NZ Landscaper Magazine
PAVING UNITS - PART 2 CONT.
EXCAVATION AND HARDFILL
The key to good paver performance is the preparation of the base to provide a sound, even footing for the pavers to be laid over. Inadequate preparation may end in expensive remedial work.
Excavation of the paved area must include removal of topsoil and all organic matter. The depth to be excavated will depend on paver thickness, hardfill and sand depths and the intended use of the paving.
The bearing capacity of the soil under the paving can be indicated by a heel test carried out after the initial excavation has begun:
Areas of soft ground must be removed down to solid bearing and the resulting excavation filled with compacted hardfill. If not remedied, areas of soft ground will show in the completed paving as a hollow or settlement.
When placing hardfill:
Weak – walking leaves a very noticeable sunken footprint. Medium – a footprint is left with a small amount of soil compression.
Strong – no impression is left in the soil.
Remove excavated material clear of the work area.
Form falls in the excavated base. Finish the surface to +0 or -20mm.
Compact the material in 100mm (maximum) layers – for small works, use a plate compactor or a hand-pulled roller.
Finish the surface to +0 or -10mm.
All paving requires some form of edge restraint to hold the pavers in place. Options are:
Square or rectangular pavers set into a concrete haunch. Concealed flexible PVC paving edge for paving 40-80mm thick. Kerbing – precast concrete, stone blocks or cast in situ concrete. H4-treated timber (or durable hardwoods) securely pegged. Stone blocks.
Stone blocks, precast kerbing, pavers and other unitary edge units all require setting into a concrete haunch to accurately locate and hold them in place.
BEDDING MATERIAL (SAND/CRUSHER FINES)
Sand or crusher fines are the beddings that the pavers are laid directly onto. The bedding supports the pavers but will not mask irregularities in the hardfill if it does not meet the required tolerances.
The bed should be 20-30mm thick when compacted (allow 5-10mm for compaction) and damp but not wet.
When laying, allow additional thickness for compaction and screeding to level. Limit the area of prepared bedding to a size that will be paved over in a single work session. Jointing sand or joint-filling sand is specially produced to lock pavers into place. Some proprietary products are suitable for paving on sloping ground, areas of high wind or areas that are regularly swept (including by mechanical sweepers). Even after curing, these products typically still allow slight movement of the pavers. Some have additives that inhibit weed growth or insect infestation. If choosing a branded product, ensure it does not produce leachates.
• hammer and a short thick piece of timber.
Cut pavers to fit as work proceeds. Recommended cutting methods are a concrete saw or paving splitter as they give more accurate cutting, but for small jobs, a bolster chisel may be used.
After laying, sweep dry sand into all joints then revibrate the area, repeating the process until all joints are filled.
Keep vehicles off the paved area until all work is complete. Use a running board when transporting materials across the unfinished paving in a wheelbarrow.