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Schluter Home Additions & ADU: The Miami Owner’s Guide
Schluter home additions and ADU construction in Miami typically run $53,100 to $153,400 installed, depending on square footage, foundation work, and whether you’re building up or out. We stock Schluter-compatible waterproofing, uncoupling membranes, and edge profiles for additions and ADUs, and we can usually start the structural phase within two weeks of permit approval. Most owners call us after water intrusion at the sill plate or tile cracking along the seam where the new slab meets the existing foundation.
Here’s the reality in Miami: our humidity, salt air, and seasonal downpours put Schluter materials through more stress than they’d ever see in a dry climate. A poorly flashed addition leaks within the first rainy season. A properly detailed one built on Schluter’s KERDI and DITRA systems lasts decades without a callback. That’s the difference between paying once and paying twice. Isaac Pruett has torn out enough failed additions in Coconut Grove to know which one you’re looking at.
Which Schluter Models This Applies To
If your addition or ADU uses Schluter waterproofing or uncoupling systems, the relevant product lines are KERDI-BOARD (wall substrate), KERDI membrane (shower and wet-area waterproofing), DITRA and DITRA-HEAT (uncoupling underlayment for tile over concrete or wood subfloors), and Schluter edge profiles (finishing strips at transitions and thresholds). The part that fails most often in Miami additions isn’t the membrane itself. It’s the seam where Schluter meets a non-Schluter penetration: a plumbing stub-out, a window buck, or the joint between new framing and existing block wall.
OEM Schluter parts are specific to their system, and using an aftermarket membrane or off-brand edge profile voids the Schluter warranty outright. We’ve seen it happen: a homeowner saves $40 on a generic corner, the seam opens, water gets behind the tile, and now the entire shower curb in a $100,000 ADU has to come out. We stock OEM KERDI band, KERDI-KERECK preformed corners, DITRA mat, and a range of Schluter edge profiles on our trucks. For most Miami additions, that covers 90% of warranty-backed repairs without a parts order.
One compatibility gotcha: Schluter edge profiles come in specific heights matched to tile thickness. A Jolly 3/8-inch profile won’t finish a 1/2-inch porcelain tile edge cleanly. Measure your tile thickness before ordering, or call us and we’ll match it from stock.
Styles & brands we work with
Signs Your Schluter Home Addition or ADU Is Failing
- Efflorescence or white chalk on the block wall at the addition seam. Water is wicking through the joint where new slab meets existing foundation. That joint needed a Schluter expansion profile, and it either wasn’t installed or has failed.
- Musty odor inside the ADU within the first year. Moisture is trapped behind the wall substrate. In Miami’s humidity, that converts to mold fast. This almost always traces to a missed KERDI seam or an unbanded penetration.
- Cracking tile at the threshold or along the exterior wall. Differential movement between the old structure and the new addition is shearing the tile. DITRA mat allows lateral movement; missing DITRA means the tile takes the stress directly.
- Soft or buckling laminate or wood flooring near the addition’s exterior door. Flashing at the door pan failed, or the Schluter transition was never sealed at the jambs. Miami’s wind-driven rain finds every gap.
- Visible rust staining on Schluter edge profiles. In coastal Miami air, aluminum profiles hold up, but cheap brass or uncoated steel aftermarket profiles corrode within two to three years. If the profile is rusting, moisture is pooling at the transition.
See the difference
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AfterReplacement Cost & What’s Included
For Miami additions and ADUs using Schluter systems, here’s what the work costs. A full ADU with one bath and a kitchenette typically runs $106,200 to $259,600. A garage conversion with Schluter waterproofing at the bath and laundry runs $35,400 to $94,400. A single-room addition with full Schluter water management at the envelope runs $53,100 to $153,400.
- Structural and envelope work on a single-room addition: $53,100 – $153,400
- Full ADU with Schluter wet areas (bath, kitchenette): $106,200 – $259,600
- Garage conversion including Schluter waterproofing: $35,400 – $94,400
- Schluter membrane repair at a failed seam or corner: $710 – $2,950
What drives the range: slab-on-grade versus elevated (Coral Gables and parts of Coconut Grove have fill issues that mean deeper footers), whether the existing roofline ties in cleanly or needs reframing, and whether we’re repairing a failed Schluter detail or installing new. Every quote is a written, line-item price before we touch the job. No change orders, no verbal estimate that grows. Our work carries the 365-Day Done Right Promise: if anything isn’t right within one year of completion, we make it right at no cost.
DIY or Call Us?
You can check the obvious: look for visible cracking at the slab seam, run a hose against the exterior wall for ten minutes and check for dampness inside, and inspect edge profiles for gaps or corrosion. What you should not do is tear into a Schluter membrane seam yourself. Once the waterproofing layer is compromised, a partial repair creates a false sense of security; the seam has to be stripped, cleaned, re-banded with overlapping KERDI, and flood-tested before tile goes back. That’s not a weekend job. It’s also not a handyman job. A failed flood test after tile is set means the whole wall comes out again.
If you’re seeing any of the failure signs above, call (850) 780-8123. We’ll send a background-checked, uniformed technician with a photo ID badge; you’ll have their name and photo before the visit. We give you a written diagnosis and a written price.
FAQs
OEM Schluter KERDI and DITRA systems, installed correctly and with proper flashings at all penetrations, last 30-plus years in Miami’s climate. The failure point is rarely the membrane. It’s the seam detailing or the use of off-brand components that void the warranty. Installed right, the system outlasts the tile on top of it. Call (850) 780-8123 if you suspect a seam issue and we’ll assess it.
It can almost always be repaired if the leak is caught early. We strip the tile at the failed seam, expose the membrane, clean the surface, re-band with KERDI and KERDI-KERECK corners, and flood-test before retiling. If water has been sitting behind the wall long enough to rot framing, that framing section gets replaced. The cost difference between early repair and full tear-out is thousands of dollars in Miami. Get a free estimate before the damage spreads.
A failed seam repair takes two to three days including flood test, cure time, and retile. A complete ADU waterproofing package on new construction adds roughly one to two weeks to the build, depending on square footage and number of wet areas. We give you a written schedule with the quote, and we mean it.
We stock OEM KERDI band, KERDI-KERECK corners, DITRA mat, and common Schluter edge profiles on our trucks in Miami. Specialty profiles or unusual sizes may need a parts order, which typically takes three to five business days. We also stock compatible parts from KraftMaid, Cambria, and Silestone for finish work that ties into your addition. Call (850) 780-8123 and we’ll tell you same day whether it’s on the truck.
Tell me what you need done. I’ll tell you what it costs and when it’s finished – and I’ll mean both.
Call (850) 780-8123 to schedule your free estimate. A live person answers, every call, 24 hours a day, 7 days a week.
Written by Isaac Pruett, Owner, Mason Remodeling Co Miami at Mason Remodeling Co Miami, serving Miami and nearby areas.
