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Paving & Decking Calculator

Calculate slabs, mortar, sub-base, and pointing for paving projects - or boards, joists, noggins, and fixings for timber and composite decking.

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

Name Length (m) Width (m)

Job Costing (optional)

Results

Common Slab Sizes

Sizeper m²
600 × 600 mm2.78
600 × 300 mm5.56
450 × 450 mm4.94
900 × 600 mm1.85
600 × 450 mm3.70
Block 200 × 100 mm50
Sett 100 × 100 mm100

Paving Build-up

  • Driveway: 150 mm MOT Type 1 + 40 mm mortar bed + slab
  • Patio (good ground): 100 mm MOT + 40 mm mortar bed + slab
  • Patio (stable ground): 50 mm sharp sand + slab (pedestrian only)
  • Block paving: 100-150 mm MOT + 50 mm sharp sand + block + kiln-dried sand brush-in
  • Setts: 100 mm MOT + 40 mm mortar bed + sett + mortar pointing

Decking Tips

  • Allow 5-6 mm gaps between softwood boards for drainage and expansion
  • Use stainless steel or hot-dip galvanised fixings only - standard steel rusts
  • Treat all cut ends with end-grain preservative before fitting
  • Joists should slope ≥1:100 away from the house for water runoff
  • Check if planning permission is needed - decks over 300 mm height or 50% garden coverage may require it
  • Composite decking: always follow manufacturer's fixing gap and clip system

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