How is this calculated?

Stone area is your patio area plus a waste allowance for the many irregular cuts. Riven stone is sold by area or by weight at roughly 10 m² per tonne (8-12 m²/t depending on piece size). Bedding mortar is a full bed at your chosen depth (default 50 mm) at a density of about 2,000 kg/m³, so a 50 mm bed works out to roughly 100 kg of dry mortar per m² (about 100 kg sharp sand + 20 kg cement in a 5:1 mix). Sub-base is MOT Type 1 at 100 mm compacted (~2.0 t/m³, ~200 kg/m²).

Should I add extra for wastage?

Yes — for crazy paving allow 10-15% rather than the 5-10% used for regular rectangular slabs. The irregular jigsaw layout means many pieces are trimmed to fit, so breakages and off-cuts are higher. This calculator defaults to 15% to suit intricate riven-stone work.

Where can I buy materials?

Riven Yorkstone and sandstone crazy paving comes from stone yards and landscaping suppliers (often sold by the tonne or in crates). Sharp (grit) sand, cement and MOT Type 1 sub-base are stocked by builders merchants and aggregate suppliers in 25 kg bags or loose/bulk-bag form.

What stone is best for crazy paving?

Natural stone like York stone, sandstone, or slate works best. Mix sizes and shapes for an authentic look. Reclaimed stone gives character but check for consistent thickness so it beds evenly.

Is crazy paving easier than regular paving?

In some ways yes, as you do not need precise cuts. However, fitting pieces together like a jigsaw and maintaining even joints requires patience and a good eye. Lay on a full 40-50 mm sharp-sand:cement bed over a 100 mm MOT Type 1 sub-base, and point the joints with a stiff 3:1 sharp-sand:cement mortar or slurry grout.

GardenCalcs

Crazy Paving Calculator

Estimate crazy paving quantities and mortar for irregular layouts.

Area

Patio/path area to be paved — measured flat, not allowing for slope

How We Calculate This

Crazy paving is laid on a full mortar bed of about 40-50 mm (not a spot/dab fix) over a compacted 100 mm MOT Type 1 sub-base for a patio (150 mm and a concrete base for vehicles). This calculator estimates the riven stone (per m² and per tonne at ~10 m²/t), the bedding mortar at ~2,000 kg/m³, and the sub-base at ~2.0 t/m³. Point the joints afterwards with a stiff 3:1 sharp-sand:cement mortar.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.