous water exposure, which matters in a wet room or an ADU bathroom that gets daily use with no ventilation upgrade. If a previous contractor used standard KERDI where KERDI-DS was specified, the failure shows up within 3 to 5 years, not 20. We check the lot stamp on the membrane edge to confirm what’s actually in your wall before we quote a repair.
Styles & brands we work with
Signs Your Schluter Home Additions & ADU Is Failing
- Water staining on the ceiling below an addition. The most common first sign in two-story Orange County homes. Usually means a KERDI seam or pipe penetration wasn’t bonded correctly, and water is traveling along the framing. By the time you see the stain, the membrane has been leaking for weeks.
- Hollow-sounding tile in a new ADU shower or bathroom floor. This means the tile has debonded from the DITRA or KERDI beneath it. In Orange County’s dry inland heat (think Anaheim Hills or Yorba Linda summers), rapid curing of thinset during installation can cause this if the installer didn’t work fast enough or back-butter the tile.
- Musty smell in a wall cavity after rain. Schluter systems handle interior moisture well, but if the exterior weather barrier wasn’t lapped correctly over the Schluter edge at a junction, wind-driven rain from a coastal storm in Huntington Beach or Newport gets in. The smell comes before the stain.
- Cracked grout lines radiating from a corner in the addition. Uncoupling membranes like DITRA exist to absorb subfloor movement. If the membrane wasn’t carried corner-to-corner with the proper expansion joint, the tile itself takes the stress. Orange County’s expansive clay soils in inland areas make this worse than people expect.
- Standing water at the drain in a Schluter KERDI-LINE shower. The KERDI-LINE collar has to be set dead level at rough-in. If it’s off by even 1/8 inch over 4 feet, water pools and the grout never dries. You’ll see darkened grout lines first, then efflorescence.
See the difference
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After
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Before
AfterReplacement Cost & What’s Included
Here’s what we quote in Orange County, written line by line so you know exactly what you’re paying for:
- Full home addition (permitted, from foundation to finish): $45,000 – $130,000. The spread depends on whether you’re adding a single room or a full primary suite with wet areas, the condition of your existing framing, and how much trenching your foundation work requires.
- ADU construction (detached or garage conversion): $90,000 – $220,000. Detached ADUs in cities like Irvine and Fullerton often trigger additional setback and fire-rating requirements that a conversion won’t.
- Garage conversion to ADU: $30,000 – $80,000. The lower end assumes your garage slab and roof are sound and we’re not rebuilding either.
- Schluter-specific repair work inside an existing addition or ADU (e.g., failed shower waterproofing, failed DITRA floor): $3,000 – $10,000 depending on how much tile and substrate has to come out.
Every quote includes the written price before we start, the named Schluter materials we’ll use, and the 365-Day Done Right Promise in writing. If the repair doesn’t hold within a full year, we come back and correct it at no charge. No exceptions, no arguing about whose fault it was.
DIY or Call Us?
You can check the obvious stuff yourself: look for visible seam gaps at any exposed KERDI edge, check whether the drain collar sits level, and note exactly when the stain or odor appears (after rain, after showers, or constant). That information saves us a full diagnostic hour when we arrive.
What you should not do is start peeling back tile to “see what’s under there.” Schluter’s waterproofing only works as a continuous plane. Once you pierce it, you’ve changed the scope from a targeted repair to a full flood-plane rebuild, and you’ve turned a $3,000 fix into a $10,000 one. Water damage under tile is also where mold gets a foothold, and that’s a health issue, not a tile issue. Call (562) 262-2907 and we’ll get a crew lead out to look at it properly.
FAQs
When installed to spec with the correct membrane grade and proper bonding, a Schluter system should last the life of the structure, which realistically means 25 to 40 years before any material degradation. The failures we see in Orange County are installation failures, not product failures, and almost all of them show up within the first 5 years. If your Schluter system failed early, the install was wrong, not the material. Call (562) 262-2907 and we’ll confirm what happened and quote the proper fix.
Sometimes, if the failure is localized to one seam or corner and the surrounding membrane is still soundly bonded. We can open the affected area, patch with fresh KERDI at the proper overlap, and retile. But if water has wicked along the seam more than a foot or two, the membrane has to come out to a dry, sound substrate. We’ll tell you which situation you have before we quote, not after. Call (562) 262-2907 for a free estimate.
Most single-seam or single-wall repairs run 2 to 4 working days including tile replacement. A full wet-area rebuild (shower floor, walls, and drain) typically runs 5 to 7 days. We work on a set schedule and give you the day count in writing before we start. Call (562) 262-2907 and we’ll give you a straight number on both the timeline and the cost.
We stock KERDI membrane, KERDI-BAND, KERDI-KERECK preformed corners, DITRA, and KERDI-LINE drain collars in our Orange County shop, and we carry standard sizes on every service truck. Specialty items like KERDI-DS or custom linear drain lengths are ordered and on-site within 2 to 3 business days. We’re an independent contractor, not a Schluter-affiliated dealer, so we also work across other brand systems: KraftMaid, Cambria, and Silestone among the names we install and service.
Written by Curtis Lane, Owner, Bradford Remodeling Co – Orange County at Bradford Remodeling Co Orange County, serving Orange County and nearby areas.
Straight number, clear scope, no surprises at final invoice. Call (562) 262-2907 to schedule your free estimate.
