Driveway Sinking at the Edges: Why Borders Give Way First

On block paving the outside course should be haunched, meaning it is bedded and backed with concrete so it cannot move sideways. Where that haunching was left out or was skimped to a thin smear, the edge blocks push outwards every time a car turns on them. Once they move, the jointing sand runs out and the whole matrix loosens.

The other frequent cause is soft ground next to the drive. A lawn, a border or a filled service trench alongside the paving gives the sub-base nothing to bear against. The stone spreads sideways under load and the surface drops to follow it.

On resin and tarmac drives the same principle applies, but the symptom is different. Instead of individual blocks moving you get a crumbling lip along the edge, then cracking a few inches in, because the surface layer has lost the support it was bridging over.

Water leaving a drive at its lowest edge will carry fines out of the sub-base with it if there is nowhere designed for it to go. Over years that quietly hollows out the shoulder of the drive, and the first you know about it is a dip along the run.

Downpipes discharging onto or beside a drive make this much faster. So does a gully that has silted up and now overflows across the paving instead of taking the water away.

Check where the water goes during heavy rain. If it runs off the edge into a soft border and that border is sinking too, the drainage needs correcting as part of the repair, or the same dip will come back.

Clearing gullies and channel drains, extending a downpipe so it discharges into a drain rather than onto the paving, and topping up jointing sand along a loosened edge are all sensible homeowner jobs and they slow the problem down.

What is not worth attempting is re-haunching a driveway edge with a bag of ready-mix. Haunching only works when it is placed against a properly compacted shoulder at the correct depth, and a shallow collar of concrete simply breaks away and gives you the same failure with more to dig out next time.

We lift the affected edge course and enough of the adjoining paving to see what the base is doing, dig out the soft shoulder, and rebuild with a compacted stone base and a properly haunched edge restraint set in concrete. Where the failure has been caused by water, the repair includes correcting the falls or adding drainage so it leaves the drive on purpose rather than by accident.

If the sinking has already spread well into the drive, we will tell you that a partial repair is a stopgap. Where a rebuild is the right call we say so and price both, so the decision is yours with the facts in front of you. All of it carries our ten year guarantee.