DESIGN SCHOOL Henri de Marne

Some Simple Guidelines and Tips for Sealing a Driveway

Q: Here's my dilemma: My asphalt driveway was installed in 1998 and has at least a 4-inch base. I have applied the same type of sealer throughout the years since then and have never had a problem.

This summer, all the layers of sealer seem to be coming up in pebble-sized clumps. I can see the base and it looks good. I obviously cannot apply another layer of sealer in its current condition. Although this past winter in western Pennsylvania was mild, the two winters prior had a lot of ice and freezing and thawing.

Do you think this has something to do with it? What is the best way to remove the layers of sealer and start over? It's a fairly long driveway -- I usually need about 50 gallons of sealer each time.

I'm also considering trying to use a power-washer to try and break up the remaining sealer. Do you have any other ideas to causes or solutions for removal? I've attached a few pictures for your review. Thanks.

A: Here is the answer I gave a reader of my newspaper column some time ago, as copied from my book: "About the House with Henri de Marne," with some editing and additions:

"The adhesion failure of a seal coat on an asphalt driveway may be caused by a number of factors. Since you haven't given me enough details, (such as how frequently did you apply new coats of sealer?) I'll run through the gamut, hoping that you will see your problem.

"If the sealer was applied too soon after the installation of the driveway, before all the oils have had a chance to evaporate, the oils will prevent proper adhesion. A newly laid asphalt driveway needs several years for the oils to dissipate. You can tell when it is time to put on a sealer when the driveway turns a light gray and feels 'dry.'



"Sealer failure can also occur if the driveway was not thoroughly cleaned before applying it. All kinds of pollutants may be imbedded in the asphalt, and need to be removed. A power washer used with care so as not to damage the surface is a good way to clean the driveway.

'Applying the original sealer in too cool weather or too thickly can also affect adhesion, as can a pitted or cracked surface.



"Flaking or peeling can also occur if the original coat of sealer has not aged enough before applying another one. This may take several years."

You may have applied new coats of sealer too often. The sealer needs to wear out almost completely before a new coat is applied. Your problem may be due to the multiple coats becoming too thick. Remember the saying about the straw that broke the camel's back.

In addition, preparation is absolutely essential. Any oil spots must be removed by sprinkling TSP-PF crystals on them, followed by a light sprinkling of hot water. Gently brush the resulting mixture to allow it to soak into the oil spots and let it stand for 20 to 30 minutes. Briskly scrub the mixture with a stiff brush and rinse with your garden hose. Be aware that TSP-PF is injurious to vegetation.

A pressure-washer is a good tool to use to remove all the loose or nearly loose sealant, but do not use too strong a jet; it would damage the asphalt driveway. Scraping of remnants may be required.

Once you have succeeded in removing all of the sealer coats, let the driveway stand alone for a year or two. Remember that the right kind of sealer is OK, but sealers are not necessarily essential. Many driveways, as well as asphalt roads, are never sealed and do quite well.

The longest-lasting sealer to use is a coal tar sealer, but this type of sealer has its own environmental and health problems, particularly for the applicators. Next in line are acrylic sealers, which are much more environmentally friendly than coal tar sealers, but do not last as long.

(For editorial questions, please contact Clint Hooker at chooker@amuniversal.com.)

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