Porcelain Patio Slabs: Pros, Cons and Costs

What porcelain is good at

Porcelain paving is fired at very high temperature and has a water absorption below 0.5 percent. That single figure explains almost every advantage it has. It does not soak up water, so it does not stain from wine, barbecue fat or leaf tannin, it does not host moss and algae the way porous stone does, and it is unaffected by frost.

It is also dimensionally consistent. Every slab is the same thickness and the same size, so the finished patio has tight, even joints and a flat surface. On a big terrace, that consistency is very visible.

What porcelain is not good at

It is unforgiving to lay. It cannot be spot bedded, cannot be tapped down into a dry mix, and needs a full wet mortar bed with a slurry primer on the back of every slab. Cutting requires a wet saw with a diamond blade, and it chips if you rush.

It is cold and hard underfoot compared with sandstone, which some people dislike barefoot in summer. It looks contemporary, so it can sit awkwardly against a period cottage in Farnham or Crookham Village where riven stone is the honest choice.

And it does nothing to hide a bad base. Any movement in the sub-base cracks the mortar joints straight away, because there is no give in the material.

What porcelain actually costs fitted

The slabs themselves are only about a third of the cost. Laying is where the money goes.

Slip resistance: the number that matters

Look for the R rating. For a domestic patio in the UK climate, R11 is the sensible minimum and R11 or R12 is what we specify as standard. R9 and R10 finishes are intended for interior use and become genuinely slippery outdoors when wet, particularly in shade.

Ignore the marketing phrase anti slip on its own. Ask for the R value and the pendulum test value if the supplier has one. A shaded north facing terrace in a wooded garden should be at the higher end regardless of what the brochure photograph looks like.

How porcelain has to be laid

Excavate 200 to 250mm, compact 100 to 150mm of MOT Type 1, then lay each slab on a full bed of 4:1 sharp sand and cement, 35 to 50mm thick, with a cement based slurry primer painted onto the back of the slab immediately before it goes down.

The primer is the step cheap installers skip. Without it, porcelain simply does not bond to mortar, and slabs come loose within a year or two even though the base is fine. If a quote does not mention slurry priming, the installer either does not know or is not doing it.

Joints should be 5mm minimum and filled with a proper two part or resin jointing compound, not brushed in sand. Falls should be 1 in 80 away from the house, with the finished surface at least 150mm below the damp proof course.

Maintenance and lifespan

Sweep it, wash it with warm water and a mild detergent a couple of times a year, and keep leaf litter off. Porcelain needs no sealing, ever, and sealing it can actually cause a hazy film.

Expect 30 years plus from the material itself. In practice the joints and the base decide the life of the patio, which is why we specify resin jointing and a full mortar bed rather than the cheaper alternatives.

If you want a porcelain terrace priced properly, with the base, primer and jointing all itemised, call 07538 218723 or use our quote page and we will survey and put it in writing.