How deep should you dig for a patio?

For a typical garden patio, dig to roughly 150–175 mm: about 100 mm of compacted MOT Type 1 sub-base, 30–40 mm of bedding (mortar or sharp sand), plus the slab thickness (20 mm porcelain, ~22 mm natural stone, up to 38–50 mm concrete). On heavy clay or soft ground increase the sub-base to 150 mm and add a geotextile membrane, so the dig becomes around 200–225 mm. The patio planner on this page works out the exact dig depth for your slab and ground.

What is the best base for a patio?

The reliable build-up is: firm, compacted subgrade → geotextile membrane on clay or soft ground → 100–150 mm of MOT Type 1 sub-base compacted in 75–100 mm layers → a full mortar or sharp-sand bedding layer → your slabs. Porcelain and natural stone must go on a full wet mortar bed (never sand or spot dabs).

Can you lay a patio without cement?

You can lay some concrete or natural-stone slabs on a screeded sharp-sand bed over a compacted MOT Type 1 sub-base, then joint with kiln-dried sand or a brush-in compound. It is quicker and cheaper, but slabs are more likely to rock or settle and it is not suitable for porcelain, which needs a full wet mortar bed and a slurry primer. For a long-lasting patio, a mortar bed is the safer choice.

What fall does a patio need for drainage?

Aim for a fall of about 1:80 (12.5 mm drop per metre) for textured or riven slabs, or 1:60 (around 16.7 mm per metre) for smooth slabs that shed water more slowly. Never lay a patio dead level, and always fall it away from the house — toward a lawn, border, gravel margin or drainage channel. The patio fall calculator works out the total drop across your run.

How far below the damp-proof course should a patio be?

Where a patio meets the house, the finished paving must sit at least 150 mm — two brick courses — below the damp-proof course (DPC), and fall away from the wall. Paving that bridges or sits above the DPC lets damp track into the masonry, so keep the clearance and add a drainage channel at the wall if you can't drop the level enough.

Can you lay a patio on grass or soil?

Not directly. Grass and topsoil are soft, full of organic matter and will rot, compress and let slabs sink. Always strip off the turf and topsoil, dig down to firm subgrade, then build up a compacted MOT Type 1 sub-base and bedding layer before laying. The dig and sub-base are what make a patio last.

How long does it take to lay a patio?

A competent DIYer can lay a small 10–20 m² patio over a weekend or two: a day or so for setting out and excavation, a day for the sub-base and bedding, then laying and pointing. Allow extra time for curing — keep off the patio for 24 hours after laying and ideally 24–48 hours after pointing before heavy use.

How much does it cost to lay a patio in the UK?

As a rough guide, expect around £80–£150 per m² supplied and laid by a professional, depending on the slab — concrete at the lower end, porcelain and premium natural stone at the top. DIY material costs (slabs, MOT Type 1, sand, cement, jointing) are often £40–£90 per m². Use the patio planner and full calculator to get accurate quantities for your own quotes.

How much waste should you allow when ordering patio slabs?

Add about 10% on top of your measured area for cutting waste, breakages and the odd faulty slab — more like 12–15% for circles, diagonal (45°) laying patterns, lots of curves or small awkward areas where you cut more slabs. For MOT Type 1 sub-base and bedding sand, allow roughly 10% extra too, as material compacts and is lost in handling. Always order natural stone and porcelain in one batch so colours and thicknesses match. The full calculator applies the right waste percentage automatically for your slab size and layout.

Can you lay a patio on sand?

You can lay some concrete slabs and block paving on a 30–50 mm screeded sharp-sand laying course, but the sand must sit on a compacted MOT Type 1 sub-base — never straight onto soil — and you must use sharp sand, not soft building sand. Sand bedding is not suitable for porcelain or most natural stone, which need a full wet mortar bed. For a patio that won't rock or settle, a mortar bed over a proper sub-base is the more reliable choice.

When should I use the full patio calculator instead of the quick planner?

The planner on this page gives a fast estimate of area, slab count and rough quantities — ideal for a first look. Use the full patio build-up calculator when you need exact figures to order or quote: it accounts for your specific slab size and thickness, cutting waste, bedding and full mortar-bed quantities, MOT Type 1 tonnage and bulk bags, spoil and muck-away, drainage falls and DPC clearance, and clay/soft-ground adjustments. If you're buying materials or pricing a job, run the full calculator and the patio fall calculator before you commit.

How to Lay a Patio — Step-by-Step UK Guide & Calculator

Difficulty

Intermediate DIY — methodical work, no specialist skills, but heavy and time-consuming.

Time

A small 10–20 m² patio: one to two weekends, plus curing time.

Cost

DIY materials ~£40–£90/m²; professionally laid ~£80–£150/m².

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.

Choosing your patio slabs

The slab you pick changes the bedding, the fall and the cutting. Porcelain and natural stone need a full wet mortar bed; concrete can sit on mortar or a screeded sharp-sand bed. Smooth slabs need a slightly steeper fall to shed water.

Porcelain

Durability: Excellent
Bedding: Full wet bed + slurry primer
Notes: Dense, frost- and stain-proof, low maintenance. Hardest to cut — needs a diamond blade.

Sandstone

Durability: Very good
Bedding: Full mortar bed
Notes: Natural, riven texture with good grip. Seal to resist algae; colours mellow over time.

Limestone

Durability: Good
Bedding: Full mortar bed
Notes: Smooth, contemporary look. Mid-range cost; seal against staining.

Concrete

Durability: Good
Bedding: Mortar or sharp-sand bed
Notes: Most affordable, huge choice of finishes. Heavier and can fade; seal to limit algae.

Slab	Durability	Bedding	Notes
Porcelain	Excellent	Full wet bed + slurry primer	Dense, frost- and stain-proof, low maintenance. Hardest to cut — needs a diamond blade.
Sandstone	Very good	Full mortar bed	Natural, riven texture with good grip. Seal to resist algae; colours mellow over time.
Limestone	Good	Full mortar bed	Smooth, contemporary look. Mid-range cost; seal against staining.
Concrete	Good	Mortar or sharp-sand bed	Most affordable, huge choice of finishes. Heavier and can fade; seal to limit algae.

Tools, materials & safety

Tools

Spade, shovel & wheelbarrow
Plate compactor (wacker plate)
Pegs, string line & tape measure
Spirit level & long straight-edge
Rubber mallet & bolster
Angle grinder / cut-off saw with diamond blade
Bucket, trowel & pointing tool
Cement mixer (for larger jobs)

Materials

Paving slabs (+ ~10% cutting waste)
MOT Type 1 sub-base
Geotextile membrane (clay / soft ground)
Sharp sand & cement, or ready-mixed bedding mortar
Slurry primer (porcelain & natural stone)
Jointing compound or kiln-dried sand
Edge restraint / haunching concrete where needed

Safety first

Slabs are heavy — lift with two people and bent knees. Before digging, use a CAT scanner to check for buried pipes and cables (services should be 450 mm+ deep). Wear gloves, goggles, a dust mask and ear defenders when cutting or compacting, and wash off wet cement, which burns skin.

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.

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.
Set string lines to your finished slab level, then set the fall into those lines so water runs away from the wall.
Square the area by measuring diagonals — equal diagonals mean square corners.
Dry-lay to check the layout falls on whole slabs and even joints before you dig.

Damp-proof course (DPC) clearance

Finished paving sits at least 150 mm — two brick courses — below the DPC and falls away from the wall.

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.

Drainage fall (side view)

A gentle, even slope so rainwater always runs away from the house, never toward it.

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

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.

A landscaper levelling compacted MOT Type 1 sub-base between timber pegs and string lines in an excavated patio area, with a plate compactor nearby — Spread and compact MOT Type 1 in 75–100 mm layers — never one deep dump — for a base that won't sink.

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.
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.
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.
Aim for 100 mm of compacted sub-base on good ground, 150 mm on clay — and keep the fall consistent through the base.

Interactive cross-section

Hover or tap a layer to explore depths, fines limits and the geotextile.

MOT Type 1 sub-base

100–150 mm

SHW Clause 803 · 0/31.5 mm · fines ≤9% (UF9)

The load-bearing layer. Graded crushed stone to dust that locks together under compaction. Use Type 3 (Clause 805, fines ≤5%) where SuDS requires drainage. Compact in 75–100 mm lifts.

Typical UK driveway build-up, top to bottom. Layer heights are indicative, not to scale.

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.

Hands tapping a large grey porcelain paving slab level onto a full wet mortar bed with a rubber mallet, trowel and bucket of mortar alongside — Bed each slab fully and tap it down to the string line — check the level and the fall as you go.

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

Bedding method — why a full bed wins

A continuous wet mortar bed supports the whole slab. Five dabs leave voids that crack slabs and trap water.

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.

A person brushing grey resin jointing compound into the joints of a newly laid grey porcelain patio with a soft broom — Work jointing compound fully into damp joints and tool it off — clean any residue before it cures.

Pointing & jointing — pick by joint width

The right jointing depends on how wide your gaps are. Tap an option to see the method.

Brush-in jointing compound

An all-weather resin/slurry compound brushed and tooled into damp joints from 3–50 mm. The easiest, most durable DIY option and the standard 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.

Patio variations & common questions

Laying a patio without cement

Some concrete and natural-stone slabs can be laid on a screeded sharp-sand bed over a compacted MOT Type 1 sub-base, then jointed with kiln-dried sand or a brush-in compound. It's faster and cheaper, but slabs are more likely to settle or rock and it isn't suitable for porcelain. For a patio that lasts, a full mortar bed is the safer route.

Laying a patio on grass

Never lay slabs straight onto grass — the turf rots and compresses and the patio sinks unevenly. Strip the turf, dig out the topsoil to firm subgrade, then build a proper compacted sub-base and bedding layer. The dig is the job; the slabs are the easy part.

Laying a patio on soil

Topsoil is soft and full of organic matter, so it must come out. Excavate to firm subgrade, add a geotextile if the soil is clay, then compact a 100–150 mm MOT Type 1 sub-base before bedding and laying.

Laying a patio on sand

A screeded sharp-sand laying course (30–50 mm) over a compacted sub-base works for some concrete slabs and block paving — but the sand must sit on MOT Type 1, never on soil, and it shouldn't be used for porcelain. Use sharp sand, never soft building sand.

Laying a patio on concrete

An existing concrete slab can be a base if it's sound, falls away from the house and drains. Lay porcelain or stone on a full bonded mortar bed (with primer); a thin bed adhesive can work for porcelain on a flat, clean slab. Check the finished level still clears the DPC by 150 mm.

Porcelain patios

Porcelain is dense, frost-proof and low-maintenance but unforgiving to lay: it must go on a full wet mortar bed with a slurry primer brushed onto the back of every slab, jointed with a brush-in compound, and cut with a diamond blade. It rewards careful setting out because mistakes are hard to disguise.

Raised patios

A raised patio needs a retaining structure (block or brick walls on a concrete footing), drainage behind the wall, and a hardcore-filled, compacted build-up — not just deep soil. They're a bigger structural job; if it retains significant height near a boundary or affects drainage, check whether you need building regulations or planning input.

Common mistakes & how to avoid them

Spot/dab (five-spot) bedding

Why it fails: Five blobs of mortar leave hollow voids that hold water and crack slabs under load.

How to avoid it: Always lay on a full, continuous bed so the whole slab is supported.

Skimping on the sub-base

Why it fails: A thin or poorly compacted base sinks and rocks within a season.

How to avoid it: Compact 100–150 mm of MOT Type 1 in 75–100 mm layers; add a geotextile on clay.

No fall, or falling toward the house

Why it fails: Flat patios puddle; a fall toward the wall pushes water at the building and over the DPC.

How to avoid it: Build in a 1:60–1:80 fall away from the house into your string lines and sub-base.

Bridging the damp-proof course

Why it fails: Paving above or within 150 mm of the DPC lets damp track into the masonry.

How to avoid it: Keep the finished level at least two brick courses below the DPC, with a channel drain if needed.

Slabs, sub-base & jointing — get prices

Partner links for the slabs, MOT Type 1, bedding, jointing and tools used in this guide — we may earn a small commission if you buy, at no cost to you.

Frequently asked questions

Patio build-up calculator Patio fall calculator Porcelain vs natural stone Sub-base specifications guide Block paving calculator All guides

Patio planner — instant build spec