Installing Kerbstones and Paving Borders: Edging Restraints Explained

Edge restraints are one of the more overlooked elements of a paving project, easy to underestimate because their role is largely structural rather than decorative, but genuinely important to how well a patio or driveway holds together over the years. This guide explains what kerbstones and edging restraints actually do, the main types available, and how to plan and install them properly.

The Short Answer

Edge restraints, including kerbstones and dedicated edging units, provide a solid, fixed boundary around the perimeter of a paved area, preventing individual paving units or sub-base material from spreading, shifting, or working loose over time, particularly under the lateral pressure created by vehicle turning on a driveway. Without proper edge restraint, even a well laid paved surface can gradually lose its structural integrity at the edges, leading to loose joints, sinking, or a spreading, uneven perimeter.

Why Edge Restraints Matter Structurally

A paved surface, particularly one made up of many individual units like block paving or setts, relies on the units being held tightly together to distribute load evenly across the whole area. Without a fixed boundary at the perimeter, this tightly interlocked structure has nowhere to push against, and over time, particularly under vehicle weight or turning forces on a driveway, the edge units can gradually shift outward, loosening the whole surface's structural integrity from the outside in. This is why edge restraint isn't purely a cosmetic finishing touch, it's fundamental to the long-term stability of the paving itself.

Types of Edge Restraint

Kerbstones

Kerbstones are substantial, typically taller edging units, often used along driveway perimeters and boundaries with a road or path, providing a robust, clearly defined edge that can also help manage surface water runoff direction. They're generally set into a concrete haunching for stability, given the structural demands placed on them, particularly where vehicles may occasionally mount or brush against the edge.

Edging Units and Setts

Smaller edging units, sometimes using the same or complementary material to the main paving, provide a less imposing border than full kerbstones while still delivering genuine structural restraint. Our range of edging planks and setts covers options suited to this kind of border detailing across both patios and driveways.

Concealed or Flush Edge Restraints

Where a highly visible border isn't wanted aesthetically, restraint can be achieved through a concealed haunching set just below or flush with the paving surface, providing the same structural function without the more prominent visual line a raised kerbstone or edging course creates.

Planning Edge Restraint Into a Project

Restraint Should Be Planned From the Start

Edge restraint needs to be planned and installed as part of the initial groundworks, not added as an afterthought once the main paving is already laid. Retrofitting restraint into an already completed paved area is considerably more disruptive and less structurally effective than incorporating it from the outset.

Matching Restraint to the Paving Type

Different paving formats have different restraint needs. Block paving and setts, made up of many small units, generally rely more heavily on continuous, robust edge restraint around the full perimeter than large format slab paving, where fewer, larger units create less cumulative outward pressure at the edges.

Installing Kerbstones and Edging: The Basic Process

1. Excavate along the planned edge line. To an appropriate depth for the specific kerb or edging unit and its foundation.
2. Prepare a concrete foundation or haunching. This provides the stable base the edging or kerb unit will be set into and, for kerbstones especially, the structural backing that resists lateral pressure.
3. Set the kerbstones or edging units. Bedding each unit level and to the correct line, checking alignment carefully as you progress along the run.
4. Haunch the back of the edging. Concrete backing behind the edge restraint provides the structural resistance against outward pressure from the paving itself.
5. Allow proper curing time. Before the main paving area is laid against the new edge restraint, to ensure the restraint itself has developed adequate strength.

Edge Restraint and Drainage

Kerbstones in particular often play a dual role, providing structural restraint while also helping direct surface water runoff along a planned route rather than spreading uncontrolled across a boundary. This is worth planning together with your overall drainage design; our guide to drainage and water management for paving slabs covers planning falls and water management that should be considered alongside edge restraint positioning.

Edge Restraint for Driveways Specifically

Given the additional lateral stress vehicle turning places on a driveway's edges, restraint requirements are generally more demanding for driveways than for a pedestrian-only patio. This is particularly relevant when comparing surface types like the ones covered in our guide to driveway slabs vs block setts, since a sett or block driveway's many small units place particular reliance on robust, continuous edge restraint to maintain structural integrity over years of vehicle use.

Common Mistakes with Edge Restraint

• Treating edging as purely decorative. Underestimating its structural role can lead to genuine problems as a paved surface ages.
• Inadequate foundation beneath the edging itself. A kerb or edging unit without proper concrete haunching won't provide reliable long-term restraint.
• Adding restraint as an afterthought. Retrofitting edge restraint into an already laid paved area is far less effective than planning it from the outset.
• Underspecifying restraint for driveways. Driveway edges need more robust restraint than pedestrian patio areas, given the additional vehicle-related lateral stress.

Choosing a Style That Complements Your Paving

Beyond the structural function, edge restraint contributes meaningfully to a paved area's overall appearance. Coordinating edging material and colour with the main paving, whether Indian sandstone or porcelain, generally creates a more cohesive, considered finished result than an edging choice that visually clashes with the primary surface.

Conclusion

Edge restraints, whether robust kerbstones or more discreet edging units, play a genuinely structural role in holding a paved area together over the years, not just a decorative one. Planning restraint properly from the outset, matching it to the specific demands of your paving format and, for driveways, the additional lateral stress of vehicle turning, gives a paved surface the best chance of remaining stable and well defined for decades rather than gradually spreading or loosening at the edges.