A tree that made sense fifty years ago
Silver maples show up constantly in the older parts of Portland and Mitchellville, planted decades back because they grow fast and throw a lot of shade in a hurry, which was exactly what people wanted for a young house with no established trees yet on a bare lot fresh off construction. That same fast growth is what causes problems now that these trees are mature and well past what most homeowners had in mind when they went into the ground originally.
Silver maples are notorious for shallow, aggressive root systems that spread wide and stay close to the surface rather than growing deep. Over enough years, those roots run straight under driveways, sidewalks, and sometimes foundations, and they don't stop growing just because there's concrete in the way of it.
Many of these trees are now well past the age where that growth pattern starts causing visible problems above ground.
Why the roots end up so close to the surface
Part of it is genetics - silver maple roots are built to seek moisture and oxygen near the surface rather than digging deep, which is efficient for the tree but rough on anything paved nearby that happens to sit in the way of that growth. Compacted soil, common in older residential lots where the ground's been driven and walked on for decades, pushes even more root growth upward and outward since the roots have an easier time finding oxygen near the top than fighting through dense subsoil below the surface.
By the time a silver maple is thirty or forty years old, which describes a lot of the trees in Portland's older sections, the root system has usually had plenty of time to reach whatever hardscaping happens to be nearby, driveway or otherwise, and settle in underneath it firmly over the decades of steady, quiet growth nobody paid much attention to at the time.
What the cracking actually looks like
It rarely happens all at once. A driveway develops a hairline crack near the tree that slowly widens over a few seasons as the root underneath keeps growing in diameter and pushing upward against the slab from below. Sidewalks tent upward at a seam. In bad cases, a root running near a foundation can contribute to settling or minor cracking in that structure too, though that's less common around here than driveway and walkway damage tends to be for most properties in the older sections of town closer to downtown Portland.
By the time it's visually obvious, the root causing it has usually been growing under there for years already, working slowly and without much notice until the crack finally shows up on the surface where anyone can see it and start asking questions about what's really going on underneath the slab all along, unnoticed until now by anyone at all.
What removing the tree and grinding the stump does - and doesn't - fix
Taking the tree down and grinding the stump stops the roots from growing any further and eliminates the tree as an ongoing threat to whatever's nearby, whether that's a driveway, a sidewalk, or a foundation close by. It doesn't retroactively undo existing damage to a driveway or sidewalk - that's a separate repair job entirely handled by someone else - but it does stop the problem from getting worse, which matters if you're planning to repave or repour that area anyway down the line.
We grind the stump and the upper root flare down below grade, which clears the immediate area, though roots that have already grown out under the concrete will remain there, gradually decomposing over the following years without causing further movement or additional cracking to worry about going forward from that point on, according to what we typically see on jobs like this around the older parts of Portland.
The short version
Silver maples were planted for fast shade decades ago and now their shallow, aggressive roots are cracking driveways across Portland's older neighborhoods. Removing the tree and grinding the stump stops further root growth, though existing hardscape damage still needs its own repair.