Why court cracks come back, and what actually stops them

A court owner once showed me a crack that had been filled three times by three contractors, and he wanted to know what was wrong with the fillers. Nothing was wrong with the fillers. The crack was doing what cracks do, and the fillers were doing what fillers do, and nobody had told him the difference between filling a crack and repairing one.

A crack is where the slab moves

Asphalt is not a rock. It expands in July and shrinks in January, and the ground under it, which around here is clay, swells when it is wet and heaves when it freezes. All of that movement has to go somewhere, and a crack is where it goes. Once a court has a crack, the two sides of it move apart in winter and back together in summer, by a fraction of an inch, every year, forever. The crack is not a flaw in the surface. It is a joint the court made for itself.

Which is why filling it does not last. You clean the crack out, you fill it with something flush, you paint over it, and in January the two sides move apart and the filler, which has no stretch in it, cracks along one edge or both. Water gets into the new crack, freezes, and opens it wider. By the second spring the line is back through the color, usually a little wider than before, and the owner thinks the filler failed. It did exactly what a rigid thing in a moving joint does.

Water does the real damage

The crack itself would be a cosmetic problem if it stayed dry. It does not. Rain runs into it, and in Northeast Ohio the water in a crack freezes and thaws something like forty or fifty times between November and March. Each freeze expands the water about nine percent and pushes the edges of the crack apart; each thaw lets the water drain deeper and carry a little fine material out of the base. After a few winters the crack is wider, the edges are crumbling, and the base under it has a soft spot that will become a depression. That is the cycle the owner was watching, and the fillers were not even slowing it down.

Bridging instead of filling

The repair that holds is one that lets the crack keep moving without showing it. We use a fabric-membrane system, and the idea is simple: the crack is cleaned and filled flush so there is a flat bed, then a strip of flexible fabric membrane wider than the crack is bonded over it in acrylic binder, and the edges are feathered out with patch binder until there is no ridge. When the slab moves in January, the membrane stretches a hair and the color coat on top of it stays in one piece. The crack is still there under the fabric, doing its job as a joint. Nobody sees it.

A membrane repair done in autumn lasts, in our experience, about as long as the color on top of it, five to eight years under a Northeast Ohio court. The makers claim longer; the ASBA says plainly that cracks eventually reappear or new ones form. Anyone telling you a crack is gone for good is selling something.

When bridging is not enough

A membrane handles a crack up to about an inch that runs through otherwise sound pavement. It does not handle three other things, and you need to know which you have.

• Alligator cracking. Cracks in a pattern of blocks or scales over an area mean the base under that area has failed, usually from water. Filling or bridging each crack is a waste; the area has to be cut out and the base rebuilt, or the whole court overlaid.
• Heaves. A section that lifts every winter and settles every summer is sitting on something that freezes: a wet clay pocket, a buried stump, a drain. It has to be dug out and the cause removed.
• A court out of plane. When the slab has settled so that water sits in the middle or runs the wrong way, cracks are the least of it. That court is an overlay or a rebuild, and an honest contractor says so on the first walk.

Overlay, or post-tension

An overlay is a new lift of asphalt over the old court with a stress-relief fabric between them, which slows the old cracks from reflecting through; it is a new court on an old base and it lasts fifteen or twenty years. A rebuild starts over. For an owner planning on forty years, a post-tensioned concrete slab, pulled tight with steel cables after it cures, is the court least likely to crack in the first place; I wrote about when that is worth the money.

What to do this year

Chalk every crack in September. Have the working ones bridged in October, before the water gets in for the winter. Fill the hairlines at the same time. Flood-test the court afterward and fix any birdbath. Then budget for the resurfacing when the color wears, knowing the cracks will not be the reason. That is the whole program, and it is the difference between a court that gets filled three times and one that gets repaired once.