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Slab 50x50 calculator

50 × 50 cm slabs cover a surface fast: you need 4 slabs per m² without joints, or 80 slabs for a 20 m² patio. That makes them popular for patios and terraces with a clean, modern look.

Laying patterns for square slabs

Square slabs can go in stack bond, running bond or on the diagonal. Stack bond gives continuous joints in both directions, so it needs accurate work: any error shows along the whole line. Running bond breaks up the grid and hides small deviations. The diagonal looks lively but cuts every edge slab at an angle.

Load class

This page opens with the Drivable class, which uses a 30 cm base. For a patio, switch to Pedestrian and the base drops to 20 cm. Large slabs crack more easily under car wheels than small pavers, so driveways usually get smaller, thicker pavers.

Avoiding costly cuts

Every cut slab is expensive, and a small offcut is often waste. Plan the patio size around full slabs: with a 3 mm joint, each slab takes up 50.3 cm. The optimizer tests area changes within 5% and different joint widths and shows how many cuts each option needs.

FAQ

How many 50 × 50 slabs do I need for 20 m²?

80 slabs without joints or waste. Add a waste allowance in the planner, and the shopping list includes it.

Can I use 40 × 40 or 60 × 60 slabs?

Yes. The planner has a 40 × 40 cm exposed aggregate slab preset, and Custom dimensions takes any other size.

Key figures for this scenario

The figures come from the same formulas the planner uses. They leave out joints and waste; the planner's shopping list adds both for your surface shape.

Paver format
Large square slab (500x500 mm)
Laying pattern
Stack bond
Pavers per m²
4
Load class
Drivable
Base layer
30 cm crushed stone 0/32 mm
Bedding layer
4 cm grit 2/5 mm
Excavation depth
40 cm

Example: a 20 m² surface

For 20 m² you need about 80 pavers, 7.2 m³ of crushed stone (about 12.24 t, including a 20% compaction reserve) and 0.8 m³ of grit (about 1.2 t). Dig about 40 cm deep: 30 cm of base, 4 cm of bedding and 6 cm of paver.

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