Roots follow water and air, not concrete
It is easy to assume a root deliberately attacked your driveway, but roots are not out to wreck your hardscape, whatever the cracks look like. A root grows toward whatever offers the three things it needs most: water, oxygen, and loose soil it can push through. The gap beneath a slab very often has all three at once, namely shelter from the dry, baking surface, small air pockets in the fill, and moisture that lingers under the concrete long after the open ground nearby has dried out.
So the root finds that favorable space and settles in. Then it does the one thing roots do, which is thicken, year over year, as the tree grows. A root that started pencil-thin can become as wide as your wrist over a decade. With soil packed solid below and a rigid slab above, the only direction left is up, and a slab of concrete loses that slow, patient contest every single time.
The usual culprits around Portland
Most of the lifting we see across the metro traces back to a few predictable causes. The biggest is simply the wrong species planted too close to paving, fast-growing, shallow-rooted trees set within a few feet of a driveway, walkway, or foundation, with no root barrier in between. That is the classic setup for an expensive surprise a decade later.
Our soil and climate play a part too. Heavy clay forces roots to stay shallow and spread sideways rather than dive down, which puts them right at slab depth. And the wet-then-dry Portland year trains roots to chase the lingering moisture under hardscape during our long dry summers. The damage builds invisibly for years and then seems to appear all at once, which is why a tree that has been a quiet, welcome neighbor suddenly becomes a costly problem.
The damage builds invisibly for years, then seems to appear all at once. By the time you see it, the root is wrist-thick.
Signs worth watching for
You can usually catch this early if you know what to look for. Hairline cracks that widen a little each year, a slab corner that has begun to tilt or rock underfoot, a section of driveway lifting into a low ridge, or a seam in the sidewalk that suddenly catches your toe are all early tells. Indoors, doors near an exterior wall that start to stick can occasionally point to root pressure on the foundation, though that has many causes.
The clearest warning is at the base of the tree itself. When you see surface roots ridging up through the lawn, that is the visible part of a much larger system, and it usually means more roots are quietly working their way under whatever hardscape sits nearby. Catching it at the hairline-crack stage gives you cheap options. Left alone, a lifting slab becomes a genuine trip hazard, a liability if it is a public sidewalk, and eventually a full tear-out and replacement.
What you can actually do
Your choices run from least to most involved, and the right one depends on how valuable the tree is and how bad the damage has gotten. The gentlest option is root pruning, cutting the offending root cleanly and installing a proper root barrier afterward so it does not simply grow back along the same path. Done by someone who knows what they are doing, it can buy a slab many years without seriously harming a healthy tree.
Improving drainage so the soil under the paving is less appealing to roots helps too, as does grinding and replacing just the lifted section of concrete once the root issue is handled. But sometimes the honest answer is the hard one: the tree is the wrong species in the wrong spot, it will keep doing this no matter how many roots you cut, and removal is the only permanent fix. When that is the case, taking it out and grinding the stump and surface roots lets you finally make a repair that lasts.
Planting smarter next time
If you do end up replacing the tree, you get a clean slate, so use it. Give the new tree real room to mature, choose a species whose mature size and root habit suit the space, and keep it a sensible distance from paving, the house, and the sewer line. A root barrier installed at planting time is cheap insurance against repeating the whole cycle.
And whatever you plant, get your timing right for the Willamette Valley seasons so the tree establishes a strong, deep, well-behaved root system from the very start. A tree planted well, in the right spot, at the right time of year, is a tree that stays a quiet neighbor for the next fifty years.
When a tree truly is the wrong tree in the wrong place, taking it out and grinding the stump and surface roots clears the way for a clean, lasting repair instead of patching over something still alive and growing.