How to Lay a Patio

Laying a patio: the quick version

A patio that stays flat and drains for decades comes down to four things: a firm, well-compacted sub-base; slabs laid on a full bed rather than spot dabs; an even drainage fall away from the house; and clean, well-filled joints. Get those right and almost any slab will perform. Get the dig or the bed wrong and even the best porcelain will rock, crack and puddle. This guide walks through every stage — setting out, fall, excavation, sub-base, bedding, laying and pointing — and the planner above turns your measurements into quantities you can order or quote from.

Tools, materials & safety

Planning & setting out

Mark the patio with pegs and string, then check it is truly square by measuring the diagonals — they should be equal. Dry-lay a few slabs to confirm the size works with whole slabs and a sensible joint, so you cut as little as possible. Where the patio meets the house, the critical rule is the damp-proof course.

1. Decide the finished level first, then work down: it must end up at least 150 mm (two brick courses) below the damp-proof course where it meets the house.
2. Set string lines to your finished slab level, then set the fall into those lines so water runs away from the wall.
3. Square the area by measuring diagonals — equal diagonals mean square corners.
4. Dry-lay to check the layout falls on whole slabs and even joints before you dig.

Calculating the fall (drainage)

A patio must never be dead level — it needs a gentle, even slope so rain runs off instead of puddling or pooling against the house. Use about 1:80 (12.5 mm per metre) for textured slabs and 1:60 (≈16.7 mm per metre) for smooth ones. Multiply the drop per metre by the longest run to get the total fall, then build it into your string lines and sub-base. Tap the options below to see how the gradient changes.

Need the exact figure? The patio fall calculator works out the total drop across your run for any ratio.

The fall, bedding and drainage rules change with the slab you choose. Pick your material below to see the recommended fall, whether you need a slurry primer, permeable alternatives and the key compliance points.

Excavation & sub-base

The sub-base is the structural heart of the patio — almost every failure (sinking, rocking, puddles) traces back to a thin or poorly compacted base. Strip off all turf and topsoil and dig to firm subgrade, allowing for sub-base + bedding + slab + the fall.

1. Dig out turf, topsoil and any soft spots until you reach firm subgrade. Heel-test it — if your heel sinks in, dig deeper or compact harder.
2. On clay or soft/made-up ground, lay a woven geotextile membrane over the subgrade (300 mm laps) so the stone can't punch into the clay.
3. Spread MOT Type 1 and compact it in 75–100 mm layers with a plate compactor, blinding with a little sand if the surface is open.
4. Aim for 100 mm of compacted sub-base on good ground, 150 mm on clay — and keep the fall consistent through the base.

For full depths, Type 1 vs Type 3 permeable, compaction and tonnage, see the sub-base & MOT Type 1 specifications guide.

Bedding & laying the slabs

Lay slabs on a full bed — a continuous layer of wet mortar (or, for some concrete slabs, screeded sharp sand). The single most common mistake is the “five-spot” dab method: five blobs of mortar under each slab. It leaves hollow voids that hold water, crack slabs under load and cause rocking. A full bed supports the whole slab.

1. Mix a fairly dry, workable bedding mortar (around 4:1 sharp sand to cement). Lay enough bed for one slab at a time.
2. For porcelain and natural stone, brush a slurry primer onto the back of each slab so it bonds to the mortar.
3. Lay the key slab first — the highest corner against the house — and tap it level to the string lines with a rubber mallet.
4. Work outward from the key slab, keeping consistent joint widths with spacers and checking levels and the fall constantly.
5. Cut edge and obstacle slabs with a diamond blade. Keep off the slabs for ~24 hours while the bed sets before pointing.

Pointing & jointing

Pointing seals the joints so the patio locks together, sheds water and resists weeds. The right method depends on your joint width. For most modern patios a brush-in jointing compound is the easiest, most durable choice — and the only sensible option for porcelain.

Aftercare, curing & sealing

• Keep off the patio for 24 hours after laying and ideally 24–48 hours after pointing before furniture or heavy use.
• Cover with sheeting if rain or frost is forecast while the mortar and joints cure.
• Seal natural stone and concrete (not usually porcelain) once fully dry to resist staining and algae.
• Keep it clean with a stiff brush and occasional wash; avoid pressure-washing fresh joints.

How much does it cost to lay a patio?

Cost depends mostly on the slab you choose, the size and shape of the patio, and how much groundwork is involved. As a guide, DIY material costs run from about £40 per m² for plain concrete to £95 per m² for premium porcelain; having it supplied and laid by a professional roughly doubles that. Labour only (you supply the materials) is typically £40–£70 per m², or £150–£250 a day for a two-person team.

What pushes the price up: poor access (slabs and spoil barrowed a long way), heavy clay or soft ground needing a deeper sub-base and geotextile, removing an old patio, and muck-away (skip hire and tip fees for the dug-out spoil). Run the planner above for your area and quantities, then use the patio build-up calculator to price materials precisely before you buy or compare quotes.

Patio variations & common questions

Frequently asked questions