HOME IMPROVEMENT : Sealer Paves the Way for Protecting the Driveway

Asphalt is a tough blend of crushed rock, sand and petroleum products, but it’s not invulnerable. The surface of an asphalt driveway deteriorates if it isn’t treated every so often. Yet, “nobody much thinks about maintenance of asphalt,” says Steve Cashdollar of Preferred Paving Co. in Fullerton.

The first and most effective step in maintaining your drive is to seal coat it every two to four years. A slurry seal coating will do for an asphalt what varnish does for wood, says Bruce Alston, sales manager at Oliver-Mahon Asphalt in Costa Mesa.

Asphalt may seem impervious to damage, but when asphalt starts to look gray, it is beginning to oxidize. The sun evaporates the surface oil that helps bind it, and crankcase oil and gasoline dripping from cars contribute to the deterioration. Finally, the asphalt starts raveling--the small bits of sand or “fines” fall out, leaving a coarsening surface that begins to crumble.

The seal coat acts as a binder and restores the fines to the surface.

Because residential drives are so small, usually less than 1,000 square feet, the larger asphalt companies rarely bother to bid on paving, repair or seal coating, Alston says.

If they do tackle a job, they often have minimum charges of $300 to $1,500. More often, maintenance and repair is left to mom-and-pop operations.

And while you can hire a small company to seal your drive, it is not a difficult or expensive process to do yourself. A five-gallon can of sealer available for less than $50 will cover about 400 square feet of driveway.

Apply the sealer in cool, dry weather. Scrub off any oil and grease using water and detergent and leave the surface damp. Fill the smaller cracks, those only an inch or so in diameter, with a rubberized crack filler available at home improvement stores. For larger patches, hot asphalt, asphalt compound or one of the other patching materials available can be introduced into the crack and tamped down.

Filling the cracks may take three or four applications because the filling material will shrink, Cashdollar says. Waiting a week between applications will give the material time to shrink.

Once the cracks are patched, apply the sealer with a squeegee or brush according to the sealant manufacturer’s directions.

Under some circumstances, your asphalt drive may give up the ghost no matter how well you maintain the surface. Earthquakes occasionally cause cracks. More frequently, poor paving techniques used in the original construction lead to cracking, says Cashdollar.

Builders don’t put in the asphalt until the home is nearly done and sometimes shave costs by paring the three or four desirable inches of asphalt to just two inches.

“A layer of two inches of asphalt is OK if there’s proper drainage, and a car goes straight on top of it,” Cashdollar says. “It won’t sustain a motor home, which weighs three to five times more than a car.”

The weight of a motor home will strain even a properly constructed asphalt drive not built with a motor home in mind. Asphalt structurally can’t handle as much weight as concrete.

For a residential drive, “The nice thing about asphalt is, it has a little more give to it” than concrete, Alston says. “You can also get a lot of motion without the surface failing. That’s probably the only plus for asphalt.”

A correctly paved asphalt drive will also have a subgrade consisting of a three- to four-inch aggregate base that has been well compacted and pitched for drainage. If the paving contractor doesn’t give adequate attention to compacting, cracking eventually occurs. In a very substandard paving job, the paver lays the asphalt on the native soil, with no subgrade.

A crack does not necessarily mean poor subgrade; it simply means the earth has moved, Cashdollar says. But over time, a crack in the asphalt can result in an increasing amount of damage.

“Water is the No. 1 destroyer of asphalt,” Alston says.

Sandy soil makes good subgrade because water percolates through the sand, but the clay soil found in many areas of Orange County acts as a sponge rather than a conduit. Once the water has penetrated the subgrade, it is virtually impossible to dry out under the surface, Cashdollar says.

In an extreme case, if the subgrade gets thoroughly wet, it starts “pumping.” That is, an automobile tire will sink into the asphalt surface, and on either side of the tire the asphalt will lift, break and crumble.

If there’s pumping, the wet base must be removed by digging down till the earth isn’t wet. If the subgrade is clay, the paver sometimes reinforces the asphalt with wire mesh or steel, says Al Giese, president of A&Y; Asphalt Contracting in Corona.

Tree roots can crack the asphalt surface and let the water in. Ficus roots, for example, run along the surface of the ground looking for water; they are easily capable of pushing up the asphalt until it cracks. In such a case the root must be cut back, and the section of asphalt replaced, Cashdollar says.

Consider hiring an arborist to prune these roots to prevent the problem from occurring again. Improperly pruned, a tree root can grow back, but there might be five roots where there had been only one.

The landscape specialist can also put in a polyethylene root barrier so the tree’s roots will grow downward instead of out, Cashdollar says.

In recent years, asphalt has become almost obsolete in new projects, says Alston. Concrete is now priced competitively with asphalt for jobs the size of an average driveway. A driveway that cost $1,800 to do in asphalt might cost $1,900 in concrete. Removing and replacing an asphalt drive will cost about $3 a square foot.

If you’re planning to sell your home, apply a coat of sealer to the asphalt. The home’s curb appeal will improve, Cashdollar notes.