What are edge restraints (kerbs and haunching)?

Edge restraints are structural barriers fixed to the perimeter of block paving installations. They work by holding the outer rows of blocks in place so the entire paved surface resists lateral movement and spreading caused by foot traffic, vehicle weight, or ground settlement.

The two main types are kerbs (typically precast concrete or natural stone blocks set vertically along the edge) and haunching (concrete or mortar applied to the outer face and often the back of the final row of blocks). Both prevent the paving from creeping outward and creating uneven surfaces where blocks tilt or separate.

Edge restraints matter because block paving is laid without rigid mortar between individual blocks, which allows flexibility underfoot but also means the outer courses need containment. Without restraints, blocks at the perimeter can shift under load, creating trip hazards, allowing weeds and water to penetrate the gaps, and eventually requiring costly repairs. In driveways, this movement can lead to the loss of fall and drainage function.

Kerbs suit formal boundaries and provide a finished edge detail; haunching works well where a softer transition is needed or where the paving meets soil directly. Both must be installed during or immediately after the paving work to be effective.