What is the minimum tile size RCB specifies for bathrooms?

Our standard specification calls for a minimum of 300x300mm (30x30cm) for both floor and wall tiles. This is not arbitrary — smaller tiles mean more grout lines, more maintenance, and a more dated appearance. For contemporary bathrooms we typically specify 600x600mm or larger on walls, and 600x600mm on floors where slip ratings permit.

Do I need different tiles for the floor and walls?

Yes. Floor tiles must carry an appropriate slip rating (R10 or above for wet areas like showers, R9 as a minimum for bathroom floors). Wall tiles carry no such requirement, but they must be rated for wet areas and should not be used on floors regardless of appearance. Many clients choose matching or complementary ranges — a large-format wall tile paired with a smaller mosaic floor tile — but using a wall-rated tile underfoot is a compliance and safety risk.

Is porcelain better than ceramic?

For most bathrooms, yes. Porcelain is denser, less porous, harder wearing and more resistant to water absorption than standard ceramic. The difference matters most on floors and in wet rooms. On walls in a standard bathroom, a good-quality ceramic performs perfectly well and costs less. The real risk is using a low-density ceramic tile on a floor and expecting it to last — it will not.

How much should I budget for bathroom tiles?

As a guide: budget tiles run £25–£40 per m², mid-range £40–£80 per m², and premium or natural stone £80–£150 per m² and above. However, the tile cost is only part of the picture. Installation — including adhesive, grout, waterproofing membrane, and labour — typically adds £35–£60 per m² on top. Do not buy budget tiles and expect a luxury result: the two are incompatible.

What slip rating do I need for a shower floor?

For a shower floor or wet room, you need a minimum R10 rating under the DIN 51130 standard. R9 is acceptable for a standard bathroom floor where the area is not directly wet underfoot. R11 and above is used in commercial wet environments. Anything rated R9 or below on a shower floor is a genuine slip hazard and should not be installed. Always check the product datasheet, not just the tile supplier's marketing description.

Does grout colour really matter that much?

More than most people expect. Grout covers roughly 10–15% of a tiled surface. A light tile with dark grout creates a grid effect that emphasises tile edges — often undesirable with large-format tiles. A contrasting grout can also make dirt and discolouration more visible over time. Most of our projects use a grout matched closely to the tile body for a clean, low-maintenance result. Mosaic tiles and feature areas are exceptions where contrast grout can work well intentionally.

How to Choose Bathroom Tiles

The Enemy in the Tile Industry: Confusion by Design

The tile industry makes a lot of money from confused buyers. Marketing terms like “premium porcelain feel” or “stone effect” are not technical specifications — they are sales language. A tile with a stone effect surface can be a dense, durable porcelain or a thin, fragile ceramic that will crack under normal use. The packaging often will not tell you the difference.

At RCB, we specify tiles the same way a structural engineer specifies concrete: by performance characteristics, not aesthetics. Aesthetics come second. Here is the framework we use.

Porcelain vs Ceramic vs Natural Stone

These three categories behave fundamentally differently. Choosing the wrong category for the location is the single most common tiling mistake in domestic bathrooms.

Porcelain

Fired at higher temperatures than ceramic, porcelain has a water absorption rate below 0.5%. It is harder, denser and significantly more durable. Suitable for floors and walls. Available in large formats up to 1200x2400mm. The standard material for any wet room or shower enclosure. More expensive than ceramic but worth it on floors.

Ceramic

Softer, more porous and easier to cut than porcelain. Water absorption can reach 10% or more in cheaper products. Perfectly adequate for bathroom walls in non-wet-area applications. Not recommended for shower floors or wet room floors. Lower cost per m² but higher lifetime cost if used in the wrong location.

Natural Stone

Marble, travertine, slate and limestone are the most common bathroom choices. Each has unique characteristics and maintenance requirements. Natural stone is porous and must be sealed on installation and periodically thereafter. Limestone and travertine are particularly vulnerable to acidic cleaners. Beautiful when done correctly; a maintenance burden when not. Budget £80–£150/m² for decent natural stone, plus sealing costs.

Size Matters: The RCB Standard Specification

Our minimum specification is 300x300mm for any bathroom tile application. This is not a style preference — it is a practical baseline. Smaller tiles create more grout joints, which means more surface area for mould and bacteria, more maintenance, and a more cluttered visual result.

300x300mm (30x30) — minimum acceptable. Commonly used in smaller bathrooms and budget renovations. More grout lines than larger formats.
600x600mm (60x60) — the sweet spot for most residential bathrooms. Large enough to feel contemporary, small enough to work in tighter spaces with less cutting waste.
600x1200mm and above — large format. Increasingly popular for wet rooms and open-plan bathrooms. Fewer grout lines, cleaner aesthetic. Requires a flatter substrate and experienced installation.
Mosaic tiles (typically 20x20mm to 50x50mm) — decorative use, feature areas, shower floors where smaller format aids drainage gradient. More grout = more maintenance. Do not tile an entire bathroom in mosaic unless you enjoy cleaning.

RCB Standard Spec Note

Where clients specify mosaic tiles for entire floors, we flag the maintenance implications and document their preference as a client choice. Our default recommendation is 600x600mm rectified porcelain for floors and 300x600mm or 600x600mm for walls, matched to room proportions.

Slip Rating (R-Value) for Wet Areas

This is where decisions get serious. The DIN 51130 standard classifies floor tiles by their slip resistance under working conditions. The R-value is not a marketing claim — it is a measured result. Using the wrong R-value on a shower floor is a safety and liability issue.

Standard bathroom floor (dry areas). Not suitable for showers.

R10

Shower floors, wet rooms, areas with direct water contact. Minimum for wet areas.

R11+

Commercial wet areas. Sometimes used in residential wet rooms for added safety.

Many budget tiles sold in UK retail stores carry an R9 rating but are marketed for “bathroom use.” This is technically not incorrect — a dry bathroom floor is an R9 application — but it is misleading for anyone planning a walk-in shower. Always read the product datasheet.

Cost Guide: What You Are Actually Paying For

Tile cost per m² is only one part of the equation. Installation, substrate preparation, waterproofing and adhesive can easily double the headline tile cost. Here is a realistic breakdown.

Budget

£25 – £40 /m²

Standard ceramic wall tiles, basic porcelain floor tiles. Acceptable for rental properties and secondary bathrooms. Limited size options, fewer finishes.

+£35–£50/m² installation

Mid-Range

£40 – £80 /m²

Good-quality rectified porcelain, large-format options, wider finish range. The best value category for most owner-occupied homes.

+£40–£55/m² installation

Premium

£80 – £150+ /m²

Natural stone, designer porcelain, book-matched slabs. Adds genuine value when the rest of the bathroom specification supports it. Wasted if paired with budget sanitaryware.

+£50–£70/m² installation

Grout Colour Matters More Than You Think

Grout covers approximately 10–15% of a tiled surface. It is not an afterthought — it is a design decision with long-term consequences. Most people choose grout last, under time pressure, without having seen it next to the tile in the actual light conditions of the room. This is how you end up with a bathroom you cannot stand looking at six months later.

Matched grout (same tone as tile): the cleanest result with large-format tiles. Minimises the visible grid pattern. Makes the room feel larger. Slight discolouration over time is less visible.
Light grout on light tiles: works well but requires more maintenance. Shows limescale and mould earlier. Epoxy grout or anti-fungal additive is advisable in shower enclosures.
Dark grout on light tiles: high contrast, intentional grid effect. Works well with metro tiles and feature walls. Shows calcium deposits from hard water in London very quickly.
White grout in a London bathroom: nearly always the wrong choice. Greater London has extremely hard water. White grout in a shower goes grey within 12 months without intensive maintenance.

Wall Tiles vs Floor Tiles: Different Requirements

The terms “wall tile” and “floor tile” are not interchangeable. The distinction is a structural one.

Wall Tiles

No slip rating required
Can be lighter and thinner (6–10mm)
Lower PEI hardness rating acceptable
Can include glazed surfaces not suitable underfoot
Must still be rated for wet area use in bathrooms

Floor Tiles

Must carry R9 minimum slip rating (R10 in wet areas)
Typically 8–12mm thick for durability
PEI rating of 4+ for residential floors
Must handle foot traffic and cleaning chemicals
Some wall tiles cannot legally be used on floors — check the datasheet

Where People Waste Money — and Where They Should Invest

Where budgets get wasted

Premium tiles on a poorly prepared substrate — the substrate telegraphs through and the tile cracks or lifts

Designer mosaics on entire floors of large bathrooms — excessive grout maintenance and visual noise

Natural stone in a rental property — wrong audience, wrong maintenance expectation

Matching tiles from different batches — colour variation is visible and unfixable

Budget adhesive behind expensive tiles — false economy that leads to costly re-tiling

Where to invest properly

Substrate preparation — a flat, solid, waterproofed base makes every tile look better and last longer

Waterproofing membrane in shower enclosures and wet rooms — not optional

Large-format porcelain on floors — fewer grout lines, longer life, better appearance

Good-quality flexible adhesive and grout — small cost relative to the tile budget

An extra 10% tile overage — for cuts, breakages, and future repairs from matching batches

How to Choose Bathroom Tiles — What Most People Get Wrong