How do I lay block paving?

Block paving is a flexible pavement. It works because every block is locked against its neighbours and the whole field is held by an edge restraint. Take away the restraint or under-do the sub-base and it spreads, ruts and sinks — which is what has happened to every failed drive you have seen.

Safety

What you'll need

• Blocks, plus 5-10% for cuts and breakages
• MOT Type 1 sub-base material
• Sharp sand for the laying course
• Kiln-dried jointing sand
• Edging kerbs and concrete for haunching
• A plate compactor with a rubber mat
• A block splitter or a disc cutter with water suppression

Step by step

1. Set the finished levels before digging.The paving must finish at least 150mm below any damp-proof course, and fall away from the house at around 1:60 to 1:80. Set string lines at the finished block level and work down from there.
2. Excavate to the full depth.Finished level, minus block thickness, minus 30-40mm laying course, minus the sub-base depth. That is typically 200-250mm total for a path and 300mm or more for a drive. Remove all soft material — the sub-base must sit on firm ground.
3. Lay and compact the sub-base in layers.MOT Type 1 in 75-100mm layers, each one compacted with a plate before the next goes down. Compacting 200mm in one go leaves the bottom half loose, which is the single most common cause of a sunken drive.
4. Set the edge restraints first.Kerbs or edging blocks bedded on concrete and haunched on the outside, set to the finished level and the fall. Everything else is laid up to these. Without a restrained edge the whole field creeps.
5. Screed the laying course to a consistent depth.Sharp sand, screeded to 30-40mm loose depth using screed rails and a straightedge. It must not be compacted before laying — the blocks are vibrated into it later.
6. Lay the blocks from a straight edge, never walking on the sand.Work forward off the laid blocks. Butt each block up to its neighbours with a 2-3mm nominal joint. A herringbone pattern interlocks best for a drive; stretcher bond is fine for a path.
7. Cut the edges last.Lay all the full blocks first, then measure, mark and cut the perimeter pieces. Cuts smaller than about a third of a block are unstable — adjust the layout instead.
8. Vibrate the blocks down.Two or three passes with a plate compactor and a rubber protection mat, working across the whole area. This beds the blocks into the sand and locks them together.
9. Joint with kiln-dried sand and compact again.Brush kiln-dried sand into every joint, vibrate again, top up and repeat until the joints stay full. The sand in the joints is what makes the pavement work — an unjointed block field has no interlock at all.
10. Top up the joints after a few weeks.Sand settles and washes out in the first rain. Brush more in once or twice in the first month.

Tips

• Take blocks from three or four packs at once and mix them. Colour varies between packs and laying pack by pack produces visible bands.
• A block splitter is quieter, dust-free and quicker than a disc cutter for straight cuts. Hire one rather than buying a cutting disc.
• Sweep the sand off the surface before the final compaction pass, or the plate grinds it into the block faces.

Common mistakes

• Skipping or under-compacting the edge restraint — Block paving is only stable because it is confined. An unrestrained edge lets the blocks spread sideways, the joints open, and the whole area ruts within a season.
• Compacting the sand laying course before laying blocks — The blocks are meant to be vibrated into a loose screeded bed. Pre-compacting it means they never settle evenly and the surface stays uneven.

If it doesn't work

Questions people ask