Driveway Sealants - Which products are
best for your asphalt driveway?
by Roy Barnhart for the Handyman Club of America
Sealcoating an asphalt driveway every three years not only will make it look better, it actually will make it last longer. Sealing shields paving from the sun's ultraviolet rays, which can deteriorate the binder and expose the aggregate. Sealcoating also prevents water and ice from getting into the paving and causing it to crumble.
The sealcoating materials and crack-filling products available to do-it-yourselfers are not as good as those available to the trade. However, few tradespeople use the best products available, so you can often still do the job better yourself if you use the right materials — and you'll save up to 65 percent of the cost of professional maintenance.
For most of you, choices will be limited to what's available at your local home center or hardware store. Many larger cities have a distributor of asphalt coating products used by con©tractors. You may be able to purchase these professional-grade sealers and fillers, but remember that contractors buy in bulk. Most pro-grade sealers come in 55-gallon drums, not the 5-gallon buckets you'll find at the home center. If you want to get the top-of-the-line sealer, check with your neighbors about buying enough to seal several driveways at the same time.
Coal tar vs. asphalt
Most consumer-grade driveway sealers are water-based emulsions containing water, clay fillers, latex, polymers, additives and either coal tar (a byproduct of baking coal to make coke) or asphalt (a byproduct of petroleum refining). Some so-called “asphalt” emulsions also contain some coal tar.
Although significant improvements have been made in asphalt-based sealers in recent years — the use of polymers and other additives that increase durability and resistance to oil and gas, for example — coal tar products still are most popular. According to the sealer manufacturers, coal tar sealers are more durable and much more resistant to oil or gasoline pene©tration than asphalt-based sealers because gasoline and oil are both sol©vents for asphalt but not for coal tar.
Asphalt-based sealcoating products are better for air quality because they do not emit high levels of volatile organic compounds (VOCs) like the coal tar-based products do. They also smell better and are less of a skin irritant.
Judging the quality of driveway sealers
Both coal tar and asphalt-based products are available in plain or filled-sealer formulas. Filled sealers contain sand or other solids that fill small cracks and holes.
Comparing the various additives and solids used by different manufacturers is difficult because the formulas are considered proprietary information. The general rule is that the top-quality sealers will have the greatest amount of solids left on the asphalt after the liquids evaporate and cure.
The best way to determine quality is by the length of the warranty. The best-grade sealers typically have a five to six-year warranty. The better-grade sealers are generally warranted for three to four years. Plain sealers will carry a warranty of one to three years. Each manufacturer has its specific prorated warranty, which is usually clearly displayed on the label.
A fourth category of sealer has been developed within the last five years or so. It's best described as airport, racetrack or pavement-grade. This grade of sealer has more durable acrylic polymers and lasts longer than other formulas. Some come with a 10-year warranty.
Cost and coverage
Low-end sealers range from $5 to $8 for a 5-gallon pail that covers about 400 sq.ft. These are usually just a thin coal tar or asphalt-based, paint-like coating. Don't expect them to last more than one season. Unsanded or “plain” sealers (the better grade) with heavier solid content range from $8 to $11; the best-grade filled sealers cost about $12 to $15. Heavy-duty or racetrack-grade sealers sell for around $20 for a 5-gallon bucket.Coverage varies between grades. A 5-gallon bucket of low-end sealer covers around 400 sq.ft. The better and top-grade sealers typically cover 250 to 350 sq.ft., depending on the condition of the driveway.
Sealer manufacturers recommend applying sealer with a wide rubber squeegee for the most uniform coverage. Pictured at left is a combination long-handle broom/squeegee sold at most hardware stores.
It's important to fill cracks and seal expansion joints between asphalt and other surfaces, such as concrete aprons or curbs, to keep water out and prevent erosion of the paving base. Filled sealcoating materials will handle cracks up to 1/8 in. wide.
Hot-applied sealers are best for filling cracks from 1/8 to 1/2 in. wide. Pli-Stix driveway crack and joint filler, made by Dalton Industries, is the only DIY hot-applied product. You press the coiled material into place and heat it with a propane torch (preferably with a flame-spreading tip) or a heat gun until it melts into the crack. Pli-Stix comes in a 1/2-in.-diameter, 30-ft. roll. It can be stretched to fit 1/4-in.-wide cracks or doubled up to fill 1-in. cracks. It also has a lifetime warranty.
Most consumer-grade crack sealers are cold-applied asphalt emulsions with varying concentrations of latex and polymers. They are available in pourable jugs for cracks up to 1/8 in. wide, caulking gun cartridges for 1/2-in.-wide cracks, or as trowelable material for wider ones.
If a manufacturer rates its crack fillers using a good-better-best scale, get the best quality product if you want it to hold up as long as the sealcoating itself.
Sealer manufacturers and asphalt contractors agree that most asphalt driveways only need to be sealed about every three years. The exception would be in extremely harsh regions, such as the South or desert areas, or when the asphalt turns gray. Graying indicates that the surface is oxidizing and loosing the binder that holds the aggregate in the asphalt.
According to sealer manufacturers and engineers at the Asphalt Institute, most driveways do not need filled sealer until they have begun to develop fine cracks. This generally happens after several years. Let new asphalt cure for about a year before sealing, and then use just a plain sealer.
If you do like to seal every year to keep your driveway looking new, use
budget-priced, unsanded or nonfilled sealers. The drawback to sealing every year
is that the sealer can build up and will eventually peel, which also leads to it
tracked indoors. Sealer can permanently stain vinyl flooring even if you remove it promptly. While some brands boast special ingredients to prevent tracking, proper application and curing are key to avoiding problems.
Finally, it's best to repair cracks and holes in the fall and let them cure over the winter. Then, come spring, hose off the driveway thoroughly and apply single coat of sealer. One thin coat of sealer, regardless of the grade, will give you the best results. Multiple coats do not protect any better and actually will cause problems by cracking and peeling.
Patching and leveling
The best repair for really "alligatored" paving is removal and patching. But Gator-Patch by Maintenance Inc. and Gator Pave by SealMaster can stabilize and level badly cracked asphalt without removing it. You apply them like a filled sealer using a pole-mounted squeegee.
You'll mix the latter with water and spread it from a feathered edge to up to 1 in. thick in 1/4-in. layers.