Patio Paving Calculator
Calculate paving slabs needed for your patio or path. Includes jointing sand estimate.
By Konstantin Iakovlev · Founder, Calks.uk
Last updated: · Verified against HMRC and GOV.UK 2026/27 rates
Slabs Needed
34
Area
12.0 m²
Jointing Sand
60 kg
Slab Cost
£119.00
Disclaimer
This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.
How It Works
Paving calculations divide the total area by the area of a single slab or paver block. Common UK paving slab sizes include 450 × 450 mm (approx. 5 per m²), 600 × 600 mm (approx. 2.8 per m²) and 600 × 300 mm (approx. 5.6 per m²). Block paving (200 × 100 mm) requires approximately 50 blocks per m².
Allow a 10 mm joint between slabs (reduces coverage slightly) and add 5–10% extra for cuts and breakage. The calculator also estimates sub-base material: a 100–150 mm compacted Type 1 sub-base is standard for patios, while driveways need 150–200 mm. A 25–40 mm mortar or sand bed sits on top.
Enter the area dimensions, slab size and joint width. The calculator shows slabs needed, sand or mortar quantity, sub-base material in tonnes and estimated cost. For driveways over 5 m² of impermeable paving, planning permission may be required unless you use permeable paving or drain to a lawn or border.
How many paving slabs do you need? Number = area ÷ slab area. Add 5-10% for cuts. Sample 20 m² patio with 600×600mm slabs (0.36 m²): 20 ÷ 0.36 = 56 slabs + 10% = 62 slabs. Standard UK slab sizes: 450×450, 600×600, 600×900, 600×300mm (most popular), random/multi-pack natural stone. Patterns affect waste: straight bond 5%; running bond 7%; herringbone 10-15%; random natural stone 10-15%.
UK paving types and prices 2026. Concrete slabs (basic): £8-£20/m². Concrete riven/textured: £20-£40/m². Block paving (clay/concrete bricks): £20-£50/m² + sand bedding. Natural sandstone (Indian, York stone): £30-£80/m². Limestone: £40-£90/m². Slate flag: £50-£120/m². Granite setts/cobbles: £40-£150/m². Porcelain outdoor 20mm: £40-£100/m² — premium, no fading, no sealing. Fitting labour £40-£80/m² depending on complexity and pattern. Total typical UK patio cost: £80-£180/m² installed.
Sub-base — the foundation for permanent paving. Strip topsoil 200-300mm. Lay weed membrane. 150mm compacted MOT Type 1 sub-base (£40-£60/tonne, ~2 tonnes per 10 m² at 150mm). Compact with wacker plate (£50/day hire). 25-40mm sharp sand or mortar bed for slabs. Block paving uses 50mm sand bed with jointing sand swept in after laying. Falls: 1:60 slope away from house for drainage (1.67% gradient). Drainage channels (Aco Drain) at building edges and large patios.
Planning permission for paving. Front gardens (England, since 2008): permeable surfaces (gravel, permeable block paving, porous concrete) qualify for permitted development. Impermeable surfaces (sealed concrete, traditional block paving on impermeable sub-base) require planning permission. Back gardens: generally no permission needed for under 50% coverage of curtilage. Listed buildings: any external work to curtilage may need listed building consent. Conservation areas: tighter rules — check council. Article 4 directions remove permitted development rights in some areas.
Maintenance and longevity. Concrete paving: 25-50 year life; weeds in joints common (treat annually or use polymeric jointing sand). Sandstone: 40-70 years; algae growth in damp shaded areas (pressure wash 1-2 yearly). Porcelain: 50+ years, stain-resistant, no sealing required. Block paving: 25-40 years; relevelling every 5-10 years where ground settles. Cleaning: pressure washer (£100-£300) annually. Sealants: only on porous stone, repeat every 2-5 years (£20-£40/litre, covers 4-8 m²). Joint cleaning: replace polymeric jointing sand every 7-15 years.
Example: Patio 4 m × 3 m, 600 × 600 mm slabs, 10 mm joints
- Area: 12 m²
- Slabs per m² (with joints): 2.7
- Total slabs: 12 × 2.7 = 32.4, round up to 33 + 5% = 35 slabs
- Sub-base (Type 1, 100 mm depth): 12 × 0.1 × 2.1 t/m³ ≈ 2.5 tonnes
- Mortar bed (30 mm): ~10 bags of sand-cement mix
Frequently Asked Questions
- Do I need planning permission for a patio or driveway?
- Front gardens (since 2008): permeable surfaces (gravel, permeable block paving, porous concrete) qualify for permitted development. Impermeable surfaces (sealed concrete, traditional block paving on impermeable base) over 5 m² require planning permission. Back garden patios: generally no permission needed under 50% coverage. Listed buildings: any external work needs listed building consent. Conservation areas: tighter rules. Article 4 directions remove permitted development rights in some streets — check council before laying.
- How long does a patio installation take?
- DIY 20 m² patio: 3-5 days for two people including base preparation. Professional installation: 2-3 days for 20 m². Sequence: day 1 — excavation, lay weed membrane, MOT Type 1 sub-base (compact in 50mm layers). Day 2 — install edging, lay slabs on mortar bed, level. Day 3 — point joints, finish edges, clean. Allow 48 hours curing before walking, 7 days before furniture. Block paving slightly faster than slabs (no pointing needed, just sand sweep).
- What's the best paving for a UK garden?
- Concrete slabs: cheapest (£8-£20/m²), reliable, basic appearance. Indian sandstone: popular mid-range (£30-£60/m²), warm colours, riven texture. Limestone: more uniform than sandstone, modern look (£40-£80/m²). Porcelain: premium choice (£40-£100/m²), no fading, no sealing, frost-proof, but harder to cut. Block paving: vehicle-rated, replaceable individual units (£20-£50/m²). Slate: distinctive, expensive (£50-£120/m²), slippery when wet. Natural stone needs sealing every 2-5 years; porcelain and concrete don't.
- Why is my patio uneven or moving?
- Common causes: inadequate sub-base (less than 150mm MOT Type 1 compacted); poor compaction; insufficient mortar bed (should be 25-40mm on full bed, not 'spot' bedded on 4 corners); ground heave (clay soils expand when wet); tree roots; frost heave (water gets under slabs, freezes, lifts). Fix: lift affected slabs, redo sub-base properly. Spot-fixing rarely works long-term. Block paving issues: edging course not concreted in — bricks migrate sideways without restraint. Always concrete edge courses on driveways.