How a porcelain patio is laid, step by step

Planning the layout before anything is dug

Porcelain slabs are cut to tight tolerances, which means the layout should be set out with cuts in mind. We plan where full slabs will sit, where cuts will fall, and how the patio meets walls, doors and lawn, so that small slivers of cut slab do not end up at the most visible edge.

Falls are decided at this stage too. Porcelain sheds water quickly because it absorbs almost none, so the patio needs a gentle, consistent fall away from the house towards a lawn, gravel margin or drain.

Building the base

The ground is excavated and a compacted sub-base is laid in layers. Because porcelain is rigid and flat, any settlement underneath shows up as a rocking or lipped slab far more obviously than it would with riven stone. A firm, well-compacted base is not optional.

Where the patio sits against the house, the finished level must stay safely below the damp-proof course, and air bricks must be left clear.

Priming the back of every slab

This is the step that separates a porcelain patio that lasts from one that starts rattling within a year. The back of each slab is coated with a bonding primer, a slurry that gives the mortar something to key into. Without it, the smooth underside can let go of the bed, leaving a hollow slab that clicks underfoot and eventually cracks.

Laying on a full mortar bed

Each slab goes down onto a full, solid mortar bed rather than a few dabs at the corners. Spot bedding leaves voids where water can collect and freeze, and a void under a rigid slab is a weak point waiting for a dropped pot or a heavy barbecue.

Slabs are tapped down to level and checked against their neighbours for lipping. Spacers keep joint widths even, which matters with porcelain because the straight lines make any wandering joint obvious.

Cutting and finishing edges

Porcelain is very hard and needs a proper diamond blade to cut cleanly; chipped cut edges are a sign of the wrong tools. Exposed edges at steps or raised areas are finished neatly, and cuts are kept to the planned positions.

Jointing

Joints are filled once the bed has set, typically with a jointing compound designed for porcelain. Care is taken to keep the slab surface clean during jointing, because residue left on porcelain is harder to remove later.

Looking after it afterwards

Porcelain does not need sealing, and a sweep and occasional wash with water keeps it looking right. The areas to watch over time are the joints, which should be checked for gaps after the first winter.

Common porcelain faults and what causes them

Most problems with porcelain patios trace back to one of three things: no primer on the slab backs, spot bedding instead of a full bed, or a base that was never compacted properly. The symptoms are hollow-sounding slabs, a click or rock underfoot, raised lips between neighbouring slabs, and eventually cracked corners.

If you already have a porcelain patio showing these signs, the affected slabs usually need lifting, cleaning off and relaying on a primed full bed. Filling the joints again will not stop a slab moving if there is nothing solid under it.