How to Lay a Patio: Step-by-Step Guide for DIYers

Laying a patio is one of those projects that looks intimidating but is well within the reach of a competent DIYer. It’s physically hard work — there’s no getting around the digging — but the skills involved are straightforward. Get the foundation right, take your time with the levels, and the slabs practically lay themselves.

This step-by-step guide covers the entire process from planning to pointing, with the specific measurements, material quantities, and techniques that make the difference between a patio that stays flat for decades and one that sinks within a year.

Planning Your Patio

Size and Position

Before you buy a single slab, spend time planning. The most common mistake is building a patio that’s too small — it looks and feels cramped once you add furniture.

Minimum useful sizes:

• Small bistro table and two chairs: 2.5 × 2.5 metres minimum
• Four-seater dining table: 3 × 3 metres minimum
• Six-seater table with room to move: 4 × 3.5 metres
• Dining plus lounging area: 5 × 4 metres or more

Position: South or west-facing is ideal for catching afternoon and evening sun. Consider proximity to the house (you want the kitchen door close for carrying food out), how it connects to the garden, and whether you’ll need to cross grass to reach it (a stepping stone path saves the lawn).

Regulations: In most cases, you don’t need planning permission for a patio in the UK. However, if it’s raised above the existing ground level by more than 300mm, covers more than half the garden area, or is in a listed building curtilage, check with your local planning department first.

Choosing Your Paving Material

The material you choose affects the look, cost, and to some extent the laying process:

For a first patio project, I’d suggest standard concrete slabs (600 × 600mm) or Indian sandstone. Concrete slabs are uniform in size and thickness, making them the easiest to lay. Indian sandstone looks significantly better but varies in thickness by up to 10mm slab to slab, so you’ll need to adjust the mortar bed more.

Calculating Materials

Here’s what you’ll need for a typical 3 × 4 metre patio:

Tip: Order 10% more slabs than your exact calculation. Cuts generate waste, and you’ll inevitably crack one or two. Having spares saves a trip back to the merchant mid-project.

Tools and Materials You’ll Need

A complete list so you’re not caught short on day one:

• Spade and shovel — for excavation
• Wheelbarrow — you’ll shift a lot of material
• Spirit level (at least 1200mm) — for checking levels across slabs
• Laser level or line level — for setting the fall across the full patio
• String line and pegs — for marking out and setting levels
• Rubber mallet — for tapping slabs into position
• Plate compactor (hire) — for compacting the sub-base. You can get by with a hand tamper for small patios, but a compactor does a far better job.
• Mixing bucket or spot board — for mortar
• Pointing trowel — for filling joints
• Tape measure (at least 5m)
• Knee pads — you’ll be on your knees for hours. Seriously, don’t skip these.
• Angle grinder with diamond blade (or hire a slab cutter) — for cutting slabs to fit edges and corners

Step 1 — Mark Out and Excavate

Mark the patio outline using string lines stretched between wooden pegs. Make sure the corners are square — measure diagonally from corner to corner. If both diagonals are equal, your rectangle is square. If they’re not, adjust until they match.

Excavation depth: You need to dig down far enough to accommodate:

• 150mm of compacted sub-base
• 30-40mm of mortar bed
• The thickness of your slabs (typically 20-35mm for concrete, 22-30mm for natural stone)

Total depth: roughly 200-225mm below the finished patio surface level. The finished patio should sit at least 150mm (two courses of brick) below the damp-proof course of the house to prevent moisture bridging.

Dig out the area, removing all topsoil and any soft or organic material. The base of the excavation should be reasonably level and on firm, undisturbed ground. If you hit soft spots or old tree roots, dig them out and backfill with sub-base material.

What to do with the soil: A 12m² patio generates roughly 2.5-3 cubic metres of soil. That’s a lot. Plan where it’s going before you start digging — raised beds, levelling other parts of the garden, or a skip.

Step 2 — Create a Compacted Sub-Base

The sub-base is the foundation of your patio. Get this wrong and the slabs will sink and shift, no matter how well you lay them.

1. Add MOT Type 1 sub-base material in layers. Tip it in and spread it roughly level with a rake.
2. Compact in layers of 50-75mm. Don’t dump the full 150mm in and compact once — it won’t compact properly at depth. Add 50-75mm, compact with a plate compactor (or hand tamper), then add the next layer and compact again.
3. Check the level as you go. The top of the sub-base should be roughly parallel to your intended finished surface, including the drainage fall (more on that below).

A properly compacted sub-base should feel solid underfoot — like standing on a road surface, not soft ground. If it gives when you stand on it, compact more.

Step 3 — Mix and Lay the Mortar Bed

Each slab sits on a bed of mortar. The standard mix is:

5 parts sharp sand to 1 part cement (by volume). Mix it dry first until the colour is uniform, then add water gradually until you get a stiff, damp consistency — like a crumbly cake mix. It should hold its shape when squeezed but not be wet or sloppy.

For each slab, trowel a full bed of mortar onto the sub-base, roughly 30-40mm deep and slightly larger than the slab. Some people use the “five-blob” method (a blob at each corner and one in the centre), but a full mortar bed is significantly stronger and prevents slabs rocking.

Why a full bed matters: The five-blob method leaves voids under the slab. Over time, the slab flexes over the voids and cracks, especially under heavy loads (like a car tyre if you’re paving near a drive). A full bed supports the slab completely.

Step 4 — Lay the Slabs

Start from a corner — ideally the corner closest to the house. Lay the first slab carefully, as every other slab references this one.

1. Lower the slab onto the mortar bed gently. Don’t slide it — this pushes mortar up into the joint space.
2. Tap it down with a rubber mallet. Work around the edges and the centre, tapping firmly but not savagely. You’re aiming to bed the slab into the mortar until it reaches the target level.
3. Check the level. Place your spirit level across the slab in both directions. Adjust by tapping down the high side. Check the fall across the patio (see below).
4. Use spacers for consistent joints. 10mm spacers (or 10mm lengths of timber) give a consistent gap between slabs. For natural stone, 10-15mm joints look best. For concrete slabs, 8-10mm works well.
5. Work outward from your starting corner, laying one row at a time. Check the level across each new slab and between adjacent slabs.

Getting the Fall Right for Drainage

This is critical. A patio must slope slightly away from the house so rainwater drains off rather than pooling against the wall. The standard fall is:

1 in 60 — meaning a 1cm drop for every 60cm of patio width.

For a 3-metre-deep patio, that’s a 5cm fall from the house end to the garden end. Set this up with your string lines before you start laying: the string at the far end should be 5cm lower than at the house end.

Use a laser level to set the string lines accurately, or a long spirit level with a shim under one end to verify the fall as you work. Check constantly — it’s much easier to correct the fall as you go than to lift and re-lay slabs.

Consistent Spacing

Spacers are your friend. Consistent joints make or break the professional appearance of a patio. If your joints wander from 8mm to 15mm across the patio, it’ll look amateur no matter how flat and level the slabs are.

For natural stone with varying slab sizes, a dry layout (arranging slabs without mortar) helps you plan the pattern and ensure you don’t end up with awkward thin cuts at the edges.

Step 5 — Pointing the Joints

Leave the mortar bed to set for at least 24-48 hours before pointing. Walking on freshly laid slabs can shift them.

Pointing options:

• Dry mortar mix: Mix 3 parts sand to 1 part cement (dry). Brush it into the joints, compact it down with a pointing tool or thin piece of wood, and mist gently with water. Repeat until the joints are full. This is the traditional method and works well for wide joints.
• Wet mortar pointing: Mix the same ratio but with water to a stiff, workable consistency. Press it into the joints with a pointing trowel and smooth the surface. Cleaner finish but more time-consuming.
• Resin-based jointing compound: Brush-in compounds like GeoFix or similar are easier to apply — brush the dry compound into the joints and it sets with moisture. They’re more flexible than mortar (less prone to cracking) but significantly more expensive.

Whichever method you use: Clean any mortar or compound off the slab faces immediately. Once it sets on the surface, it’s extremely difficult to remove without staining. Keep a damp sponge handy and wipe as you go.

Mistakes That Lead to Sinking Slabs

Nearly every patio failure comes down to one of these:

1. Insufficient sub-base. Skipping the sub-base or laying less than 100mm (150mm is better) is the number one cause of sinking. The sub-base distributes the load and provides a stable foundation. Without it, the slabs are sitting on soil that shifts with moisture, frost, and settling.
2. Poor compaction. Even with the right depth of sub-base, if it’s not compacted properly it will settle over time. Hire a plate compactor — it’s £30-40 for a day and worth every penny.
3. Blob method on soft ground. The five-blob mortar method is fine on a solid concrete base. On a sub-base over soil, use full mortar beds.
4. No drainage fall. Water pooling on or under the patio erodes the sub-base and mortar over time. Even a slight fall (1 in 80 at minimum) prevents this.
5. Laying on topsoil. All topsoil and organic matter must be removed. Organic material decomposes, creating voids. Subsoil is stable; topsoil isn’t.

If you get the sub-base and compaction right, the rest is largely aesthetic. A patio on a solid foundation will last 20+ years with minimal maintenance.

Recommended Patio Laying Tools and Materials

Here’s a summary of what you need, with recommendations:

For the foundation:

• MOT Type 1 sub-base — order from a local builders’ merchant by the tonne. Delivery is usually £30-50 on top of the material cost.
• Plate compactor — hire for a day from a local plant hire company.

For laying:

• Sharp sand and cement for the mortar bed.
• A rubber mallet — get a decent one. The cheap ones split after a day of slab tapping.
• A 1200mm spirit level — longer is better for checking across multiple slabs.
• A laser level — invaluable for setting consistent fall across the full patio width. Even a basic cross-line level on a tripod does the job.

For cutting:

• A 230mm angle grinder with a diamond blade handles most slab-cutting needs. For lots of cuts, hire a petrol slab cutter — it’s faster and easier on the arms.

For pointing:

• Resin-based jointing compound (GeoFix or similar) for a clean, long-lasting finish.
• A pointing trowel for traditional mortar pointing.

For maintenance:

• A pressure washer for annual cleaning — your patio will grow moss and algae, especially in shaded areas. A quick wash each spring keeps it looking fresh.

Laying a patio is a weekend project (a long weekend, realistically) that adds genuine value to your house and gives you outdoor living space for years. The physical work is real, but the technique is learnable, and the satisfaction of sitting on a patio you built yourself — with a cold drink in hand — is hard to beat.