Gravel Driveway Ruts And Potholes

What's happening?

Paving Expert explains that where a loose gravel surface carries people or vehicles, a sub-base is needed as the load-bearing layer, and the gravel is only a surface dressing. Gravel by itself is useless at carrying a wheel, which just sinks in. It recommends a gravel depth of at least twice the stone size, so around 25mm for 12mm gravel, and says 25-40mm is about ideal, because a deep layer becomes unstable and renders the surface virtually unusable. For self-binding gravel it recommends a sub-base of Type 1 aggregate, 125-175mm for regular vehicles, compacted to refusal, with adequate falls. A geotextile placed between the sub-base and a self-binding gravel acts as a slip membrane and encourages soft spots and potholes.

What usually causes it?

• A sub-base that is too thin or soft for the vehicles using it
• A gravel layer that is too deep, so wheels sink and the surface becomes unstable
• Poor compaction of the base or the self-binding gravel layer
• A geotextile placed over the sub-base under a self-binding gravel, creating soft spots
• Inadequate falls, so water collects and softens the base
• Heavier vehicles than the drive was built for

Is it dangerous?

No. Ruts and potholes are a nuisance and can damage tyres and suspension. Paving Expert says potholes should be repaired as soon as possible, because they never get any smaller.

Can I fix it myself?

Work out whether it is a surface or a base problem. If the gravel is simply thin or scuffed, Paving Expert says to top it up to 25-40mm and compact. For a pothole in a self-binding gravel, it describes cutting out the damaged area with at least 100mm spread beyond the pothole, removing the aggregate to expose the sub-base, then filling with fresh self-binding aggregate and compacting. Soft spots mean the base is the problem, and tipping new stone on top will not last. It says light plate compactors are unlikely to suit self-binding gravel and a heavier machine or roller is needed. A gravel-filled grid is a separate system built to its maker's design: Terram's notes for its grid say the sub-base thickness depends on the ground strength, with substantial edge restraints and clean angular aggregate.

When should you call a driveway and patio installer?

Call a driveway contractor when ruts keep returning, when the base is soft in several places, when the drive carries heavy vehicles, or when the whole surface needs rebuilding with a proper sub-base, falls and compaction.

What will the driveway and patio installer actually do?

• Dig test holes to check the sub-base depth and condition
• Cut out and rebuild soft spots with compacted Type 1 sub-base
• Relay the gravel or self-binding gravel layer to the right depth and compact it
• Correct the falls and edging so water drains and gravel stays put
• Check that no geotextile sits between the sub-base and a self-binding gravel

Who fixes this

• Driveway repair
• Gravel driveway installation

Questions people ask

Sources & References

1. Paving Expert: gravel, cinder and hoggin paths and drives
2. Paving Expert: self-binding gravels
3. Terram: design notes for a gravel-filled cellular paver surface