Why is a random section of my asphalt driveway heaving up?

Two inches in two weeks is way too fast for actual tree root growth, but don't rule out that red oak entirely. If you've had heavy rains recently following a dry stretch, a thick root alredy riding right below the crushed gravel can soak up water and swell dramatically. High-plasticity expansive clay behaves the exact same way. If water found an edge or seam to wash under the driveway, the subgrade will swell into a localized **frost-free heave**, expecially under thin or aging asphalt.

Another strange but surprisingly common culprit for sudden ridges like this is subterranean fungus. If an old oak root died years ago, fungal fruiting bodies feeding on the rotting wood generate massive hydraulic pressure as they try to push to the surface. They can easily lift hot mix an inch or two in just days before finally rupturing thru.

Whatever you do, don't wait untill spring. If you leave an open hairline crack with a two-inch hump right where your car parks, winter rain and the first hard freeze will shatter that asphalt into loose chunks. Grab an angle grinder with a diamond masonry blade and make a clean, rectangular relief cut right along the peak of the ridge. Pop the asphalt cap off to see what's physically pushing up. If it's a root that wedged up against the base, you can notch out a section with an axe or reciprocating saw, re-tamp the gravel base, and patch it with commercial cold patch to get you through winter. If it's soaking wet clay or standing water, you'll know imediately that you need to trench a small diversion swale along the driveway edge before the ground freezes solid.

Had the exact same sudden heave a few years back. Turned out to be a pinhole leak in my main water line running right under the pad. The pressurized water turned the subgrade into a slurry bubble and jacked the blacktop right up in a matter of days.

Go shut off every faucet in the house and check your water meter right now. If that little flow indicator dial is spinning even a hair, you're dealing with a plumbing blowout, not a tree issue. Saved myself a massive headache by checking the meter before I started swinging tools.

Check if anyone's had a heavy delivery truck turn around out there lately. If your base layer wasn't packed right or got a bit soft, a massive axle load can cause a shear failure. basially, the weight punches down under the tires and shoves the dirt and asphalt right up next to it into a ridge.

Happened to my neighbor when a heating oil truck backed in. He didn't even notice the shallow tire rut at first, just the crazy hump that suddenly popped up right where his wife parks.

Don't overlook critters. Seen groundhogs push up a ridge just like that come late fall looking for a dry den under the heat of the blacktop. They'll excavate out a chamber and pack displaced gravel right up against the underside untill the asphalt stretches. Grab an old four-foot stick of half-inch rebar and probe the turf right along that edge. Give it a few light taps with a hand sledge. If the rod suddenly drops six inches into thin air, you've got yourself a tenant. Back in the day we'd flood the run with coarse limestone screening and water it in solid before touching the blacktop.

Before you go hacking a giant trench in the blacktop, drill a quick pilot hole right at the crown and snake a Depstech DS520 borescope down there. Takes five minutes and you'll see whether you're hitting wood, mud, or a void without completley destroying the driveway first.

If you do cut it open to clear whatever is underneath, skip the standard cheap cold patch and grab a bucket of Aquaphalt 6.0. It cures rock-hard with water in fifteen minutes so you can park your car right back over it without it dishing out all winter.

Quick update — I checked our water meter with everthing shut off inside like suggested, and the little leak dial isn't spinning, so thankfully no broken pipe. But while probing the lawn right along the edge of the heave, a long screwdriver dropped straight into empty space about eight inches down. If this is a burrowing critter, will packing gravel down there just force it to dig another chamber under the asphalt?