Routing Cracks Before You Seal Them

Routing opens a narrow, working crack into a reservoir so sealant can sit below the surface and move. It is the wrong tool on alligator maps, hairline crazing, and crumbling edges.

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What routing is for

A router or crack saw follows a single crack and cuts a uniform channel. The sealant then has depth and sidewalls to bond to, instead of sitting as a cap on a dirty line. That helps on long, working cracks that open and close with temperature, including many joints that run across or along a driveway. It is a maintenance step for a pavement that still has strength. It is not a way to draw a grid through alligator cracking. Those cracks are the surface expression of a failed section. Routing them creates more loose pieces and a channel system full of filler that will shove. It is also the wrong tool for a pothole, which needs a square patch. Sealcoat over a routed crack does not replace the sealant. The sealant is the waterproofing for that joint.

How a homeowner should think about the cut

Routing throws dust and leaves a sharp channel that must be cleaned before any sealant goes in. Dust left in the reservoir is a bond breaker. The channel dimensions should match the sealant maker's recommendation, not the deepest cut the machine can make. A very wide, deep slot in a thin residential driveway can cut through the mat and weaken the edge of the crack. If you do not have the machine or the cleanup, a hand-poured filler in a cleaned, narrow crack may be the better small-job choice, and a contractor who routs regularly is the better choice for long joints. Call for utility locates if a crack could be over a shallow line you do not want to nick. A measuring wheel can estimate linear feet. It is not a survey. Do not route in the rain and fill a wet channel.

When to skip routing and change the repair

Skip routing when the crack is a tight hairline that is not taking water, when the pavement is a spiderweb of load cracks, when the edge is raveling into the crack, or when the 'crack' is actually a joint between asphalt and a structure that needs a different seal. In those cases, clean and monitor, patch, or rebuild. If you route and the sidewalls crumble, the mat is too weak for this maintenance and the area should be cut out. Estimate replacement tons at AsphaltTons.com for that area and thickness, and confirm the plant's density and price. After a successful route-and-seal, tool the sealant low so plows do not peel it. Keep traffic off for the cure the product states. A routed joint that is filled flush and stays closed is doing its job even if you can still see the line.

A practical sequence

Route only single, working cracks in pavement that is still sound.
Match the channel to the sealant instructions and clean the dust out.
Do not route alligator cracking, hairline crazing, or potholes.
Fill, tool the sealant low, and keep traffic off for the stated cure.

The mistake to skip

Routing a grid through alligator cracking and filling the grid with sealant.

Questions people ask

Does every crack need to be routed?

No. Many narrow, stable cracks only need cleaning and the right filler. Routing is for joints that need a reservoir.

Can I route with an angle grinder?

A grinder is hard to control in a wandering crack and can widen the damage. A proper crack saw or a hand method is safer on a driveway.

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