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Building components · Paving & Decks

Edge Restraint

Explains why an edge element is structural to a flexible paving build-up rather than a trim.

Form:Profile or trimRoles:SupportTerminationProtection

Educational reference entry. What this element has to do, and whether any particular arrangement of it is adequate, depends on the whole assembly, the loading, the exposure, local requirements, the manufacturer's instructions and qualified professional design.

Overview

What a edge restraint is

A flexible paved surface works by its units being held tightly against each other. Load applied to one is shared with its neighbours through the joints, and that only happens while the whole field is confined.

The edge restraint provides that confinement. Without it the outermost units move outward under load, the joints open, the laying course escapes, and the failure works progressively inward from the edge.

Boundaries

How it differs from nearby elements

The distinctions that keep this entry from being a restatement of its neighbours.

  • It is not a kerb. Stone kerb and edging units are a published material entry; the edge restraint is the function, which a kerb is one way of providing.
  • It is not a trim or border. It is a structural element of a flexible paving build-up.
  • It is not a retaining structure. It holds a surface laterally at its own level rather than retaining a height of ground.

Terminology

Common names and aliases

These names describe the same element. The library keeps one entry per component so that a trade term or a regional name never becomes a second, thinner page.

  • edging
  • restraint edge
  • paving restraint

Dependencies

What it depends on

What has to be right elsewhere for this element to do its job.

  • Its own foundation, since a restraint that moves does not restrain.
  • Being continuous around every edge, including where paving meets soft landscape or a building.
  • Extending deep enough to contain the laying course as well as the units.
  • The loading at the edge, which is commonly the most heavily loaded part of a driveway.

Considerations

Topics that genuinely apply here

Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.

Movement

Paving failures very commonly begin at unrestrained edges and progress inward, which is why the edge is where the build-up is most vulnerable.

Durability

The edge of a driveway takes wheel loads at their most concentrated, commonly with the wheel partly off the paving.

Buildability

A restraint bedded on the laying course rather than on its own foundation will move with the paving it is meant to restrain.

Moisture

The restraint must not dam water within the build-up, particularly in permeable paving where water has to leave.

Materials

Commonly formed from

Material families this element is commonly realised in. This states common practice only — it is not a statement that any of these materials suits this component in a particular building, which depends on the whole assembly and on qualified review.

Materials LibraryStone Kerb and Edging →Kerb and edging units are a published material entry designed for this position.Materials LibraryPrecast concrete paving →Concrete edging units are widely used as restraints.Materials LibraryClay Paving Brick →Brick edging courses are used where the restraint should match the paving.Materials LibraryReady-mixed concrete →A concrete haunching behind the edging is commonly what actually provides the restraint.Materials LibraryPreservative-treated timber →Timber edging is met in soft landscape and lightly trafficked areas.

Assemblies

Building systems this element is met in

The role this component fills inside each assembly. A role describes what the element does there — it is not a statement that this component suits that system in any particular building.

Edge and terminationPrimary supportFlexible Paving →Confines the units so interlock is maintained across the whole field.Edge and terminationPermeable Paving →Restrains the surface while allowing water within the build-up to leave.Edge and terminationCellular Confinement Surfacing →Terminates the confined surfacing at its perimeter.Edge and terminationRigid Paving →Finishes the edge of a build-up that acts as one, where the confinement function matters less.

Where it is met

Application contexts

Building contexts where this element is commonly encountered. Association is not recommendation: appearing here does not mean the component suits every instance of that context, or any particular one.

  • External Works
  • Hardstanding

Clarifications

Commonly misunderstood

  • That edging is decorative. In flexible paving it is what makes the surface work at all.
  • That a restraint can sit on the same bedding as the paving. It needs its own foundation, or it moves with what it should be holding.

Conversations

Questions for qualified professionals

Questions worth asking someone with the project in front of them. This page cannot answer them.

  • What foundation does the edge restraint have?
  • Is it continuous around every edge of the paved area?
  • Does it extend deep enough to contain the laying course?
  • In a permeable build-up, does the restraint allow water to leave?

Go deeper

Related Build Design Hub guides

Planning guidance behind the decisions this element involves.

Preparation

Related planning checklists

Owner-side preparation before the conversation where this element comes up.

What this entry does not do

  • No dimension, foundation, material or loading is stated here.
  • Paving edge design follows from the loading and the build-up and is a design matter.

External Works & Paving Elements

The laying course, wearing course, edge restraint, deck framing and guarding posts that make up trafficked surfaces outside the building.

Browse all paving & decks entries →