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Schluter Home Additions & ADU: The Miami Owner’s Guide
Schluter-compatible home additions and ADU construction in Miami typically run $53,100 to $153,400 installed, and we price every job in writing before the first tool shows up. Most owners call us because their existing space has stopped working: a garage conversion that never got properly waterproofed, an ADU shell that’s leaking at the floor-to-wall transitions, or a bump-out where the tile membrane failed and the subfloor is now swelling with humidity. We stock Schluter systems – KERDI-BOARD, KERDI membrane, DITRA, and the edge trims – on our trucks, so when we open a wall during a Miami ADU build and find a failed transition, we fix it that week, not after a two-week parts order.
The honest version: Miami’s humidity and rainfall expose every weak point in a home addition faster than almost any climate in the country. A Schluter system installed correctly handles that. Installed wrong – or paired with the wrong substrate – it fails within one to two wet seasons, and by the time you see the damage, the repair is no longer just about the membrane. That’s where we come in.
Which Schluter Models This Applies To
In home additions and ADU work, the Schluter products we install and replace most often fall into three families: KERDI (the orange waterproofing membrane and KERDI-BOARD panels that wrap showers, tub surrounds, and wet walls), DITRA and DITRA-HEAT (the uncoupling membranes that go under tile floors, including heated floors in ADU bathrooms and kitchens), and the metal edge trims – SCHIENE, RONDEC, QUADEC – that finish tile edges at floor transitions and doorways. Each has a specific compatibility range, and guessing wrong is the most expensive mistake in this trade.
The compatibility gotcha most people miss: KERDI membrane only bonds to a *fleece-backed* substrate – drywall, cement board, or KERDI-BOARD. Slap it over plywood or OSB with unmodified thinset and it will peel like a bad sticker. We see that exact failure at least twice a month in Miami, usually in garage conversions where a previous contractor cut a corner. Schluter DITRA requires the square notches in the felt to face down into the thinset; install it upside down and you get hollow-sounding tile that cracks within a year. In Florida’s clay-heavy soil, slab movement makes the uncoupling layer non-negotiable – skip it and the tile will telegraph every ground shift as a crack.
We recommend OEM Schluter membrane and board every time. Aftermarket off-brand membranes exist, but there’s no meaningful price savings once you factor in the warranty and the cost of tearing out a failed floor. For edge trims, quality aftermarket equivalents work fine visually – but Schluter’s aluminum and stainless trims are thicker-walled, so they resist denting when a wheeled cart runs into a tile edge in a Miami ADU kitchen.
Styles & brands we work with
Signs Your Schluter Home Additions & ADU Is Failing
- Grout lines darkening or mold appearing at the base of a shower wall. This means moisture is sitting behind the tile, not draining through the KERDI system. The membrane was likely installed without the required 2-inch overlap at the seams, or the sealant backer rod at the floor transition was skipped.
- Tile that sounds hollow when tapped with a screwdriver handle. The thinset has debonded from the membrane or the substrate below. In a Miami ADU built over a garage slab, this is almost always a DITRA install with notched-side-up mistakes or thinset that cured too fast in high heat.
- Water staining on the ceiling of the room below a second-story addition bathroom. The pan wasn’t flood-tested before tile went in, or the drain flange was never sealed to the membrane. By the time you see the stain, the subfloor and possibly a joist are already compromised.
- Persistent musty smell in the addition even after cleaning. Moisture has been trapped behind the tile or inside a wet wall for months. In Florida’s climate, that turns into a mold problem far before the tile itself shows visible damage – and it’s worse in windowless ADU bathrooms without proper exhaust.
- Cracked tiles running in a straight line from a doorway in a slab-on-grade addition. The slab has a control joint and there’s no movement joint in the tile layer above it. Schluter makes dedicated movement joint strips – DILEX – and bypassing them means the crack will always come back, no matter how many times you replace the tile.
See the difference
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AfterReplacement Cost & What’s Included
Here’s what Schluter-related home addition and ADU work actually costs in Miami. These are all-in ranges – materials, labor, and the Schluter components – and the final number depends on what’s already failing behind the surfaces.
| Project | Installed Price Range (Miami) |
|---|---|
| Home Addition | $53,100 – $153,400 |
| ADU Construction | $106,200 – $259,600 |
| Garage Conversion | $35,400 – $94,400 |
| Bathroom Remodel | $10,620 – $33,040 |
| Small Bathroom Remodel | $5,900 – $14,160 |
| Walk-In Shower Installation | $5,310 – $14,160 |
| Kitchen Remodel | $16,520 – $53,100 |
Every quote we write in Miami includes the Schluter product by name and spec, the square footage being covered, the labor to demo and rebuild if a failed membrane means taking tile off, and a written line-item breakdown before any work begins. Our 365-Day Done Right Promise covers the workmanship and the materials for a full year – if something fails because we installed it wrong, we make it right, in writing, on every project. No change orders at the door but quote low. The price you approve is the price on the invoice.
DIY or Call Us?
There’s exactly one thing worth your time as a homeowner: the visual inspection. If you’re seeing grout discoloration, hollow tile, or water stains, you’ve confirmed you have a problem – but you haven’t found the extent of it, and that’s where DIY ends for this work. Water travels. A failed Schluter membrane in a Miami shower often means water has been traveling sideways inside the wall or under the floor for months before the first surface symptom shows. Opening that up without the right materials and the right eye turns a $1,100 patch into a full re-waterproof and retile, and at worst, you’re into subfloor and joist repair before you know it.
The one thing you can do safely: stop using the affected area until it’s looked at. Slab moisture, mold, and compromised framing get worse every week in Florida AC cycles. After that, call us at (850) 801-8046. Luca Romano’s crew has opened enough failed additions and ADUs across Miami to tell you in the first five minutes whether you’re looking at a repair or a full replacement, and the estimate is free either way. Good work doesn’t need a sales pitch – it needs the right membrane, the right overlap, and someone who knows what DITRA looks like installed upside down.
FAQs
Installed correctly, Schluter KERDI and DITRA membranes have a realistic lifespan of 30+ years in Miami’s climate – the limiting factor is always the installation, not the material. Failed installs typically show symptoms within one to two wet seasons, which is why a 2007 garage conversion with a properly lapped membrane often still looks new while a 2021 flip shower is already growing mold at the base. Schluter’s published warranty on KERDI covers 10 years when installed using Schluter thinsets, but failures after year two in Florida are almost always an install error, not a product defect. Call (850) 801-8046 if you want someone to determine which one you’re dealing with.
In most cases, no – not in a way that holds. A seam leak can sometimes be patched if it’s caught before water reaches the substrate, but by the time you see staining or smell mold in a Miami addition, the water has traveled beyond the seam, and the only honest fix is opening the tile, replacing the affected membrane section with proper 2-inch overlaps, and rebuilding the area. We’ll always quote the least invasive effective fix first, but patch jobs on wet walls are a bill-doubling mentality, not a real repair.
A shower membrane replacement – demo, waterproofing, 24-hour flood test, retile, and grout – runs four to six working days. A floor membrane like DITRA under a failed tile floor in a Miami home addition runs three to five days, depending on whether the concrete below needs leveling. The flood test comes before any tile goes on, and anyone who skips it isn’t doing Schluter work – they’re doing guesswork.
We stock KERDI membrane in common widths, KERDI-BOARD in half-inch and two-inch, DITRA and DITRA-HEAT mats, KERDI-BAND, inside and outside corners, pipe seals, mixing valve seals, and the standard SCHIENE/RONDEC edge trims on our trucks. Special-order items – a specific trim profile in a non-stock finish, or a DITRA-HEAT cable length outside the common range – typically land at our Miami shop in two to three business days. Call (850) 801-8046 and we’ll tell you same-day whether what you need is on the truck or on order, and quote you a price either way.
Written by Luca Romano, Owner & Lead Contractor, Sawyer Remodel Miami at Sawyer Remodel Miami, serving Miami and nearby areas.
