How many paving slabs do I need per square metre?

The number of slabs per square metre depends on the slab size. For 450x450mm slabs with 10mm joints, you need approximately 4.7 slabs per m². For 600x600mm slabs, you need about 2.7 per m². For 300x300mm slabs, approximately 10.4 per m². Always add 5-10% for cutting waste.

How much sub-base do I need under paving?

For a standard patio, you need 100-150mm (10-15cm) of compacted MOT Type 1 sub-base. This equates to approximately 0.15-0.22 tonnes per square metre, as MOT Type 1 has a compacted density of about 1.5 tonnes per cubic metre. For driveways, increase to 150-200mm.

What sand should I use for paving?

Use sharp sand (also called grit sand or concreting sand) mixed with cement for the bedding layer under slabs. The standard mix is 5 parts sharp sand to 1 part cement. For jointing, use kiln-dried sand or a proprietary jointing compound like UltraScape. Do not use building sand (soft sand) for bedding as it retains water.

Do I need planning permission for a patio in the UK?

Most patios do not need planning permission if they are at ground level (within 300mm of the ground). However, if the patio covers more than 5 square metres and is not made of permeable paving or does not drain to a permeable area, you may need to comply with planning rules to manage surface water runoff. Always check with your local council.

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Complete Guide to Paving a Patio in the UK

Laying a patio is one of the most popular outdoor DIY projects in the UK, and getting the materials right is essential for a professional, long-lasting result. Whether you are creating a simple garden path or a large entertaining area, accurate material calculation saves money and prevents frustrating delays.

Types of Paving Slabs Available in the UK

The UK market offers a wide range of paving materials, each with different characteristics, prices and suitability:

Slab Type	Typical Price per m²	Best For
Concrete slabs (pressed)	£15-£30	Budget patios, utility areas
Concrete slabs (wet-cast)	£25-£50	Natural stone look on a budget
Natural sandstone	£30-£60	Premium patios, traditional gardens
Natural limestone	£35-£70	Contemporary, clean designs
Indian stone	£20-£45	Popular mid-range, natural look
Porcelain paving	£40-£80	Modern, low maintenance
Granite setts	£45-£90	Driveways, edging, traditional
Block paving	£20-£40	Driveways, paths

Sub-Base: The Foundation of a Good Patio

The sub-base is arguably the most important layer in any paving project. Without a properly compacted sub-base, your patio will inevitably sink, crack and become uneven over time. In the UK, MOT Type 1 (also known as crusher run or 804) is the standard sub-base material. It consists of crushed limestone or granite graded from 40mm down to dust, which compacts firmly to create a solid, stable base.

Sub-base depths for different applications:

Garden path (pedestrian only): 75-100mm compacted
Standard patio: 100-150mm compacted
Heavy-use patio or parking area: 150-200mm compacted
Domestic driveway: 200-300mm compacted

Key point: MOT Type 1 compacts to roughly 80% of its loose volume. If you need 150mm compacted depth, you should lay approximately 190mm of loose material before compacting with a whacker plate (vibrating plate compactor). Allow for this when calculating quantities.

Laying Patterns for Paving Slabs

The laying pattern you choose affects both the appearance and the number of slabs needed. Common patterns in UK gardens include:

Stretcher bond (brick pattern): Slabs are offset by half their length on alternating rows. This is the strongest pattern for resisting lateral movement and works well with rectangular slabs.

Stack bond (grid pattern): All joints align in a grid. Simple and modern-looking but structurally the weakest pattern. Best for patios with a solid border or edge restraint.

Random (multi-size): Uses several slab sizes laid in a planned random pattern. Creates a natural stone appearance. Requires careful planning to avoid creating obvious lines or repeating sections. Most natural stone paving packs from UK suppliers come in multi-size packs designed for this pattern.

Herringbone: Primarily used for block paving on driveways. The interlocking pattern provides excellent resistance to vehicle tyre forces. Requires more cutting at edges, increasing waste by 5-10%.

Bedding and Jointing

The bedding layer sits between the sub-base and the slabs, typically 25-40mm thick. The standard mix for patio slab bedding in the UK is:

Full mortar bed: 5 parts sharp sand to 1 part cement (5:1), mixed to a semi-dry consistency
Spot bedding: Five blobs of mortar per slab (four corners and centre) — faster but can lead to rocking and cracking
Porcelain paving: Requires a priming slurry and flexible adhesive (do NOT use sand/cement mortar as porcelain does not absorb moisture)

For jointing (filling the gaps between slabs), options include:

Kiln-dried sand: Brushed into joints. Cheap but washes out over time and allows weed growth
Dry jointing mix: 3 parts sand to 1 part cement, brushed in dry and misted with water. Cost-effective and reasonably durable
Resin jointing compound: Products like UltraScape or Geo-Fix set hard, prevent weeds and resist washing out. More expensive but excellent long-term results

Drainage Considerations for UK Weather

The UK's wet climate makes proper drainage essential for any paved area. Since 2008, Permitted Development rights require that any new impermeable paved area over 5m² must either drain to a permeable surface within your property boundary or use permeable paving. This means:

Sloping your patio away from the house at a gradient of 1:80 (approximately 12mm per metre) to direct water onto a lawn or flower bed
Installing a linear drain (channel drain) along the house wall if the patio is against the building
Using permeable jointing compounds that allow water through
Considering permeable block paving for driveways

Building Regulations note: Paving laid adjacent to a building must maintain a minimum 150mm gap below the damp-proof course (DPC). This is typically two brick courses below the DPC line. Failure to maintain this gap can cause damp problems.

How to Order Materials

For best value on paving materials in the UK:

Slabs: Buy from Wickes, B&Q, Jewson or a local builders' merchant. Delivery is usually free above a certain order value (typically £100-£300)
MOT Type 1: Order in bulk bags (approx 0.85t per bag) from a builders' merchant or aggregates supplier. Loose loads are cheaper for large projects
Sharp sand: Available in 25kg bags from all DIY stores or bulk bags from builders' merchants. A bulk bag (approximately 0.85t) covers about 5m² at 40mm depth
Cement: Standard 25kg bags of Portland cement from B&Q, Wickes or Screwfix. Rugby, Blue Circle and Hanson are the main UK brands

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