10 Bathroom Tile Mistakes I See Every Month (and How to Avoid Them)

I have been tiling bathrooms for 44 years, and the same mistakes keep appearing in homes across Bromley and South East London. Some are made by homeowners during the planning stage. Some are made by tilers during installation. Some are made by both.

This is the list I wish every homeowner had before they started a bathroom renovation. None of these are difficult to avoid if you know what to look out for.

3D cube floor, Beckenham. The setting-out for a pattern like this is unforgiving — one tile in the wrong position breaks the optical illusion entirely. Mistakes in patterned tiling are visible in a way they are not in straight lay. Pattern tiling service

Mistake 1: Skipping the waterproofing

The mistake: Installing tiles in a shower or wet area without first applying a tanking membrane to the substrate.

Why it happens: The tanking is invisible once the tiles are on. The customer cannot see whether it was done. The tiler can save half a day and a hundred pounds in materials by skipping it. The bathroom looks perfect on the day of completion.

What goes wrong: Grout is not waterproof. Over time, water migrates through grout joints and reaches whatever is behind the tiles. Without tanking, that “whatever” is plasterboard or timber, which absorbs the moisture and starts to decay. By the time you can see damage from the front of the tiles, the wall behind is significantly compromised.

The fix: Insist on tanking before any tile goes on in a shower area. Ask the tiler to name the product they will use (Mapelastic, BAL Tank-it, Schluter Kerdi membrane, or similar). A tiler who hesitates or vague-replies is a tiler who does not normally tank. See what is tanking.

Mistake 2: Choosing the wrong tile for the application

The mistake: Using a ceramic floor tile in a bathroom. Using a polished tile on a shower floor. Using a wall tile on a floor.

Why it happens: Tiles are sold by appearance, not by use case. The tile that catches your eye in the showroom may not be rated for your application.

What goes wrong: Ceramic floor tiles absorb moisture in wet areas and deteriorate over years. Polished tiles become dangerously slippery when wet. Wall tiles cannot handle floor load and crack under foot traffic.

The fix: Check the slip rating (R10 minimum for bathroom floors, R11 for shower floors). Check water absorption (porcelain rating below 0.5%). Confirm the tile is rated for the intended use. A reputable tiler will ask these questions before installing. See porcelain vs ceramic tiles and matte vs gloss tiles.

Mistake 3: Grouting the floor-to-wall joint

The mistake: Filling the joint where the floor tile meets the wall tile with grout instead of silicone.

Why it happens: It looks neater. It maintains the appearance of consistent grout throughout the bathroom. The customer often asks for it.

What goes wrong: The floor and wall move independently. They expand and contract at slightly different rates with humidity and temperature changes. A grouted joint is rigid — it cannot absorb this movement. Within months, the grout cracks. Once cracked, water gets in, and the base of the wall starts to deteriorate.

The fix: Always silicone the floor-to-wall joint. A colour-matched silicone is barely visible against the grout colour. The joint must be flexible. This is non-negotiable. See why tiles crack.

Mistake 4: Inadequate substrate preparation

The mistake: Tiling onto a wall or floor without checking that the substrate is sound, flat, and stable.

Why it happens: Substrate work is unglamorous and invisible. The tiler can save time by skipping the prep and getting straight to the visible work.

What goes wrong: Tiles installed over hollow plaster eventually de-bond. Tiles installed over an uneven floor show as visible lippage. Tiles installed over a moving substrate crack within months.

The fix: Tap every wall before tiling. Hollow plaster needs replacing. Run a long straightedge over the floor. Anything more than 3mm in 2 metres needs levelling compound. Insist your tiler does this before quoting, not after starting. See tile installation guide.

Mistake 5: Wrong adhesive specification

The mistake: Using a basic C1 adhesive for porcelain, large format tiles, wet areas, or underfloor heating.

Why it happens: Cheaper adhesive saves money. Untrained tilers may not know the difference between adhesive grades.

What goes wrong: Tiles de-bond. Large format tiles develop hollow spots. Tiles over UFH crack from thermal cycling. Wet area tiles fail at the substrate.

The fix: Porcelain needs C2 or better. Large format needs C2 with full back-buttering. UFH needs flexible C2S1 or C2S2. Wet areas need waterproof-rated adhesive. Ask the tiler to name the specific product and check the datasheet. See tiling over underfloor heating.

Mistake 6: Choosing too many different tiles

The mistake: Using three or more different tile types in one bathroom — floor tile, main wall tile, feature wall tile, niche tile, splashback tile.

Why it happens: Pinterest. Magazines. The desire to “do something interesting” with multiple design elements.

What goes wrong: Visual chaos. The bathroom feels busy and unrestrained. Each tile competes for attention. The room reads as decorated rather than designed.

The fix: Use one or two tile types maximum. Create variation through pattern, finish, or layout rather than entirely different materials. The most striking bathrooms are typically the most restrained. See tile drenching trend for the opposite approach.

Mistake 7: Wrong grout colour

The mistake: Choosing white grout in a wet area. Choosing a strongly contrasting grout that highlights every imperfection. Choosing a grout colour without seeing how it dries.

Why it happens: Grout is an afterthought in most renovations. It is selected from a small chart at the end of the planning process.

What goes wrong: White grout in showers discolours within a year. Strongly contrasting grout shows every cleaning streak and grout line variation. Grout colours look completely different wet versus dry.

The fix: For wet areas, use epoxy grout or a stain-resistant grout. Match grout to tile or go one shade darker for forgiveness. Always test grout colour on a sample before committing to the bathroom. See grout colour guide.

Mistake 8: Stopping wall tiles partway up

The mistake: Tiling shower walls only to 1800mm or 2000mm height instead of full ceiling height.

Why it happens: Saves tiles, saves labour, follows the height of standard tile sheets.

What goes wrong: Steam from the shower rises above the tile line and hits the painted wall above. Within a year, the paint peels, the plaster softens, and you are repainting annually. The visual break also makes the room feel less finished.

The fix: Tile shower walls to full ceiling height. The additional cost is modest. The protection and visual completeness are significant. See shower tile ideas.

Mistake 9: Bad setting-out at the start

The mistake: Starting tiling from a corner without working out where the cut tiles will fall, where the pattern will land, and whether the layout is balanced.

Why it happens: Setting out takes time and does not produce visible work. Some tilers skip it and start laying immediately.

What goes wrong: Narrow sliver cuts at one wall and full tiles at the other. Patterns that fall awkwardly across visible surfaces. Cuts that draw the eye to the wrong places. Layouts that look unbalanced even though no individual tile is wrong.

The fix: Setting out is non-negotiable. A good tiler spends as long planning the layout as laying the first row. They mark datum lines, dry-lay the pattern, check balance at opposite walls, and adjust before any adhesive is mixed. If your tiler is laying tiles within the first hour of arriving, they have not set out properly.

Mistake 10: Hiring on price rather than evidence

The mistake: Choosing the tiler with the cheapest quote without checking their work, qualifications, or specifications.

Why it happens: Price comparison is easy. Quality assessment is harder.

What goes wrong: Cheap quotes typically omit the things that matter — substrate preparation, tanking, correct adhesive specification, movement joints. The tiles go up faster and the visible result looks fine. The job fails 6-18 months later, after the tiler has been paid and gone.

The fix: Check qualifications (City and Guilds, NVQ Level 2). Ask to see photos of recent work. Ask to speak to a previous client. Ask the technical questions: what adhesive will they use, will they tank wet areas, how will they handle the floor-to-wall joint. The answers reveal more than the price. See how to choose a tiler.

What this list has in common

Every mistake on this list comes from one of two sources: cutting corners that the customer cannot see, or choosing on appearance without understanding the technical requirements.

Both are avoidable with one piece of discipline: ask the technical questions before work starts. A competent tiler will answer them clearly and confidently. An inexperienced or corner-cutting tiler will be vague.

For a free site visit, technical assessment, and a quote that includes all the right things, get in touch. I will tell you exactly what your bathroom needs and what the cost includes. See also: how to choose a tiler | how to spot good tiling | tile installation guide