Why is the edge of my concrete driveway breaking off?

Why is the edge of my concrete driveway breaking off?

The edge breaks because it is held on one side only. A panel in the middle of the drive has concrete around it and ground under every inch. The long edges and the outside corners have lawn on the open side, and once that lawn sinks below the slab, the edge is hanging over air. Then a tire finds it. Any read on driveway repair in Henderson starts with what the ground beside the slab has been doing.

Most edges in town go the same way. The dirt beside the concrete drops an inch, water sits in the gap and softens the ground under the outer few inches of slab, and the next wheel that rolls over it snaps off a piece. A driveway that has stayed whole in the middle for twenty years can lose an edge in a couple of winters once that starts.

What does the broken edge look like, and what does each kind tell you?

Walk the drive from the street to the garage along both sides and look at where the concrete ends. The shape of the break tells you whether the ground beside the edge gave out or the concrete itself is wearing away, and plenty of driveways show both on different sides.

• Chunks broken off the side, a hand’s width or so, along a stretch where the lawn sits an inch or two below the concrete. The ground went first and the edge followed it down.
• An outside corner snapped off at the turn into the garage or onto a parking spot. A tire has been cutting that corner with nothing beside it.
• A long crack running down the drive about a foot in from the edge. The whole edge strip is letting go as one piece, and it usually tips a little toward the lawn.
• Crumbling all along the lawn side, a bit worse every year, with no clean break anywhere. That one points at the concrete, often a slab too thin to carry its own edge.

Where the lawn has dropped, slide a finger under the edge. If it goes in past the first knuckle, the ground that held that edge up is already gone.

Why does the lawn end up lower than the driveway?

The lawn drops a little every year and the concrete stays where it was poured. Rain carries topsoil off the strip beside the slab and the mower packs down what is left. Underneath, the clay most Henderson lots sit on shrinks back from the concrete in a dry August and opens a crack of air along the edge.

On a lot of driveways the edge never had much beside it to begin with. When the forms come off, the trench they leave is supposed to be filled with dirt to the top of the slab and packed down. If a little topsoil gets raked into it instead, the first hard rain carries it off, and the edge spends the rest of its life standing proud of the grass.

That gap turns into a channel. Water runs along it, soaks in at the edge, and softens the soil under the outer foot of the slab, the part that was carrying the load from the side. A whole panel sitting low is something else, a void under the slab, and that is covered in why a slab sinks and what lifting fixes.

Why does it break where cars cut the corner?

An outside corner takes the most weight with the least under it. On a turn into the garage or onto a parking spot, the rear wheels track inside the front ones, so a driver who cuts the turn puts a rear tire on the corner, or half off it, every day. A corner has open ground on two sides and nothing to share the load with.

The East End’s old single-car drives get it worst. A lot of the ranches off Green Street and Zion Road were built with a drive one car wide, and once a second car lives at the house, somebody runs a wheel along the edge or off it to get by. Smaller loads work the same spot, the mower wheel dropping off the edge on every pass and the trash cart riding it out to the street each week.

When a second car is the reason, rebuilding the old edge only sets it up for the same wheel, and that is when the real fix is a wider driveway.

Is a crumbling edge a sign the whole driveway is going?

Not when the edge is the only thing failing. If the middle of the drive is flat and solid underfoot, a broken edge is a local problem with a local repair, and the rest of the slab has years left in it.

It reads differently when the edge crumbles the whole length on both sides and the slab is thin. Concrete poured thin over loose fill loses its edges first, which is part of the story behind why so many 1990s subdivision driveways came out under three inches. On a drive like that the edge is the first sign of a slab past saving, and the question turns to when a Henderson driveway needs replacing.

Can a broken driveway edge be patched?

A patch will not hold on an edge. Troweled onto a broken side, it has nothing to grip on the lawn side and nothing firm under it, so it sits on the same soft ground that let the original edge go. The next tire that rolls onto it breaks it off again, usually along the line where the patch meets the old concrete.

The repair that lasts starts with a saw. The crew cuts a straight line back into sound concrete, past the cracking or the crumbling, and breaks out the damaged strip. The ground under it is rebuilt and compacted, the new edge is tied into the old slab with steel, and a fresh strip is poured and finished to the old surface. The steel belongs on this job since the new strip is a rebuilt piece of the old slab rather than a separate pour set beside it. When the forms come off, the lawn gets backfilled up to the top of the new edge and packed.

The new strip will be a lighter gray than the rest of the drive for a long time, for the reasons on why a repair never matches the old slab.

What keeps a repaired edge from breaking again?

Ground kept up against it. Backfill to the top of the slab, sloped so water runs off onto the lawn instead of along the edge, and top it up when it settles. After a winter of freezing and thawing twenty times over, the dirt along a driveway edge is usually the first thing to have dropped, and a spring look catches the gap while it is still small.

Where cars cut the turn, the new strip can be built for the wheel. A wider edge at the corner gives the tire somewhere to land. A thickened edge, poured deeper along its outside line than the rest of the slab, carries the wheel that does drop onto it. And a corner rounded into a curve, or flared wider at the turn, takes away the sharp point the tire kept catching. Watch the next time someone pulls in. Wherever the rear tire leaves the concrete is where the new edge needs the extra width.