The key to success is in the prep

By Jeff Winke

Effective asphalt sealcoating starts with the preparation. As one contractor said… with sealcoating it is 95% preparation and 5% actual sealing. It is as Benjamin Franklin astutely said: “By failing to prepare, you are preparing to fail.”

Prep work involves a lot of surface cleaning.

“Critical to the success of a sealcoat application is the clean removal of all vegetation and debris from the pavement surface,” stated Chris M. Vacca, senior marketing manager with Crafco, Inc., Chandler, Arizona. “Clean the surface thoroughly to remove all foreign debris, such as dirt, gravel, silt, etc. Use an air blower or flush with water. If there is embedded dirt or silt, use a steel bristle hand broom to remove. When removing dirt and debris from site be careful not to upset the existing landscaping. And do not pile dirt and debris onto grassy areas along the paved asphalt.

“Oil spots must be addressed. If left untreated, the sealer will not adhere and will delaminate. In addition, any untreated oil spots can potentially absorb into the sealer emulsion and impede the sealer’s ability to cure. The end result is a sealer that remains soft — tracking onto sidewalks and interior spaces. Once the oil spot is conditioned, then apply the oil spot primer. Follow manufacturer’s application instructions for primer. Primer can be brushed or sprayed on. Make sure to cover the oil spot and two inches of the surrounding area as well.”

Vacca also said: “Crack sealing should be completed prior to any sealcoat application. If cracks are left unattended, water can penetrate to the base soaking and swelling the limestone thus destroying their strength and load bearing capabilities. It is evidenced by “alligator” cracking, sunken areas, and eventually potholes. Cracks at least 1/8” or wider should be treated with a least a cold pour sealant which will seal the cracks for a year or so. For a longer-term repair, hot-pour crack sealant should be used. Hot-pour crack sealant remains flexible for a longer period of time and if used the crack repair can remain effective as long as three to seven years.”

Sealcoat bonding problems appear to be an issue if the paved surface has not been properly prepared.

“Over the years, I have concluded that the majority of sealcoating failures such as premature wear, flaking, peeling, etc., happen due to the bonding problems of the sealcoating to the pavement surface,” said Girish C. Dubey, president, STAR, Inc., Columbus, Ohio. “For the proper bonding of sealcoating, it is essential that the surface be cleaned as thoroughly as possible to remove dirt and debris. The adage that ‘a coating is as good as the surface that it is applied on’ holds true for all coatings. If the surface is not clean the coating will not bond and with time and usage it will flake or peel off. The extent of cleaning of the pavement will depend upon its condition, simple air blowing or more involved scraping, wire brushing, blowing or pressure washing.”

Sealcoating manufacturers are meticulous in detailing the aspects of material and surface preparation prior to sealcoating, and urge the applicators to comply with them. Still it is not always possible to cover all the bases, considering the myriad of pavement types, age and the condition.

“Thoroughly cleaning of the surface that is to be sealed along with repairs of the asphalt surface structure and crack filling of the longitudinal and latitudinal cracks is essential before beginning sealcoating,” stated Robb Archie, president of U.S. Seal International, Inc., Reno, Nevada. “Additionally, you need to apply oil spot primer on the petroleum saturated areas.”

Proper preparation is only part of the sealcoating equation.

“To me, application of the sealcoating is equally important to preparation,” stated Brent Kilbarger, president of Star Seal of Ohio, Columbus, Ohio. “Prep work is important to adhesion and longevity, however the proper sealer mix, how it is applied and when it is applied is very important. The proper air and ground temp, coverage rate, proper spray equipment and proper amount of time to cure is all very important to making a great job last for years of service.”

Kilbarger described the best conditions as a precursor to starting the job: “Make sure the weather will not be too hot, too cold or too wet for the three to five days during and around the time that the job is scheduled to be done. Making sure sprinkler systems are shut off, lawn service/treatment are put on hold, traffic is redirected (both car and foot) for the amount of time needed to perform the job.”

The equipment needed for preparing a site for sealcoating can vary.

“All asphalt surfaces are not the same, and different equipment can be needed for prepping different lots,” Kilbarger said. “Older asphalt with a deep profile may need a heavy rotary broom to clean out the pours of the surface. A newer asphalt surface may have a smother profile and only require a good blowing. If the surface has tree sap, salt residue or heavy pollen it may require power washing for proper adhesion.”

For most, removing vegetation from the edges of the asphalt surface and from the cracks can be accomplished via the use of a mechanical wire wheel.
Vacca said, “Wheeled blowers are essential to removing loose debris. For driveways and small commercial jobs, 6-HP blowers are good, while 9-HP blowers are useful for medium to large jobs, and 13-HP and larger are necessary for the large jobs (10,000 square yards and up).

“For bigger jobs or for extremely dirty surfaces, mechanical wire brooms or sweepers may be necessary. Other typical equipment may include weed trimmers, herbicides, torches, and backpack blowers.”

There are downsides to projects where the pavement surface is ill-prepared.

“The sealer can discolor, non-adhesion to the surface can occur, performance can be impaired, and longevity can be greatly shortened,” reported Dubey. “Before applying, the paved surface needs to be free from surface defects cracks, surface alligatoring, patching and untreated oils spots. Remember, asphalt sealcoatings are not repair products; they are coatings to protect and preserve the paved surface.”

Jeff Winke is a business and construction writer based in Milwaukee, Wisconsin. He can be reached through