Basic Steps

Foundations must be firm and of a hardcore base (ideally washed crushed stone or medium grade concreting sand) of at least 100mm thick or 150mm for an unstable soil such as thick clay.

When laying a patio or path it is not necessary to prepare a sub-base, providing the underlying ground is firm. The area should be dug out to about 100mm (to allow for the blocks and the sand bedding layer.) This should then be compacted using a garden roller. A 50mm sand bedding layer should be prepared as for a driveway (although the sand can be compacted using a garden roller rather than a plate vibrator). The required digging depth must allow for the hardcore base.

The laying course material may be spread in one layer and screeded to the appropriate level, making due allowance for the reduction in thickness achieved during compaction.

Any hard surfaced areas such as drives or patios will be impervious and should incorporate a 1 in 40 fall or slope away from buildings to allow drainage of rainwater. To set this 'fall' use a spirit level on pegs 2 metres apart, placing a 50mm block of wood on the second peg beneath the straight edge.

Tap this peg down until you get a level reading. To avoid breaching or damaging the damp proof course of a house, a paved area must finish at least 150mm (6in) below this line. Also, where necessary drainage channels should be installed.

Bedding In

Firm edgings are essential to keep the blocks from sideways movement. Edgings set in concrete or a concrete haunching are ideal. All pavers are laid by hand with joint widths of approximately 2-5mm in a specified pattern. Full pavers should be laid first from an existing laying face or edge restraint and carried on to complete the days work area. Leave spaces around obstructions i.e. manhole covers and put cut blocks in later. Blocks should be cut using a mechanical or hydraulic block-splitter. Use a kneeling board and lay planks to carry barrows, to avoid shifting or tilting blocks which have been laid but not bedded in.

Compressing

When the surface is complete, the area should be compressed twice or three times by an appropiate vibrator, ensuring that vibration does not occur within 1metre of any unrestrained edge. In the case of patios or paths bedding can be completed by a club hammer or mallet using an off-cut of wood. This action will cause the sand from below to penetrate the block joints.

Finishing

Clean dry sand or crushed rock fines should be brushed over the surface and into the joints. The area should then be recompressed.This filling and final compaction helps make the surface impermeable and causes better ‘interlocking’ of the blocks. The area is then ready for trafficking. It may be necessary to top up the joints after initial trafficking.