Advanced options
Under the sand: 100-150mm of compacted MOT Type 1 sub-base (more for driveways than paths), edge restraints set in concrete before laying starts, and a whacker plate hired for both sub-base and final bedding-in. Herringbone at 45 or 90 degrees is the driveway pattern for a reason: it locks against braking forces that stretcher bond creeps under.
What The Block Paving Calculator Works Out
- Blocks: area x blocks per square metre plus 5% for cuts and breakages. The standard 200 x 100mm block tiles at exactly 50 to the square metre, so a 20m2 drive is 1,000 blocks before the allowance; large-format 240 x 160mm blocks run about 39/m2.
- Sharp sand laying course: area x 50mm depth x 1.6 tonnes per cubic metre, screeded off level rails. Blocks are laid from a corner working off the laid surface, never the bed.
- Kiln-dried joint sand: about 2kg per square metre brushed and vibrated into the joints after the final compaction, in 25kg bags. Re-sanding every couple of years is the whole weed regime: weeds root in windblown dust, not from below.
- Blocks per m2 and cuts allowance (advanced): type the coverage from the pack label and set your own wastage. Patios with few cuts manage 3%; a drive with curves and manholes wants 7% to 10%.
- Laying pattern (advanced): 45-degree herringbone adds about 5% more cuts than stretcher bond or 90-degree herringbone because every edge is a mitre. Herringbone earns its driveway monopoly structurally: the interlock resists braking and turning forces that stretcher bond creeps under.
- Laying course and sub-base depth (advanced): adjust the sand bed (50mm is standard) and choose 100mm of MOT Type 1 for a path, 150mm for a drive or 200mm on soft clay. The sub-base, at about 2.1 tonnes per cubic metre compacted, is the actual pavement; the blocks are merely its wearing surface.
- Edge restraint (advanced): enter the unsupported perimeter to get the number of 200mm edging blocks laid on end and the bags of concrete to haunch them. Edges go in before any block is laid: unrestrained edges are how patterns unravel.
- Excavation (advanced): the dig depth (sub-base plus sand plus a 50mm block) and the spoil volume, with a skip count allowing 25% bulking. Lay geotextile on clay or soft spots and compact the sub-base in two layers with a hired whacker plate.
- Materials cost (advanced): blocks at your price per square metre (standard concrete blocks are typically GBP 18 to GBP 30/m2, clay pavers GBP 45 and up) plus sand and MOT at a per-tonne delivered price. Edging, joint sand and plant hire are extra.
- Materials table (advanced): packs of blocks (about 9.6m2 per pack), bulk bags of sand and MOT, and the total delivered weight, which on a 20m2 drive is easily 10 tonnes. Front-garden paving falls under the permeable surfacing rules: ordinary blocks need drainage to a lawn or soakaway, permeable systems satisfy the rule outright.