Filling cracks takes a short shopping list and an order of work that matters more than the product. Here is the kit to lay out first, which filler suits which crack and the steps that keep the repair from failing.
In This Article
The kit to lay out before you start
- Wire brush and a stiff pick or old screwdriver to rake dirt and crumbs out of each crack.
- Leaf blower or shop vacuum to clear the dust the brush loosens.
- Filler. A pourable or tube-applied cold filler suits most home jobs. Pick one labelled for asphalt cracks and check its temperature limits.
- Caulking gun or pour-spout bottle, depending on the product.
- Putty knife or a small squeegee to level the surface of the filler.
- Dry sand for blotting the surface, if the label allows it.
- Backer rod or coarse sand for deep, wide cracks, so the filler does not sink out of sight.
- Gloves, safety glasses and a knee pad. Filler is messy, and the work is low to the ground.
Hot-applied rubberized filler needs a melter and a high working temperature. Leave that type to crews with the equipment.
Match the material to the crack
| Crack | How to recognize it | What to use |
|---|---|---|
| Hairline | As fine as a strand of hair, and a fingernail will not enter it | Often left for the sealer to cover |
| Narrow to medium | A fingernail slips in, up to roughly a pencil's width | Cold filler, applied in one steady pass |
| Wide | A finger's width or more, with clean edges | Backer rod or sand to set the depth, then filler in layers, as the label directs |
| Broken or sunken edges | The pavement on either side has crumbled or dropped | A patch job, which is not a filling job |
Widths are a rule of thumb. The filler's label sets its own limits, so follow it.
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The order that works, step by step
- Pick a dry, mild spell. Fillers have minimum temperatures, and damp cracks will not bond. In Southern Ontario, spring cracks open after frost, so wait until the pavement has dried out.
- Clean each crack down to solid edges. Rake out dirt and crumbs, pull roots and weeds, then blow or vacuum the dust away.
- Let it dry completely. A few hours of sun after a rain is not always enough for deep cracks.
- Set the depth in wide cracks. Press in backer rod or pour in coarse sand, and leave room for the filler.
- Fill from the bottom up. Move slowly along the crack so air does not get trapped, and stop as the label directs.
- Level the surface. Draw a putty knife or squeegee along the crack so no ridge remains. A ridge catches snowplow blades and wears off.
- Let it cure. Keep feet and wheels off it, and wait as long as the label says before sealing. Cool or humid weather stretches that time.
Checking the repair before you seal
Give the filler a day or two beyond the label's minimum if the weather has been cool, then walk the driveway and look at each crack from a low angle. A good repair sits level with the pavement, with no gap along either edge and no soft, tacky centre.
Fillers often shrink a little as they cure. If a line has dipped, top it up in a second thin pass and let that cure too. Press a fingertip lightly into a hidden spot to test whether it has firmed up. If it still feels wet or sticky, the sealer is not ready to go over it, and a few extra dry days cost far less than lifting a failed coat.
Mistakes that waste the repair
- Filling over dirt or damp. The filler sits on top and peels out.
- Using the wrong material. Household caulk, mortar and concrete patching mix do not flex with asphalt through a freeze-thaw winter.
- Overfilling into a wide ribbon. It looks untidy and gets scuffed by tyres.
- Sealing too soon. Sealer over uncured filler can stay soft or pull away.
- Ignoring the cause. A crack that keeps reopening at the edge of a lawn or beside a tree may have a cause that filler cannot cure. Read why crack filling before sealing is essential for how cracks form.
When it is bigger than a filling job
Call in help when cracks form a web, when the surface feels spongy or sits lower than its neighbours, or when a crack is wide enough that you can see base material. Those are signs of a problem beneath the surface, and filler only hides it.
D&D Home Services includes driveway sealing among its services, and its quotes are free and confirmed in writing before work begins. Ask for the crack treatment to be listed as its own line, so you can see what will be filled and how.
Key Takeaways
- Lay out a wire brush, pick, blower, filler, applicator, putty knife and safety gear before you start.
- Hairline cracks are often left for the sealer, and cracks a fingernail can enter need filler, with backer rod or sand in wide ones.
- Clean to solid edges, dry the crack fully, fill from the bottom up, level the surface and let it cure before sealing.
- Webs of cracks, spongy spots and sunken edges point to a base problem that filler cannot fix.
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