Why do cracks in my driveway keep reappearing, and how do I fix them?
Q: As spring approaches, I will, once again, seal my asphalt driveway. I have repaired the cracks many times, using different media. Nothing seems to work. What do professionals do so they don’t have to repeat this step each year?
A: Professionals are likely to use hot-applied crack and joint filler, which can last up to 10 years, far better than a cold patch, which might last only one year, according to Pavemade, which makes both types of filler. The heated option flows into cracks and voids better, and once it cures, the material remains stretchy, allowing it to stay bonded to both sides of a crack as temperatures fluctuate.
You can buy hot-applied filler at a home center: Home Depot sells a 50-poound box of Crack-Rite’s hot pour direct fire joint sealer for $63.43), and Lowe’s sells a 30-pound box of Crafco’s flex-a-fill for $43.68. But the instructions and safety warnings make it clear why this type of filler is marketed to pros, not homeowners. You need to heat the material before it is applied, and you need a way to keep it warm while it bonds with the crack. Pros usually use a propane-heated kettle and a propane blowtorch. For a homeowner looking to patch cracks just once every 10 years, the price of the equipment is one obstacle: The smallest kettle (10 gallons), mounted on a push cart instead of trailer that needs to be pulled by a pickup truck, could cost $1,000 or more. (Home Depot sells a Crafco model for $1,800.)
There are also significant safety precautions and precise application conditions involved. The hot asphalt will cause severe burns if it gets on skin. The vapors might contain hydrogen sulfide, which can be lethal if inhaled in a concentrated amount. The filler needs to be at least 370 degrees when it is applied, but if it gets just 20 degrees hotter, it can gel within the kettle.
All of this adds up to make hot-applied crack and joint filler a material best left to pros.
But there is a way to get the benefits of a melt-in filler in a more homeowner-friendly product. Dalton Enterprises, which makes a full range of pavement products, says its Latex-ite Pli-Stix permanent blacktop joint and crack filler, which comes in a rope format, is the same material that pros apply on roads, except that you melt it in place with a propane torch after you push it into cracks. It bonds like a hot-applied filler but saves you from having to handle that hot material. A 30-foot roll of medium-width, for patching cracks ½- to 1-inch wide, is $13.98 at Home Depot. Pli-Stix also comes in small size, with rope ¼-inch wide.
To use the rope, first prepare your driveway by cleaning out the cracks. You can use a flat-tip screwdriver and a whisk broom, although a leaf blower or compressed air might be more effective. (Be sure to wear eye protection.) Washing the driveway with a degreasing detergent can also help, but rinse thoroughly and wait for the pavement to dry completely before you fill the cracks. Trapping water would defeat the purpose of filling the cracks to seal them.
Unroll the rope, but don’t take off its plastic wrapping, which will melt away when you heat the rope. Push the rope into a crack with the screwdriver. If you get to a section where the crack is narrower than the rope, stretch the rope to make it skinnier, or trim it with a razor blade. If a crack is deeper than the rope is wide, fill the bottom of the crack with sand before applying the rope. Use the screwdriver tip to push the rope down so it is slightly below the surface of the pavement. Leaving the rope in the sunshine for a bit will soften the material and help it conform to the shape of the crack.
When the rope is in place, light your torch and melt the rope, which should take 20 to 30 seconds. To keep the filler from catching on fire yet still get it hot enough to melt, the Family Handyman website recommends working in sections about a foot long. Heat one section, move on to the next section, then go back and reheat the first section until the rope shape collapses and the top of the filler is flat and connected to both sides of the crack. Continue in this stair-step way for the whole crack.
The Latex-ite instructions recommend using a handheld Bernzomatic torch. But it’s really helpful to get an extension wand so you don’t have to fight the tendency of a propane cylinder to snuff out when tipped upside down. Plus, after all the on-your-knees work of cleaning and filling the cracks, it’s nice to be able to do the heating step standing up. Latex-ite’s 32-inch CSX 900 torch extender, which the company sells on its website for $59.99, keeps you and the cylinder upright but directs the flame down, into the crack.
The rope sets up in about 20 minutes, but wait 24 hours before sealing the pavement.