Porcelain Patio Installation: How It Should Be Laid

Sandstone and limestone are porous. Mortar soaks into the back of the stone and forms a mechanical key. Porcelain is fired at high temperature until it is almost glass-like, which is what makes it stain resistant and easy to clean. The same property means mortar sits against it rather than bonding into it.

A primer brushed onto the back of every slab just before it is laid gives the mortar something to hold. Missing out this step is the most common reason porcelain slabs are found rocking or hollow.

The patio area is dug out, a compacted sub-base is built in layers, and levels are set so rainwater runs away from the house. Porcelain sheds water fast because it absorbs so little, so falls and a plan for where that water goes are essential. Our patio build guide sets out the full build-up.

Each slab is set on a complete bed of mortar, not on a few dabs. Spot bedding leaves voids underneath. With a thin, rigid material like porcelain, a void under a corner is enough to crack a slab when someone steps on it or a heavy pot is placed there.

Slabs are tapped down to level with a rubber mallet and checked in both directions as work goes on, keeping joint widths consistent.

Porcelain is very hard and chips easily if cut with the wrong blade. Installers need a diamond blade designed for porcelain and a steady wet cut. Clean cuts around drains, steps and edges are one of the quickest ways to tell a careful installation from a rushed one.

Joints are filled once the bed has set. A jointing compound suitable for porcelain is used, and the surface is kept clean as work goes, because residue left to cure on a smooth porcelain face is hard to remove. Full, well finished joints stop water and weeds getting under the slabs.

Timing depends on the size of the patio, the access, how much old paving or soil has to come out, and the weather, since mortar should not be laid in frost or heavy rain. We give a timetable with the written quote after a free site visit, and tell you when the patio is ready to walk on and when it can take furniture.

When the job is done, walk the patio and tap slabs gently with your foot; a hollow sound can mean a void underneath. Joints should be full and even, cuts clean and the surface free of mortar haze. Water should run off without standing in puddles.