A web of small, interlocking cracks is a warning about what lies under the surface, and a coat of sealer will not change it. Here is how to recognize alligator cracking, why sealing fails and what to do instead.
In This Article
What alligator cracking is
Alligator cracking, also called fatigue cracking, is a network of connected cracks that looks like reptile skin or chicken wire. It forms when the asphalt layer flexes over and over on a weak support. The base beneath may be thin, poorly drained or saturated, or the asphalt layer may be too thin for the loads it carries.
Southern Ontario winters make it worse. Water that collects in a weak base freezes, heaves and then thaws into a soft, unsupported layer, and a car crossing that layer flexes it again. Small cracks join into a web, and the web breaks into small pieces.
How to tell it from ordinary cracking
| Check | Ordinary cracking | Alligator cracking |
|---|---|---|
| Pattern | Single lines, or a few spread out | Many cracks joined into a web with small, block-like cells |
| Location | Anywhere, often along joints and edges | Often in the wheel paths and where cars stop and turn |
| Surface shape | Level | May sag, rut or dip inside the cracked area |
| Feel underfoot | Firm | Springy or soft in places |
| After rain | Cracks dry out | Muddy water may seep up through the cracks |
Two or three of the right-hand signs together point to a problem below the surface.
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Why sealing cannot fix it
Sealcoat is a thin film with no structural strength. It cannot hold a moving surface together, and it does not touch the weak base underneath. The pieces keep moving, the film cracks along the same lines within a season or two, and you have spent money on a darker version of the same problem.
Crack filling fails for the same reason. Filler bonds to the walls of a crack, and in an alligator pattern every wall is on a piece that moves. The guide to crack filling before sealing explains why cracks that are too large or too numerous need patching, not filling.
Your options, from a patch to replacement
| Option | When it fits | Trade-off |
|---|---|---|
| Cut-out patch | The failed area is small and the rest of the driveway is sound | The patch shows, and it must reach down through the failed base |
| Repair, then resurface | The failed spots are fixed and the remaining surface is tired but firm | A new layer over untreated weakness will crack again |
| Full replacement | Failure is widespread, or the base and drainage are poor | The largest job, but it fixes the cause |
| Watch and wait | The area is small, firm and not spreading | It may grow, so photograph and re-check |
Whichever route you take, fix drainage as part of it. If water still collects in the base, the new surface will fail the same way. If you are replacing the driveway, best driveway materials in Ontario compares the alternatives.
Holding the line until repairs happen
Repairs are often scheduled for the next good season, so a few interim steps stop a bad patch from getting worse.
- Keep heavy loads off it. Delivery trucks, trailers and moving vans concentrate weight on a weakened area.
- Route water away. Redirect downspouts and clear anything that sends runoff across the cracked zone.
- Mark soft spots with bright paint, so family members and delivery drivers know where they are.
- Patch hazards only. A cold-patch product can fill a new pothole for a while, following its label, but it is a temporary measure.
- Be gentle with snow tools. A steel blade or shovel edge digs into loose pieces and rips them out.
Plan repairs for dry, settled weather, not the middle of a freeze-thaw winter, when the ground is soaked or frozen and a lasting repair is hard for anyone to make.
How to decide, and who to ask
- Measure the affected area and compare it with the whole driveway. A small patch is a different story from a large fraction of the surface.
- Look at drainage. Note where water sits and where downspouts and grading send it.
- Get an assessment from a paving contractor, and if the answer is expensive, a second opinion.
- Seal afterwards. Once the structure is sound, a coat protects the repair and the rest of the surface.
D&D Home Services does driveway sealing, not paving, so structural repairs belong with a paving contractor. Quotes for sealing are free and confirmed in writing before work begins, and they are worth requesting once the surface is sound.
Key Takeaways
- Alligator cracking is a web of connected cracks caused by a weak or saturated base, not by surface wear.
- Check for a web pattern in the wheel paths, a sagging surface, a springy feel and muddy water seeping up after rain.
- Sealer and crack filler cannot fix it because the pieces keep moving and the base is untouched.
- Options run from a cut-out patch to full replacement, and drainage must be fixed in every case before any new coating.
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