# Alligator cracking: how to prevent it

> Alligator cracking starts with a weak base and water. How to protect the base, keep water moving, and time sealcoat so the pattern never gets started.

Canonical: https://drivewaysealinglab.com/alligator-cracking-prevention/

Last updated: 2026-11-09

Alligator cracking is preventable, but only at the two points where it starts: the base and the water reaching it. Sealing on schedule helps, and it is the cheapest part of the routine, but a coat of sealer cannot rescue a driveway built on a subgrade that cannot carry load.

## What you are preventing

Alligator cracking is a pattern of interconnected cracks forming small polygons, usually 1 to 6 inches across.

It appears when the asphalt flexes repeatedly under load, or when the binder has aged until it can no longer flex at all. In both cases the surface is responding to a problem below or within it.

Prevention therefore has two targets: keep the base strong, and keep the binder from ageing out.

## Target one: protect the base

The base is compacted aggregate over subgrade. It spreads load so the asphalt does not have to.

Four habits protect it.

Keep water out. Water softens subgrade and washes fines out of the base. Every crack, every failed edge, and every low spot is a route in.

Support the edges. An unsupported edge crumbles, water gets under the pavement, and the failure works inward. Our [edge crumbling repair](https://drivewaysealinglab.com/edge-crumbling-repair/) guide covers the fix.

Avoid point loads. A base sized for passenger cars will fatigue faster under repeated RV or truck traffic, particularly in summer when asphalt is soft.

Do not pave over a known soft spot. If a section deflects underfoot after rain, fix the base before any surface work.

## Target two: slow binder ageing

Asphalt binder oxidises under ultraviolet light. The surface goes grey, then brittle, then cracks.

Sealcoat is the countermeasure. At $0.15 to $0.30 per square foot it puts a sacrificial film between the sun and the binder.

The interval is two to four years. More frequent sealing adds cost without benefit and can build a film that cracks from its own thickness; less frequent sealing lets the surface oxidise past the point where a coat bonds well.

Our [how often to seal a driveway](https://drivewaysealinglab.com/how-often-seal-driveway/) guide sets out how to judge the interval from the surface rather than the calendar.

## Target three: keep water moving

| Check | What good looks like | What to fix |
| --- | --- | --- |
| Surface grade | Water sheds toward the street or a drain | Re-grade low spots |
| Ponding | Gone within 24 hours of rain | Channel drain or reslope |
| Edges | Soil or turf level with the pavement | Add and compact shoulder material |
| Cracks | Filled before they reach 1/4 inch | Fill at $2-$5 per linear ft |
| Downspouts | Discharge well away from pavement | Extend or redirect |
| Gutters | Clean and flowing | Clear debris |

Water is the accelerant in almost every alligator case. A driveway that sheds water ages noticeably more slowly than one that ponds, even with identical traffic, because the base underneath stays dry and keeps its strength.

## What sealing can and cannot do

Sealing slows oxidation and reduces surface water entry. That is a real contribution to prevention.

It does not add structural capacity. A driveway with a base too thin for the loads it carries will fatigue-crack no matter how faithfully it is sealed.

It also does not fix cracks that already exist. Sealer applied over an open crack splits along the crack line within a season, and the split edge lets water in.

So sealing belongs in the prevention plan, after drainage and repairs, not instead of them. The order matters as much as the product: a coat applied before the drainage is corrected is protecting pavement that is still being undermined from below, and the money is spent twice when the base is eventually fixed.

## A prevention routine that fits a normal year

1. Walk the driveway after the spring thaw and mark new cracks with chalk.
2. Fill any crack wider than a quarter inch at $2 to $5 per linear foot.
3. Check drainage; note any water still standing a day after rain.
4. Repair edge breakdown before it reaches the pavement.
5. Seal every two to four years at $0.15 to $0.30 per square foot.
6. Keep heavy vehicles off the driveway if the base was built for cars.

That routine costs roughly $80 to $180 a year on a 600 square foot driveway, depending on how the cycles fall. An overlay at $3 to $7 per square foot is $1,800 to $4,200, so the maintenance is cheap by comparison.

## If the pattern has already started

Prevention becomes containment once the cracks connect.

Measure the affected area as a share of the driveway. Under a quarter, cut out and patch the failed sections at $3 to $7 per square foot. Above a quarter, an overlay is usually more economical than patching scattered areas.

Do not seal over the pattern. It looks uniform for a season and then re-cracks along the same lines, with failed film along every crack.

Our [alligator cracking repair](https://drivewaysealinglab.com/alligator-cracking-repair/) guide covers the repair decision, and [alligator cracking cost](https://drivewaysealinglab.com/alligator-cracking-cost/) prices each option.

## The one prevention step most people skip

Diagnosing the base before the surface fails.

A driveway that has started to deflect, where water stands in a shallow depression, or where the edge has begun to settle, is telling you the base is losing support. That is the moment to investigate, before the pattern appears.

A base assessment and local repair costs a fraction of an overlay. Waiting until the cracks connect means paying for the overlay anyway, plus the years of sealing that were spent on a surface already failing underneath.