Paving Slab Calculator
Calculate paving slab quantities, mortar, sand, and sub-base materials for any patio or path. Works for any slab size and includes a 10% cutting waste allowance.
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Paving Installation Guide
What should I know about Sub-Base Requirements?
A solid, well-draining sub-base is the foundation of any long-lasting paved area. Pedestrian patio: 75-100mm compacted Type 1 hardcore (crushed concrete or MOT stone). Driveway: 100-150mm compacted Type 1 hardcore. Without adequate sub-base, slabs will rock, crack, and sink within a few years. The sub-base must be compacted with a plate compactor (hire from a tool hire shop, approximately £60/day) — using a hand rammer is insufficient for larger areas. For clay or soft soils: increase the sub-base depth beyond the standard recommendation, since these ground types are more prone to movement and settling over time.
What should I know about Laying Methods?
Dry mortar method (patio): lay slabs on 5 spots of firm mortar (one in each corner and one in centre), tap level with a rubber mallet, grout with dry sand or kiln-dried sand pressed into joints. Wet bed method (professional): spread a full mortar bed (4:1 sharp sand:cement, semi-dry), set slabs in one operation. This is better for large format slabs and driveway use. For driveways: use a full wet bed, and ensure the mortar strength is appropriate for vehicle loading. Indian sandstone and natural stone generally need a full wet mortar bed rather than a dry-laid approach, given their weight and the need for a stable, even base.
What do I need to know about Drainage Requirements?
From November 2008, replacing or extending front garden paving with impermeable materials requires planning permission in England unless a drainage system is incorporated. The permitted development right requires either using permeable paving (block paving with open joints, gravel, resin-bound) or directing water runoff onto a lawn or planted area. For rear gardens, there is no equivalent restriction. Newly paved areas should have a minimum fall of 1:80 (approximately 12mm per metre) away from the house, to prevent water pooling against the walls or finding its way toward the damp-proof course.
What's the key thing to understand about Jointing and Sealing?
Joint width: typically 10-15mm for standard paving, 3-5mm for precision-cut porcelain. Narrow joints require more accurate cutting. Jointing materials: kiln-dried sand (brush in, compact, repeat until full — budget option). Polymeric sand (activates with water to form a semi-rigid joint — resists weeds and ants effectively, £15-25 per 15kg bag). Mortar pointing (durable but cracks if sub-base settles — can look untidy if not done carefully). Sealing: porcelain requires no sealing. Sandstone benefits from sealing to reduce staining and make cleaning easier, though this needs periodic reapplication every few years.