Porcelain Paving: A Complete Buyer's Guide

Porcelain paving is a ceramic fired at very high temperature until the body vitrifies — effectively turning glassy. The result is a material with water absorption typically below 0.5 per cent, compared with several per cent for sandstone.

That near-zero porosity is the source of every advantage. Water does not get in, so frost cannot damage it, algae cannot establish in the surface, wine and oil cannot penetrate, and the colour does not change as the slab wets and dries.

It is also the source of the main difficulty. Mortar bonds to porous stone by keying into it. It cannot key into porcelain, which is why a slurry primer on the back of every slab is not optional.

Outdoor porcelain is a different product from indoor tile. It is thicker — 20mm is the standard for patios against 8 to 10mm indoors — and it carries a textured, slip-resistant surface rather than a polished one.

Twenty millimetres is the standard external thickness and is right for pedestrian patios on a full mortar bed. Thicker 30mm slabs exist for pedestal systems and heavier applications.

Slip resistance is expressed as an R rating. R11 is the sensible minimum for a domestic patio in the British climate; R12 and above suits pool surrounds, steps and any sloping area. Do not use an indoor-rated tile outside, however good the price looks.

Large formats — 900 by 600mm and larger — make a space feel bigger with fewer joint lines, but they are heavy, awkward to handle and unforgiving of any unevenness in the bed. Smaller formats are more tolerant and often better on an uneven or awkwardly shaped site.

Porcelain is calibrated, meaning every slab is the same thickness to a fine tolerance. That allows tight, consistent joints of 3 to 5mm and a very flat finished surface, which is a large part of the appeal.

Check whether the range includes matching steps, coping, bullnose edges and a lower-thickness indoor version. Being able to continue the same floor from kitchen to terrace is one of porcelain's strongest features and it needs planning at specification stage.

The build-up is the same as any patio: excavation, compacted MOT Type 1 sub-base, then bedding. What differs is the bedding itself.

Every porcelain slab needs a full mortar bed, typically 30 to 40mm, covering the entire underside. Dabs are unacceptable — voids under a non-porous slab fill with water, and the freeze cycle either cracks the slab or breaks the bond.

A slurry primer must be brushed onto the back of every slab immediately before it is set. This is the bonding layer, and it is the step most often skipped by contractors unfamiliar with the material. Slabs laid without primer come loose within a year or two regardless of how good the bed was.

Falls of about 1 in 80 away from the house apply as with any paving. Because porcelain is impervious, all the water runs across the surface, so getting the fall right matters more than it does on porous stone.

Cutting requires a wet saw with a continuous-rim diamond blade rated for porcelain. Angle grinders with the wrong blade chip the glazed edge badly. Cutting is slower than natural stone and blade wear is a real cost, which is part of why porcelain labour rates are higher.

Brush-in resin jointing compounds are the standard for porcelain. They fill narrow joints reliably, resist weeds, remain slightly flexible and shed water. Two-part slurry-applied products give the most consistent finish on tight joints.

Sand and cement pointing does not work well with narrow porcelain joints — it is difficult to compact into a 4mm gap and it stains the slab face. Where it is used, the surface must be protected and cleaned immediately.

Leave at least 24 hours between laying and jointing so the bed can set undisturbed, and choose a dry spell — resin jointing needs a period without rain to cure.

Edges deserve attention. A bullnose or mitred edge detail at a step or a terrace edge looks considerably better than an exposed square cut showing the unglazed body of the slab.

Porcelain costs more than concrete slabs and more than most Indian sandstone to buy, and it costs more to lay because of the priming, the full bed and the slower cutting. A porcelain patio is realistically the most expensive of the common options.

Against that, it needs no sealing, ever, which removes a recurring cost that sandstone and limestone carry every three to five years. It resists algae and black spot far better, so annual cleaning is lighter work. And it does not fade, so it looks the same in year fifteen as in year one.

The most common regret we hear is not the cost but the specification — choosing a slab that looked good in a showroom under artificial light and reads as cold and grey under an overcast Essex sky. Always view samples outdoors, wet and dry, on the day.

Maintenance is genuinely minimal. Sweep it, wash it occasionally with warm water and a mild detergent, and clear leaves promptly. It needs no sealing and no re-jointing.

Where a film of green algae appears — usually in permanently shaded areas — a standard patio cleaner removes it easily because nothing has penetrated the surface.

Avoid dragging metal furniture across it, which can leave metal transfer marks. These lift with a proprietary cleaner but are irritating.

The one thing porcelain will not tolerate is a poorly built base. It is a rigid, brittle material with no flexibility. Where the ground beneath moves, natural stone might tolerate it and porcelain will crack. Spend the money on the groundwork.