Think before you sink more money into a cracked driveway
Q: Our asphalt driveway has developed cracks and several sunken spots. The driveway was resurfaced just before we purchased the property three years ago. Can this be repaired by simply applying a thicker layer over the surface? Is this a project for a do-it-yourselfer?
A: An asphalt driveway that has been resurfaced several times and is deteriorating overall should probably be removed and a new driveway installed.
The feasibility of restoring the existing driveway depends on the condition of the foundation. Blacktop in and of itself, has very little tensile strength. It derives the greatest portion of its strength from the base or foundation. Herein lies the source of most cracks in blacktop.
The base for many blacktop driveways is crushed gravel. This base is usually applied directly on the soil. Both the base and the soil have to be able to support loads that will be placed on it.
For durability, an asphalt driveway foundation requires solid earth, not mud. A shallow bed at least 12 inches deep should be prepared to hold three layers of materials starting with a sub-base of oversized limestone rock (3 to 4 inches in diameter) tamped down in a compacted layer at least 8 inches thick. An additional finish base is then installed over the sub-base comprised of crushed limestone spread evenly and compacted in a layer approximately 6 inches deep. Four inches of asphalt, installed in two layers are then applied to finish the surface.
Proper drainage away from the driveway is another important factor. An asphalt driveway properly installed can last for 15 to 20 years. Unfortunately, many times shortcuts are taken in the original construction and homeowners suffer with untimely deterioration. You may want to seek a professional opinion on the condition of your driveway and its foundation prior to proceeding with repairs.
If a quality foundation was installed to begin with, an older driveway can often be restored to like-new condition by some relatively inexpensive maintenance steps.
The first step is to give your driveway a thorough inspection. If serious cracking covers 75 percent of the surface, don’t consider resurfacing. The existing driveway should be removed. If the surface remains fairly well intact with a few cracks and some potholes, it is likely that you can repair these yourself. Loose material in potholes or crumbled areas should be dug out to the earth base of the driveway. Weeds growing through the cracks or holes should be pulled out by the roots if possible, and the entire driveway should be swept clean of loose dirt and hosed down. The entire surface should be cleaned with a special asphalt-driveway cleaner or scrubbed with a strong detergent and rinsed thoroughly.
The basic materials needed for blacktop repair are bagged, premixed asphalt patch for filling potholes, badly damaged areas and large cracks; asphalt crack filler for cracks up to ½-inch wide, and surface sealer (called coater by some manufacturers).
When patching, clean out all loose asphalt and gravel. Scrape around the edge of the hole until you have a solid edge. Fill the hole to within 1 inch of the top with asphalt patch mix. Use a 4 x 4 piece of timber to tamp the mixture into the hole. Make sure it’s pressed firmly against the edges. Add additional patch mix so the filled area is about one-half inch above the level of the driveway. Finally, tamp this area flush using the timber.
If the hole you’re filling is deep (3 inches or more), you may need to place a board over the patch and drive your car over it to firmly seat the patching material.
After filling cracks and patching holes, you have to wait a while before sealing. Follow the manufacturer’s directions on recommended timing and specific application instructions. The purpose of sealers and fillers is to prevent moisture from working its way into the asphalt, since it causes most of the damage to asphalt driveways.
In colder climates, the water expands and contracts when it freezes and thaws, breaking up the asphalt. In warmer areas, water can wash away the asphalt base, which leads to low spots or depressions in the driveway’s surface.
If you proceed with repairs be sure the weather conditions are in your favor. Avoid any possibility of rain during the process. Most manufacturers recommend that the temperature be at least 55 degrees. Warmer and less humid conditions will speed drying time.
Asphalt driveway sealers usually come in five-gallon containers, which cover 200 to 300 square feet. Sealer is best applied with a special long-handled brush-squeegee, sold wherever sealer is sold. There are two types available: regular sealer or sealer/filler combination, which has tiny fibers that fill hairline cracks. Remember that a sealer is a preventative coating, not a repair.
Crack filler is available in one-gallon, pourable liquid containers as well as in caulk tubes. The caulk type is neater, but you’ll use more tubes than liquid, making it more expensive overall. Asphalt patch is most often sold in bags weighing about 60 pounds, containing about half a foot of patch material, which is enough to fill a 1 x 2-foot hole to a depth of 3 inches.
For a complete resurfacing, and a more permanent surface repair, hot-mix patch, fillers and sealers are used. The hot-mix materials and equipment, however, are not available to the do-it-yourselfer. For that reason, the repairs you make with cold patch may need to done again in the future. If you choose to have hot-mix repairs done, contact an asphalt paving contractor.
Send e-mail to copleysd@copleynews.com or write to Here’s How, Copley News Service, P.O. Box 120190, San Diego, CA 92112-0190. Only questions of general interest can be answered in the column.
