Porcelain Tiles: Everything You Need to Know

Porcelain tiles have become the default choice for kitchen and bathroom floors across Bromley and South East London, and it is easy to see why. They are dense, hard-wearing and shrug off everything from underfloor heating to a daily soaking in a shower enclosure. This guide explains what porcelain tiles actually are, how to read the ratings printed on the box, and where each type belongs, so you buy the right tile once rather than paying to put it right later.

What makes a tile “porcelain”?

The line between porcelain and ordinary ceramic is not a marketing label, it is measured. Under the international standard ISO 13006 (mirrored by the British and European standard BS EN 14411), a tile is classed as porcelain when its water absorption is 0.5% or less by weight, which puts it in the dense BIa group. Ordinary ceramic wall tiles often absorb 10% or more.

Porcelain reaches that figure because it is pressed from a finer, refined clay and fired hotter, usually around 1,200 to 1,300 degrees Celsius. The result is a vitrified body that is close to non-porous. That very low absorption is the reason porcelain resists frost, staining and moisture far better than standard ceramic, and why it can be used outdoors and in wet rooms where a cheaper ceramic would eventually fail.

Porcelain vs ceramic: the key differences

Both tiles start as clay, but the recipe and firing differ. Porcelain is denser, heavier and harder, which makes it more durable and frost-proof but also tougher to cut. Ceramic is softer, lighter and cheaper, and is perfectly good for walls and low-traffic areas. If you want the full breakdown, our guide to porcelain versus ceramic tiles compares them job by job. As a rule of thumb: porcelain for floors, wet areas and outdoors, ceramic for walls where budget matters.

Understanding PEI ratings and where to use each

Glazed porcelain carries a PEI rating (from the Porcelain Enamel Institute) that tells you how well the surface resists wear from foot traffic. It runs from 0 to 5:

PEI 0 to 1: walls only, no floor use.
PEI 2: light residential floors such as bedrooms and en-suites.
PEI 3: most domestic floors, including bathrooms and living areas.
PEI 4: heavy domestic and light commercial use, ideal for hallways, kitchens and utility rooms.
PEI 5: heavy commercial traffic such as shops and entrances.

For a typical home floor, aim for PEI 3 or 4. A busy kitchen or hallway that catches grit from the garden will thank you for a PEI 4.

Glazed, full-body and rectified porcelain

There are three terms worth knowing before you shop. Glazed porcelain has the colour and pattern printed on a surface glaze, which allows realistic wood and marble effects. Full-body (or through-body) porcelain has the colour running all the way through, so a chip is far less visible, which suits heavy-use and commercial floors. Rectified tiles have edges that are mechanically ground perfectly straight after firing, letting you lay tight grout joints of around 2 to 3mm. Rectified edges are almost essential for large-format tiles, where any size variation would show.

Polished, matt and textured finishes

Finish is not just about looks, it decides how safe the floor is underfoot. Slip resistance is measured two ways in the UK: the R rating (R9 to R13, from a ramped test) and the pendulum test value, or PTV. The Health and Safety Executive treats a floor with a PTV of 36 or above as a low slip risk. Polished porcelain looks stunning but becomes slippery when wet, so it belongs in dry, low-traffic rooms. For a bathroom, wet room or kitchen floor, choose a matt or lightly textured tile rated around R10 to R11, or a PTV of 36 plus. You can read the HSE’s own guidance on assessing floor slip resistance if you want the technical detail.

Porcelain tiles outdoors: 20mm paving

Because porcelain is frost-proof, it has taken over from natural stone for patios. Outdoor porcelain is made in a thick 20mm format designed to be laid on a full mortar bed with a priming slurry on the back of each slab, so it bonds properly and drains. It comes with a textured anti-slip finish, usually R11, to stay safe when wet. Many ranges are sold in a 9 or 10mm indoor thickness and a matching 20mm outdoor slab, so you can run the same tile from a kitchen straight out onto the patio for a seamless inside-outside look.

Cutting and fitting porcelain

This is where porcelain earns its reputation. Because it is so hard and dense, it needs the right tools. Straight cuts can be scored and snapped with a good manual cutter fitted with a porcelain wheel, but large-format tiles, mitres and awkward angles call for an electric wet saw with a diamond blade. Holes for pipes and taps need a diamond hole saw, not a standard tile bit. Fitting-wise, porcelain wants a flexible (S1-rated) adhesive, full coverage with back-buttering so there are no voids, and a tile-levelling system on big formats to prevent lippage where one edge sits proud of the next. This is the point at which many homeowners decide the job is worth handing to a professional tiler.

Cost and value

Porcelain typically costs a little more per square metre than ceramic, and the labour rate is marginally higher because it is slower to cut. Set against a lifespan measured in decades, low maintenance and the fact that it will not stain or absorb water, it is usually the better long-term value for any floor, wet area or outdoor space. If you are weighing up your options for a specific room, our tiling guides and cost advice can help you plan the job.

Frequently asked questions

Are porcelain tiles better than ceramic?

For floors, wet areas and outdoors, yes. Porcelain is denser, harder and effectively waterproof, so it lasts longer and copes with frost and heavy traffic. For walls and lower-traffic rooms, ceramic is lighter, cheaper and perfectly capable.

Do porcelain tiles need sealing?

The tile body itself does not, because it absorbs almost no water. Glazed porcelain never needs sealing. A polished or unpolished natural-finish porcelain can benefit from a one-off protective treatment, and cement-based grout lines should always be sealed to keep them clean.

Can you use porcelain tiles on walls?

Yes, but they are heavy, so the wall and adhesive must be up to it. Plasterboard has weight limits, and large-format porcelain often needs a tile backer board and a stronger adhesive to hold securely.

Are porcelain tiles good for underfloor heating?

They are one of the best choices. Porcelain conducts and holds heat well and is dimensionally stable, so it will not be damaged by the warming cycle. Use a flexible adhesive and grout rated for underfloor heating.

Do porcelain tiles crack easily?

No. They are among the hardest floor finishes available. When a fitted porcelain floor does crack, the cause is almost always movement in the substrate below rather than the tile itself, which is why proper preparation and a flexible adhesive matter.

Can you lay porcelain outside in the UK?

Yes. Porcelain is frost-proof, so British winters are no problem. Use the 20mm outdoor format, lay it on a full mortar bed with a priming slurry, and choose an anti-slip R11 finish for a safe patio.

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