Hole Opened Overnight in Your Driveway: Sinkhole or Pothole?
Yesterday the driveway was fine. This morning there is a hole in it — deeper than any pothole you have seen, with edges that drop away instead of crumbling. Your first thought is a pothole. Your second thought, standing over it, is that something under the ground has given way.
Both thoughts can be right, and the difference matters. A pothole is a surface problem with a surface fix. A washout is a ground problem, and patching over one wastes money while the real cause keeps eating the base. Here is how to tell them apart, what to do in the next hour, and the order to fix things in.
Pothole or washout: read the shape, the depth and the speed
A normal pothole announces itself. It starts as a crack or a shallow scab, grows over weeks of rain and traffic, and stays roughly saucer-shaped: wide mouth, shallow bowl, ragged crumbling edges. If you think back, you probably saw it coming.
A washout behaves differently. Three signs point away from a simple pothole:
Shape. Washouts tend to be rounder and steeper-sided, sometimes narrower at the mouth than they are underneath. If the hole is deeper than it is wide, be suspicious.
Depth. A pothole bottoms out on the basecourse, usually within 50-100mm. A washout keeps going. If you can push a broom handle in past 200mm and the bottom feels soft or hollow, the base has been carried away, not worn away.
Speed. Potholes take weeks. A hole that appears overnight, in one spot, with no cracking around it, almost always means material moved underground.
The distinction is not academic. Filling a washout with asphalt just gives the void a new lid.
The broken-pipe signature
The most common cause of a sudden washout under an Auckland driveway is a failed pipe — stormwater, wastewater or the water supply lateral — washing the fine material out of the base every time it runs. The fines go first, the coarse metal loses its interlock, and eventually the surface drops into the gap.
Watch for these signs over the next day or two:
The hole keeps growing after rain. A pothole grows at its edges. A washout deepens and undermines, because each rain event flushes more material away.
Water sounds. Trickling or running water near the hole when nothing is turned on points to a live leak.
Low water pressure or a jumpy water meter. If the meter ticks over with every tap in the house off, the supply pipe is leaking — possibly straight into your driveway base.
Damp ground in a dry week. Persistent moisture at one spot when everything else has dried out is water arriving from below.
Any of these, and your first call is a drainlayer or plumber, not an asphalt crew. Standing water on the surface tells its own story too — our guide to what a persistent puddle is telling you covers the slower version of the same problem.
The Auckland special: what might be buried under your driveway
Older Auckland sections hide more underground history than most owners realise. Before reticulated services reached the suburbs, properties ran on septic tanks and soakage pits, and plenty were simply abandoned in place when the mains arrived. Decades later, a timber lid rots, a brick chamber collapses, or a scoria-filled soak pit finally consolidates — and the driveway above it drops.
Volcanic parts of the isthmus add scoria voids and old quarry fill to the list. If your house predates the 1970s and the hole is deep, round and stable in dry weather, an old buried structure is a live possibility. A drainlayer with a CCTV camera can confirm what is down there before anyone prices the surface repair.
What to do in the next hour
Sudden holes deserve respect until you know what caused them. The ground at the edge may be undermined further than it looks.
Cone it, or park a wheelie bin over it, so nobody drives or steps into it — especially at night.
Keep vehicles off that section of driveway. A car wheel can turn an undermined edge into a much bigger collapse.
Probe from a distance with a broom handle or garden stake. You want depth and softness, not a close-up inspection from the rim.
Cover it with a weighted board if children use the area.
Photograph it, with something for scale. Dated photos help every conversation that follows, from the drainlayer to the insurer to the repair quote.
Fix it in the right order: cause, base, surface
Whatever the diagnosis, the repair sequence is the same and it only works in one direction:
Stop the water. Repair the failed pipe, decommission the old chamber, or fix the drainage path. Skip this and the new patch fails the same way the old surface did.
Rebuild the base. The washed-out zone gets dug back to sound material and recompacted in layers. This is what a straight pothole patch does not include, and it is where the two repairs genuinely differ in scope.
Reinstate the surface. Cut back to clean edges, hot mix, proper compaction. Done properly, the patch outlasts the driveway around it.
On cost: a standard pothole repair runs from $450 as a fixed price, while a washout depends on what the digging finds — our Auckland pothole repair cost guide covers what moves the number. Either way, the surface stage can be priced before anyone visits.
Send a photo, get an answer
Take two photos: one wide shot showing where the hole sits on the driveway, and one close-up with a size reference in frame — what to photograph for a fixed price walks through it. Mention the depth from your broom-handle probe and anything you have noticed about water.
We will tell you honestly whether it reads as a pothole we can fix straight away or a washout that needs a drainlayer first, and give you a fixed price for the repair — photo quote back within 24 hours, with a dated before-and-after photo report when the job is done. Send us a photo for a fixed price.
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