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Washington Post

Do I really need to seal my driveway?

Q: Do I really need to seal my driveway, or is that a racket? And can I do it myself? A: There is considerable debate about whether it's truly necessary to seal asphalt or concrete driveways, but there is also general agreement about the benefits of doing it. Both concrete and asphalt are mixtures of sand, gravel and a binder that holds everything together. In concrete, the glue is Portland cement. In asphalt, it's petroleum-based oil. Both types of paving, if installed correctly with drainage factored in, can last for decades as-is. But both types can also absorb — or be broken down by — spills. Acids and salt are big enemies for concrete; dripping oil from a vehicle can break down asphalt. Ultraviolet rays and heat from the sun can bleach colored concrete and degrade asphalt by making it more brittle and prone to cracking under pressure. And water is one of the worst foes for both types of paving. Where temperatures dip below freezing in the winter, the surfaces can crack when water seeps in and expands. Sealers help keep water from penetrating into the paving. Some have other benefits, such as blocking UV or protecting against stains. And all sealers help a driveway look like it's well cared for. For concrete, you can use a penetrating sealer, which seeps into the minute pores that were left when water in the original concrete mixture evaporated; or a topical sealer, which sits on the surface. For a driveway, the best choice is generally a penetrating sealer with siloxane and/or silane, such as Foundation Armor SX5000. It won't change the look of the concrete or make it more slippery, but it should block water and salt — and all of the problems they cause — for seven to 10 years before it needs to be reapplied. The manufacturer warns, though, that because it isn't a surface coating, it won't block stains. Nor does it resist spilled brake fluid, gasoline or many other solvents. To get more protection against stains (though still not against brake fluid, gasoline and solvents), you would need a surface sealer, such as Foundation Armor AR350, which would give the surface more of a wet look. By darkening the color, it would also help bring out any color added to the concrete, and it would protect against UV, which can cause colorants to fade. You could also mix in color to change the look of your driveway; Armor Foundation sells color packs that result in an opaque coating, like paint. But a surface coating would make the concrete slippery when it is wet, so for a driveway, you'd probably want to use an anti-slip additive or buy a sealer with that feature built in. Also be aware that a surface sealer typically doesn't last very long. You'd need to commit to ongoing maintenance, and you would need to reapply it in one to three years. If your driveway is asphalt, you'll probably want a water-based asphalt sealer. (Coal tar sealers are still sold in parts of the country, but some states have banned them because of concerns about toxic substances in the runoff.) The most challenging part isn't applying the sealer, usually with a squeegee; it's cleaning the surface and filling all the cracks. Pricier sealers include fine sand and other aggregates to help fill tiny cracks (wider cracks and any holes still need to be patched beforehand) and they are likely to last longer than their less expensive counterparts. Black Jack Drive-Maxx, sold at Lowe's and Ace Hardware, comes in formulas labeled 200, 400, 500, 700 and 1000; the 200 type is expected to last two years — probably good only if you're about to put your house on the market, given that all the preparation steps are the same. The 1000 sealer is expected to last 10 years. To decide whether you should seal your driveway yourself, read the technical data sheet, often referred to as the TDS, for the sealer and make sure the steps seem like ones you're able to follow precisely. Details about surface preparation, the application process, the weather and even the time of day really matter, and they vary by product. For example, with its topical sealer, Armor says to work after 5 p.m., when the temperature is dropping and the driveway isn't likely to be in direct sun. For Black Jack Drive-Maxx 1000 asphalt sealer, though, you should work when the temperature is rising. With concrete sealers especially, apply the product in a small test area before you coat the whole driveway. That way you can avoid unexpected problems, which can occur if an earlier sealer is incompatible with what you are applying, or if the driveway isn't clean and dry — or damp, the requirement for some asphalt sealers. Calling a pro might be especially helpful if you don't know what care your driveway has received in the past. Family Handyman has a good step-by-step guide for installing asphalt sealer, including tips about the main ways people mess up, such as by trying to stir a bucket of thick, gooey sealer with a stick instead of with a paddle powered by a drill. The guide author's answer to the question of whether asphalt sealers are really necessary? 'It's true that driveway sealer can't replace the liquid asphalt (oil/tar) that oxidizes and bakes out of the mixture from heat and sun exposure. But a high-quality sealer can dramatically reduce future heat and UV damage. Plus, it seals the pores to prevent aggregate breakup damage caused by water penetration, freeze/thaw cycles and chemicals. So it really does extend the life of your driveway.' Have a problem in your home? Send questions to localliving@ Put 'How To' in the subject line, tell us where you live and try to include a photo.