Paving Calculator
Slabs, mortar bed, pointing, and sub-base quantities for any paved area.
Recommended for driveways (150 mm) and most garden paving (100 mm).
Full mortar bed: 40 mm typical. Best for natural stone and porcelain.
Used to calculate pointing volume in joints.
Paved Areas
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Frequently Asked Questions
How many paving slabs do I need per square metre?
Divide 1 m² by the area of one slab. A 600 x 300 mm slab covers 0.18 m² = 5.56 slabs/m² (round up to 6). Add 10% waste for edge cuts; 15% for diagonal layouts. Check pallet coverage in m² when buying - it varies by supplier.
What sub-base depth do I need for paving?
Pedestrian patio/path: 100 mm compacted MOT Type 1 + 30-50 mm sand or mortar bed. Driveway (occasional cars): 150 mm Type 1. Heavy traffic or block paving: 200 mm Type 1. On clay or frost-susceptible subgrades: increase depth or add a geotextile membrane to prevent mixing with subsoil.
What is the difference between mortar bed and sand bed paving?
Mortar bed (rigid): natural stone and large slabs on 5:1 sharp sand:cement bed, pointed with wet mortar joints. Sand bed (flexible): block paving on 30-50 mm compacted sharp sand, joints filled with kiln-dried sand - accommodates ground movement without cracking. Porcelain/large-format tiles: full-bed adhesive system on concrete base.
How many decking boards do I need?
Divide deck width by (board width + gap). A 125 mm board + 6 mm gap = 131 mm per run = 7.63 boards per metre of width. A 4 x 3 m deck: 7.63 x 4 = 31 boards (3 m lengths) + 10% waste = 35 boards. Allow separate quantities for joists (47 x 150 mm C16 at 400 mm centres) and fascia boards.
Do I need planning permission for a patio or decking?
Ground-level patios: generally no permission needed. Decking is permitted development if: no more than 300 mm above ground; covers no more than 50% of garden area; not on a listed building. Decking over 300 mm high may need permission. Conservation Areas and listed buildings: check with your Local Planning Authority.
Do I need a permeable surface for a front garden driveway?
In England, paving over 5 m² of a front garden with an impermeable surface requires planning permission. Use a permeable surface (permeable block paving, gravel, or gravel stabilisation grid) and no permission is needed for any area. Applies to front gardens only - rear garden patios are not subject to this rule.