5 Signs Your Shower Tile Was Installed WrongAnd What to Do About Each One

Updated April 2025 · 10 min read · By the Tilers4you team, Aurora CO

Tile work hides its mistakes for a while. A shower might look perfect the day it's finished and start showing problems six months or two years later. By then, you've paid the contractor, they've moved on, and you're left figuring out what went wrong and how to fix it.

This guide walks through the five most common signs of bad tile installation — what they look like, what caused them technically, and whether you're looking at a simple repair or a full tear-out.

A quick test: Knock on your tile with your knuckles. A solid tile sounds like tapping on concrete — a thud. A tile with voids beneath it sounds hollow — higher-pitched, almost like tapping on a door. If you hear hollow spots, especially on multiple tiles, you have a problem.

Sign #1: Grout Cracking at Corners

Severity: Moderate — fixable without demo

What You'll See

Grout that cracks or separates along inside corners — where the floor meets the wall, or where two walls meet. The crack might run the full height of the wall or appear as a series of gaps. You might also notice the corner looking slightly darker as moisture gets into the cracked joint.

What Went Wrong Technically

Inside corners must be filled with caulk — not grout. This is explicitly required by the TCNA Handbook as part of the movement joint requirements. Here's why it matters:

Buildings move. Temperature changes cause materials to expand and contract slightly. The tile, the mortar, the backer board, and the framing all move at slightly different rates. At inside corners — where two perpendicular surfaces meet — this movement is concentrated. A rigid material like grout can't flex to accommodate that movement, so it cracks. Caulk is flexible by design and handles this movement indefinitely without failing.

An installer who grouted all corners either didn't know this requirement or skipped it to save time.

Can It Be Fixed?

Yes — without full demo. Remove the cracked grout from all inside corners using an oscillating tool or grout saw. Clean the corner thoroughly. Apply 100% silicone caulk (or a sanded caulk that matches your grout color, if available) in a color matching the existing grout. Smooth with a wet finger. This is a legitimate permanent repair as long as the tile itself is still bonded and the waterproofing below wasn't compromised.

Sign #2: Hollow or Loose Tiles

Severity: High — usually requires tile replacement

What You'll See

Tiles that move when pressed, or that make a hollow sound when tapped. In severe cases, grout lines crack around the hollow tiles as the unfixed tiles shift under use. Eventually, hollow tiles break, pop off the wall, or crack diagonally.

What Went Wrong Technically

This is a thinset coverage failure. ANSI A108.01-3.8 requires minimum 80% mortar contact coverage for floors in dry areas and a minimum 95% coverage for floors in wet areas (like shower floors) and for wall tile in wet areas.

"Coverage" means the percentage of the tile's back surface that is actually bonded to mortar. When a contractor uses a trowel that's too small for the tile size, skips back-buttering, or rushes the setting process, large voids form between the tile and the substrate. The tile bonds only at the ridges of the combed thinset pattern, leaving the valleys as empty air pockets.

In a shower, these air pockets trap water, accelerate damage, and — in the case of wall tiles — gravity eventually wins and the tile falls off.

Can It Be Fixed?

Hollow tiles need to be removed and re-set. If the hollow tiles are isolated (one or two), a careful repair is possible without disturbing the whole installation. However, if hollow tiles are widespread, the installer likely skipped back-buttering and used the wrong trowel consistently — which means most of the tile has inadequate coverage, even the tiles that happen not to be hollow yet. In that case, a full re-do is the honest answer.

Sign #3: Visible Lippage — Tile Edges That Stick Up

Severity: Moderate to High — depends on extent

What You'll See

When you run your bare foot across the floor, you feel a bump at tile edges — like a miniature curb. Under raking light (light hitting the tile at a low angle), you can see shadows along the edges of misaligned tiles. This is called "lippage."

What Went Wrong Technically

Lippage happens when adjacent tiles aren't set at the same height. The root causes:

• Substrate not flat enough. If the floor has high and low spots exceeding the tolerance (⅛ inch over 10 feet), tiles bridging those spots will naturally have mismatched edges. No amount of skill can overcome an inadequately prepped substrate.
• Inconsistent mortar bed thickness. If the installer didn't use consistent trowel pressure and technique, the mortar bed will be thicker in some spots and thinner in others, causing height variations.
• No leveling system used. For large format tile especially, tile leveling clips and wedges are how professionals prevent lippage. Skipping this tool on a large-format job almost guarantees some lippage.
• Inherent tile warpage. Porcelain tiles fired at high temperatures often have a slight bow or warp. An experienced installer accounts for this during layout; an inexperienced one ignores it.

Can It Be Fixed?

Minor lippage (less than 1/16 inch in isolated spots) can sometimes be ground down with a hand grinder and diamond pad — a skilled mason can feather out slight height differences. Significant or widespread lippage generally means re-doing the floor, including proper substrate preparation this time.

Sign #4: Water Pooling on the Shower Floor

Severity: High — structural problem requiring demo

What You'll See

After a shower, water sits on the floor instead of draining. You might see it pooling at the walls rather than flowing toward the drain. Standing water on the shower floor for extended periods means mold and mildew will develop, grout will degrade faster, and the standing water can work its way under the tile over time.

What Went Wrong Technically

Shower floors must be sloped toward the drain at a rate of ¼ inch per foot — in all directions. That slope exists in two places:

1. In the mortar pre-slope (the layer below the waterproofing membrane). This ensures any water that gets through the tile will drain at the membrane level.
2. In the finished tile surface. The top surface of the tile must also slope ¼ inch per foot toward the drain.

A contractor who sets the shower floor completely flat — or slopes it toward the wrong area — creates a standing water problem that can't be fixed from above.

Can It Be Fixed?

No — not without demo. The slope is built into the mortar bed, not the tile itself. Fixing it means removing all the tile, removing the mortar bed, re-building the pre-slope correctly, re-waterproofing, and re-tiling. It is a full shower rebuild. This is why a bad shower floor slope is one of the most expensive installation mistakes to fix.

Sign #5: Grout Discoloration, Staining, and Mold That Won't Come Clean

Severity: High — may indicate missing waterproofing

What You'll See

Grout joints that are perpetually dark, or that develop black or green mold despite regular cleaning. This is different from normal surface mold (which appears in areas with poor ventilation and responds to cleaning). What we're talking about is mold that grows back within days of cleaning, or discoloration that seems to come from inside the wall rather than the surface.

What Went Wrong Technically

Grout itself is not waterproof. It absorbs water. In a properly installed shower, the waterproof membrane behind the tile catches any water that passes through the grout and routes it to the drain.

When the waterproofing membrane is missing, inadequate, or was improperly installed (wrong thinset type, seams not properly overlapped, corners not properly treated), water soaks through the grout and into the wall assembly. It can't get out. The wall stays wet between uses, creating a perfect environment for mold to grow — not on the surface where you can clean it, but inside the wall where no cleaning product can reach.

Persistent grout darkening can also indicate efflorescence — mineral deposits carried by water migrating through the wall system — which is another sign that water is getting behind the tile where it shouldn't be.

Can It Be Fixed?

If the problem is truly missing or failed waterproofing, no surface treatment will solve it. The shower must be demolished, the wall assembly inspected for mold and rot, remediated as needed, and the shower rebuilt from scratch with proper waterproofing. This is the most serious of the five problems on this list — it can involve structural damage that extends beyond the shower itself.

Summary: Fix or Replace?

Related Guides

• Shower Waterproofing Guide — understand what proper waterproofing looks like before the tile goes in
• Tile Installation Cost in Aurora CO — why the cheapest bid often leads to the most expensive problems
• Large Format Tile Installation — lippage and hollow tiles are especially common with large format when done wrong