Edge restraints
Edge restraints hold ICPs firmly in place and resist the forces of traffic or minor settlement. They also serve an important function in holding bedding sand in place and preventing its migration.
Edge restraints are vital components and are essential for trouble-free performance. When a compacted aggregate base supports the pavers and bedding sand, the base should extend beyond the restraint. As a rule of thumb, the base should extend beyond the restraint the same distance as the thickness of the base material. For instance, if the base is 150-mm (6-in.) thick then it should extend at least 150 mm (6 in.) beyond the outside edge of the restraints. This adds stability to the restraint, especially in soils subject to heaving.
There are two general types of edge restraints. The first type includes products manufactured from plastic, precast concrete, cut stone, aluminum, steel, and timber. The second type is formed on-site and comprises poured-in-place concrete.
Manufactured edge restraints
Plastic edging will not rust or rot and provides a rigid structure when spiked in place (using steel spikes), as well as contributing flexibility when the pavement is subject to freeze-thaw, moisture, and loading. Plastic restraint systems can be cut quickly with a hacksaw and can be used with light-duty residential, commercial, or, depending on the design, in some heavy-duty industrial applications.
Aluminum and steel edging provides a smooth vertical surface against the pavers. Steel should be painted or galvanized so rust does not stain the pavers. Spikes to secure steel and aluminum edging should extend well into the base course. Consult manufacturer’s literature for the recommended spacing of the spikes. Aluminum and steel edging are manufactured in different thicknesses. The thickest edging is recommended when pavers are subjected to vehicular traffic.
Full-depth precast concrete or cut-stone edging can be set in compacted aggregate or concrete backfill. For pavements exposed to vehicular traffic, the preferred method of installation is for the curb to rest on the compacted aggregate. Partial-depth precast concrete edge restraints may be used for residential and light-duty commercial applications. These precast units are anchored on a compacted aggregate base with steel spikes.
| Construction tips |
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| When the gap between the pavers and the edge restraint exceeds 10 mm (0.39 in.), the space should be filled with a cut paver. A clean appearance is possible when a running course is placed parallel to a straight, flush edge. This detail can reduce incidental chipping of cut pavers. |
Edge restrains formed on site
Poured-in-place concrete curbs or combination curb and gutters make suitable restraints for pavers. Exposed concrete edges should have a 3-mm (0.12-in.) radius edge to reduce the chance of chipping. As with precast edge restraints, the side of the curb should extend well below the sand bedding course.
Other edge restraint considerations
Pay careful attention when compacting pavers along the edge of the restraint material. Over time, settlement can occur if the pavers are not compacted properly. Using a plate compactor and a little extra care around these areas can ensure a quality installation.
