An edge restraint is the fixed perimeter that stops a paved surface from spreading sideways. Without one, interlocking paving has nothing holding it in: the outer bricks creep outwards a few millimetres a year, the joints open, the sand washes out, and the failure works its way inwards from the edge until the middle of the driveway is loose too.
It is the least glamorous line on a paving quote and the one most often left off. When we are called to look at paving that has “gone wavy” after three or four years, the edge is the first thing we check, and it is usually the answer.
Why paving spreads without one
Interlocking paving is a flexible surface. There is no mortar between the bricks — the strength comes from load spreading sideways through sand-filled joints into the surrounding bricks and down into the base. That only works if the sideways push has something to push against.
Every time a car wheel rolls over the surface it applies an outward force. Every time it brakes or turns, more. Contained by a solid perimeter, that force disperses and nothing moves. Unrestrained, the outermost brick has nowhere to transfer it, so it shifts a fraction. Now there is a gap. Sand escapes into the gap. The next brick in has a fraction of room, so it shifts too.
Cape Town speeds this up in two specific ways. Our winter rainfall arrives in concentrated cold-front downpours between roughly May and August, and running water is very effective at flushing loose joint sand out of any opened edge. And on the Cape Flats and West Coast sand belt — Parklands, Table View, Milnerton, Blouberg — the surrounding ground offers almost no lateral resistance, so an unrestrained edge simply slides into the sand beside it.
The types of edge restraint, and where each belongs
| Type | How it works | Best for | Weakness |
|---|---|---|---|
| Concrete haunching | Wedge of concrete cast against the outer brick, below finished level | Driveways, most Cape Town jobs | Fails if cast on unprepared ground or too shallow |
| Precast kerb or edging | Kerb unit bedded and haunched in concrete | Driveway perimeters, drive-over edges | Visible; needs a level line to look right |
| Soldier course on haunching | Row of bricks laid end-on, haunched behind | Where you want the restraint to look deliberate | Only as good as the concrete behind it |
| Plastic/composite edging with spikes | Strip pinned into the base with steel spikes | Patios, pathways, light traffic | Not adequate for vehicles on soft ground |
| Existing wall or building | Structure acts as the restraint | Any edge that abuts it | Only counts if the paving is tight to it |
| Steel edging | Rolled steel strip pinned in place | Modern garden edges, curved beds | Cost; corrosion in coastal salt air |
Concrete haunching: what a correct one looks like
Most Cape Town driveways are restrained with a concrete haunch, and the details matter more than the material:
- It sits on the base, not on loose soil. The base layer must extend beyond the paved area so the haunch bears on compacted stone. A haunch cast on soft garden soil moves with the soil, which defeats the point.
- It is deep enough. A thin lip of concrete smeared against the last brick is decoration. The haunch should rise against a meaningful proportion of the brick’s depth and have real cross-section behind it.
- It finishes below the surface. Roughly 25–40mm below the top of the brick, sloped away, so grass or mulch covers it and you never see a grey collar around your driveway.
- It is continuous. Gaps become the failure point. Water finds them, sand leaves through them.
- It is cast before the joint sand is compacted in. Sequence matters. Restrain first, then vibrate and sand the field.
Where edges fail most often
- The street entrance. Every vehicle crosses it, usually while turning. This is the highest-stress metre of the whole driveway and it needs the strongest detail you can build.
- Against a lawn or bed. No natural restraint at all — the paving is effectively floating next to loose soil.
- The bottom of a slope. In Hout Bay, Vredehoek, Constantia and the upper Plattekloof streets, gravity plus braking loads push everything downhill and it all arrives at the lowest edge.
- Around drains and manholes. Small cuts with little bricks around them, and often no restraint whatsoever.
- Curves and circles. Curved edges are fiddly and get skipped. A radius needs more restraint, not less.
- Beside a pool. Constant wetting undermines an unrestrained perimeter fast, which is why proper edge and drainage detail is central to how we approach swimming pool paving.
Why cheap quotes leave it out
Edge restraint is buried work. It costs concrete, extra excavation width and a day or so of labour, and once the job is finished the client cannot see whether it is there. That makes it the easiest thing to delete from a quote to win a price comparison.
Two quotes for the same 60m² driveway can differ by several thousand rand purely on the perimeter detail, and the cheaper one looks identical on handover day. The difference shows up in year three. Our guide to cheap paving in Cape Town covers which savings are genuine and which are borrowed from the future — edge restraints are firmly in the second category.
What to look for on a quote: a line item that names the restraint type and where it runs. “Concrete haunching to all open edges” is a real specification. Silence is not. If it is not written down, assume it is not priced, and ask.
Can a failed edge be fixed?
Usually yes, and it is far cheaper than a full relay if you catch it early. The affected bricks come up, the base is corrected and extended past the perimeter, a proper haunch or kerb goes in, and the same bricks go back down and get re-sanded. On a driveway edge that has only moved a brick or two deep, this is localised work.
Leave it and the failure migrates inwards. Once the middle of the surface is loose and the base has been washed and rutted, you are into a lift-and-relay of the whole area — typically R380–R650 per m², which is roughly 40–60% of a full replacement. Our paving maintenance guide sets out what to check each autumn before the rain arrives.
If your edges have started opening up, send us photographs of the perimeter and we will tell you honestly whether it is a repair or a relay. You can reach us through the contact page, and our our paving repair service page explains how we build the perimeter on a new installation.
Quick answers
What is an edge restraint in paving?
It is the fixed perimeter — usually concrete haunching, a precast kerb or a haunched soldier course — that stops interlocking paving spreading sideways under load. Without it the outer bricks creep outwards, joints open, sand washes out and the failure spreads inwards.
Do patios and pathways need edge restraints too?
Yes, though the detail can be lighter. Foot traffic applies far less outward force than vehicles, so pinned composite or steel edging is often adequate on a patio or path. Anything a vehicle crosses needs concrete.
How do I know if my edge restraint has failed?
Look along the perimeter for bricks that have shifted out of line, joints that have opened wider at the edge than in the middle, joint sand that keeps disappearing after rain, and grass or soil creeping under the outer bricks. Those are edge failures, not surface problems.