A curbless shower in a Miami condo lives or dies on the half-inch under the floor. The owner wants a flat, gallery-clean entry from bath floor into shower. The building wants the bath-door sill untouched and the unit below kept dry. The job is to build a 1/4-inch-per-foot slope into a slab we cannot raise.

That is the install. Not the tile, not the glass, not the linear drain spec. The geometry of the pan against a fixed door sill on a high-rise is what decides whether the curbless shower works in a Brickell, Miami Beach, or Coral Gables condo. This is the spec we walk owners and designers through before any demo starts.

What is a curbless shower in a condo

A curbless shower — also called a zero-entry or zero-threshold shower — has no raised dam between the bath floor and the shower floor. The two planes meet flush, separated only by the slope built into the shower pan and a linear drain set at the wall. In a condo, the bath floor cannot rise, because the entry door sill, the toilet flange, and the vanity rough-ins are fixed. The slope has to be carved into the substrate, not added on top.

That single constraint — slope down, never up — is what separates a Miami condo curbless install from the same shower in a single-family slab home. In a house, we can pour 1.5 in of mud bed and feather it back to the bath floor. In a condo, we have 3/8 to 5/8 in of substrate to work with before we hit the structural slab or the post-tension cables.

Why curbless showers fail more often in Miami high-rises

Three failure modes account for almost every leak callback we see on a curbless install in a Miami condo.

The slope was built into the wrong plane. The installer poured a screed over the existing concrete and called it 1/4-inch-per-foot slope, then tiled the bath floor at the same elevation. Water pools at the threshold instead of moving to the drain. Within six months the entry grout joint darkens and the unit below logs humidity claims.

The waterproofing was lapped under the linear drain instead of bonded into it. A Schluter Kerdi-Line trough is engineered to receive the bonded membrane at a specific flange — not under the trough body, where any seepage runs along the slab toward the door.

The transition strip was forgotten. The bath-floor finish and the shower-floor finish often differ in thickness by 1 to 2 mm. Without a Schluter Schiene or a chamfered porcelain edge, the joint chips and water finds the underside.

These are the predictable result of treating the curbless shower like a curbed shower with the curb removed. The build sequence is different from the start.

How the slope gets carved without raising the bath floor

The work begins with a survey. We laser-scan the existing slab from the bath-door sill back to the shower wall and record the elevation at each foot. On a typical 30th-floor Brickell unit, the slab reads ± 4 to 8 mm of variation across an 8 ft run before any work. That variation is what we have to design around.

The target is a single-plane slope at 1/4 in per foot (2.08%) falling from the entry threshold to the linear drain trough. Across an 8 ft shower from bath sill to back wall, that is a 2 in (51 mm) total drop. We do not have 51 mm of substrate to give. The linear drain at the back wall has to sit at the lowest point — which means we carve the slab.

Substrate carve depth on a typical Miami condo curbless install:

Position from entry	Slab carve depth	Finished surface elevation
Entry threshold	0 mm	Bath floor plane
24 in into shower	-13 mm (1/2 in)	-13 mm
48 in into shower	-25 mm (1 in)	-25 mm
72 in into shower	-38 mm (1-1/2 in)	-38 mm
96 in (drain line)	-51 mm (2 in)	-51 mm

The carve is done with a wet-cut diamond grinder and a vacuum-shrouded surface planer. Depth is verified with a digital caliper at every grid line before any membrane goes down. This is also where the post-tension survey matters — if the original drawings show cables in the bath slab, we shift the drain trough to clear them and adjust the slope geometry around the constraint.

For floors where the slab variation is too inconsistent to grind cleanly, we use a thin-pour self-leveler against a perimeter dam to set a flat datum first, then re-mark the slope. The technique mirrors what we use on large-format porcelain hallway pours — see the Coral Gables hallway example documented in our Miami flooring material guide.

When the bath-door sill is fixed

On most Miami high-rises — Brickell, Edgewater, Sunny Isles, South-of-Fifth Miami Beach — the bath-door sill is part of the fire-rated unit-entry assembly and cannot be cut. Treat it as the immovable datum. Every elevation in the bath is measured down from that line.

If the existing bath floor is already at the sill (no transition gap), the linear drain has to absorb every millimeter of slope. We move the drain to the back wall, spec a Schluter Kerdi-Line at the longest run we can fit, and grind the slope toward it. If the existing bath floor is recessed below the sill — common in older Coral Gables condos — we pick up some headroom for the slope and the install gets easier.

Why the linear drain goes at the wall

A curbless shower with a center drain forces a 4-way slope, which means four separate planes meeting at four ridges. On large-format porcelain or stone, those ridges break the visual plane and force complex tile cuts. On a 1620 × 3240 mm Laminam panel, you cannot run a 4-way pitch — the panel will not bend.

A linear drain at the back wall (or a side wall) reduces the geometry to a single-plane pitch. The whole shower floor falls in one direction. Tile or slab cuts are straight. A 12 × 24 in porcelain plank, a 24 × 48 floor tile, or a 1620 × 3240 mm slab cut into floor strips can all sit on a single-plane pitch without diagonal cuts.

Schluter Kerdi-Line is the linear drain we spec on virtually every condo curbless install. The trough is available in lengths from 20 in to 72 in, takes a tileable cover for a flush look, and — critically — the integrated bonding flange accepts a Schluter Kerdi membrane bonded directly to the trough lip. No mechanical fasteners through the membrane. No silicone-lapped seam doing the waterproofing job. The full system is documented at Schluter Kerdi-Line and we walk the integration step by step on our linear drain installation service page.

For a 60 in linear drain at the back wall of an 8 ft shower, the trough invert sits 51 mm below the bath floor plane, the drain body sits another 38 mm below that to clear the trap arm, and the trap and connection to the existing 2 in shower drain stack happen below the slab — which on a condo means coordinating with the building engineer before the carve. This is condo-specific permitting, not optional. Our condo bathroom renovation rules in Miami covers the approval timeline most owners do not budget for.

The waterproofing layer — bonded, tested, then tiled

Once the slope is carved and verified, the pan gets waterproofed before any tile is set. We use Schluter Kerdi sheet membrane bonded with unmodified thinset to the carved substrate, lapped 2 in at every seam, and bonded to the Kerdi-Line drain flange with the manufacturer’s specified primer-and-bond detail. Corners get pre-formed Kerdi-Kereck inside-corner pieces. The wall-to-floor transition is a continuous wrap — the membrane runs up the wall a minimum of 6 in before it terminates behind the wall waterproofing.

The system meets ANSI A118.10 — the load-bearing, bonded waterproofing standard for tile assemblies. We hold the pan to the same A118.10 spec on a curbless install as we do on a curbed one. The curb is a comfort, not a code requirement; the membrane is the actual waterproofing.

After the membrane cures, the pan gets a 24-hour static flood test. We plug the drain, fill the pan to 1 in below the threshold, and walk away. If the water level drops more than 1/16 in over 24 hours, the membrane has not sealed. We tear it out and rebuild — the cost of a redo at this stage is two days of labor; the cost of a redo six months after tile is a full bath gut.

This is the same flood test we run on every Schluter install, condo or single-family — detailed in our pillar guide on shower waterproofing in Miami and the comparison of bonded vs sheet systems in Schluter Kerdi vs sheet membranes. The flood test is the only honest answer to “is the shower waterproof yet.”

ADA and accessibility — when curbless meets a fixed door sill

A true ADA-compliant zero-threshold shower per ICC A117.1 §608 requires no more than a 1/2 in vertical change at the entry, beveled at 1:2 maximum. That is achievable in most Miami condos, but only if the bath-door sill happens to sit no more than 13 mm above the carved shower-pan plane. In practice, on a high-rise where the door sill is fixed and the slab carve is constrained, we hit “curbless visual” and “near-ADA threshold” — we usually cannot certify full A117.1 §608 without coordinating with the building on a sill modification.

For owners who require true wheelchair-accessible compliance, we flag this in the survey before demo. The conversation usually moves toward either a different unit, a re-routed entry, or a ramped transition outside the bath. We do not promise ADA compliance we cannot deliver inside the existing condo envelope.

When The Miami Floors is the right fit

Curbless showers in Miami condos are a coordination problem before they are an installation problem. The slab carve, the post-tension survey, the building plumbing tie-in, the HOA waterproofing addendum, the 24-hour flood test with the building manager present — all of it has to happen in sequence, before tile.

The Miami Floors is Schluter certified. We work in Brickell, Miami Beach, Coral Gables, Key Biscayne, and Pinecrest. Ivan Herrera personally walks every curbless project at survey, at the post-carve elevation check, and at the 24-hour flood-test pass. The crew handles Laminam, Neolith, and Dekton large-format porcelain on the pan and walls — see large-format porcelain installation in Miami for the slab side of the install — and integrates Schluter Kerdi waterproofing, custom shower systems, and Kerdi-Line linear drains under one license.

If you are planning a curbless or zero-threshold shower in a Miami condo, the survey is the first step. We come out, laser the slab, pull the unit drawings if the building has them, and tell you in writing whether the slope can be built into the substrate you have — before any demo. The bath-remodel side of the conversation is covered in our bathroom remodeling Miami guide, and the Brickell-specific HOA realities are in bathroom renovation in a Brickell condo.

Reviewed by Ivan Herrera, Founder, The Miami Floors — Schluter certified, April 2026.

Curbless Shower in a Miami Condo: How the Slope Is Built