Edge restraint and joint sand: the details that hold it together

Why edges fail

A paver field is held in compression by its perimeter. Load a unit near an unrestrained edge and it pushes outward; the joint opens, sand escapes, and the next unit follows. Once the outer course moves, the failure travels inward.

The base must extend at least 6 inches beyond the paver edge so the restraint spikes bite into compacted aggregate, not soil. Restraint spiked into loose ground is decorative.

Choosing restraint

Spiked polymer restraint with 10-inch galvanised or steel spikes at 12-inch centres is the standard for patios and walkways. Aluminium restraint is used where the edge must hold a tight radius. For paver driveways, a concrete haunch — a wedge of concrete against the outer course, below finished grade — is the most durable detail.

Whatever the type, the restraint sits below the top of the paver so it is invisible once the surrounding grade or turf goes back.

Installing polymeric sand correctly

Polymeric sand fails almost exclusively through installation error. The sequence is fixed: the paver surface must be bone dry, sand is swept into joints until they are full to within about 1/8 inch of the surface, the surface is blown clean of every grain, then the field is vibrated with a plate compactor and roller pad so the sand settles, then topped up and blown clean again.

Only then does it get watered, in light passes, following the manufacturer's timing. Watering with sand residue on the paver faces is what produces the permanent white haze people blame on the product.

• Joints must be dry before sanding
• Blow the surface completely clean before any water touches it
• Water in short passes — flooding washes the binder out of the joints

Maintenance

Expect to top up joint sand every 5-10 years, sooner in areas that get pressure-washed. Pressure washing at close range strips joints faster than any traffic does; use a fan tip at distance and re-sand afterwards.

Efflorescence — a white bloom on new concrete pavers — is salts migrating out of the units. It weathers off in 6-18 months and does not indicate a fault.