A “blacktop” driveway can last for decades, driven over tens of thousands of times, with car wheels following the same paths without issue. It can endure weather extremes that raise the temperature of its pitch-black surface as high as 150 degrees F on a sunny summer day, and it can withstand assaults by snowplows, ice choppers, and road salts in winter. If fissures form, they can be filled to keep water from undermining the gravel base below. And when the asphalt layer begins to degrade—before it becomes completely rutted and crumbling—it can be replaced to upgrade a home’s curb appeal, make comings and goings easier and safer, and provide a smooth surface for everything from basketball to hopscotch—without the need for a full-scale driveway overhaul.
Out with the old, in with the new
To repave an asphalt driveway, that’s deteriorated beyond repair, a contractor will come in with a compact loader, or “Bobcat”; lift off the old asphalt; and dump it into a truck parked on the street to be carted away and recycled. The contractor will top off the aggregate subbase of crushed stone, rake it flat, pitch it so water drains away from the house with a 2 percent cross-slope, and then compact it using a steel-wheeled roller and a vibrating compactor. The next day, a load of hot asphalt, typically about 300°F, will be laid using an adjustable-width paving machine, and compressed and smoothed with a steel-wheeled roller and vibrating plate compactor. Depending on the thickness of the asphalt (a judgment call based largely on the thickness of the base course), you may need two layers
This type of paving is a combination of liquid binder—asphalt, a by-product of crude oil refining—and stone aggregate, sometimes with additives that improve its strength, flexibility, and water resistance. “While concrete is king in most of the country, it can crack under the strains of freeze-thaw cycles, so asphalt is a better choice in cold climates,” says TOH mason Mark McCullough. Not a fan of asphalt’s monolithic black surface? You can imitate the look of early driveways— dirt paths often topped with loose stone or crushed shells—with an asphalt driveway that has a final layer of fine gravel, and you can dress up the edges and entry aprons with granite cobblestones.
Your new driveway may cost $3,000 to $7,000 or more. And, in most cases, there’s no way to repair a botched installation; it could be with you for decades. To help you avoid costly mistakes, we’ve put together expert advice on what to look for in a job well done.
Asphalt at a Glance
- Lasts 15–20 years with regular sealing
- Flexible enough to accommodate freeze-thaw cycles without cracking
- Top layers can be removed and replaced without the need for a from-scratch installation
- Provides a good recreational surface for basketball and more
- Stands up to snowplows and blowers; not affected by ice-melt salts
- Fissures and divots can be filled
- Thanks to its dark color, it heats up in the sun, melting winter snow and ice
- Expect to pay about $7 to $12 per square foot installed
Anatomy of an Asphalt Driveway
Blacktop is a combination of liquid asphalt and small-stone aggregate—sometimes with additives for strength, flexibility, and water resistance. Whether you’re replacing asphalt or installing it for the first time, it pays to understand what goes into a proper installation.
A) Subgrade: For a new driveway installation, the site should be excavated deep enough to match the thickness of the driveway’s components—we’re using 12 inches here, but they can vary depending on local soil conditions—so the finished surface will align with the lawn, walkways, garage entrance, and so forth, and then the soil gets compacted. For asphalt replacements, though, the subgrade typically doesn’t need any work.
B) Subbase: This should be 8 inches of crushed stone, which is a product that has been fractured so it has angular edges that interlock under compression. The best option is aggregate base course, also known as“crusher run,” a mix of stone of every size from about 3/8 inch down to stone dust, so it knits together extremely well. “The idea is to compact it so well that it’s watertight,” Mark says.
C) Binder course of asphalt: Depending on the depth of the aggregate base—every additional 3 inches of aggregate generally means 1 inch less of asphalt—the asphalt is ideally put down in two layers. The first is a binder course, which contains 2½ inches of 5/8-inch aggregate. The binder course gets flattened and compressed with a steel roller and a vibrating plate compactor where the roller won’t go. It is then raked to give it a textured finish that will provide good adhesion with the next course.
D) Finish course of asphalt: The surface course, or topcoat, can be installed immediately, but if there will be construction vehicles using the driveway during a large-scale renovation, it’s common to wait until any such home-improvement project is complete. This 1 1/2-inch layer contains 3/8-inch aggregate. It gets flattened and compressed with a steel roller and a vibrating plate compactor where the roller won’t go, and the edges get compacted using specialized hand tools for a flat, smooth, watertight finish.
Asphalt Driveway Enhancements
Yes, you can dress up asphalt, whether you’re starting fresh or want to enhance what you have.
Tips for Hiring a Paving Contractor
Here are the steps Mark recommends taking when looking for a good paving contractor
Go to the source
Don’t rely on the Internet to find contractors. Visit a local, independent supply yard for asphalt (or whatever paving material you’re installing), and ask at the desk who the best residential contractors are. “They know who’s always got jobs, who’s keeping a big crew of experienced guys employed, who’s reliable about paying their bills.”
Get the facts
“I remember when you could get three bids, all the prices would be similar, they’d all be serious contractors, and you could safely select the low bidder. Now I see people get into trouble with the wrong contractor on a weekly basis.”—TOH Mason, Mark McCullough
When you meet the contractors, they should be willing to take the time to talk through their process, explain in detail what they’ll use for a base course and how thick it will be, tell you whether they’ll use two courses of asphalt, and so on. And a contractor should be wearing boots, driving a truck, and have strong, calloused hands. “If he shows up in a Cadillac and dress shoes, this is not your guy.”
Talk to clients
Ask for some recent customers—some with just-completed projects and some that are a few years old—and try to meet them in person to ask about working with the contractor and whether they would do so again, while checking out the work firsthand.
Asphalt Driveway Maintenance
Asphalt needs a little TLC as time goes by, but one of its pluses is that it can be patched if needed
Sealing
Asphalt needs to be seal-coated, Mark says. Not right after it’s installed, but within five years or so, the liquid asphalt gets depleted by the elements. “Once it goes from black to gray, it’s time to seal.” The DIY products sold at the home center—bituminous or acrylic-based liquids that dry in place—are just as good as what the pros use, Mark adds. “The advantage of hiring it out is that you won’t be covered in asphalt sealer.” The coating protects the asphalt from water and ultraviolet light; it also blackens the graying surface, which many people like. You’ll need to clip away an overhanging grass, clean the surface with a degreaser, paint primer over any stains, cut in the edges with a brush, and mop down the sealer over the rest of the driveway. Plan to throw away the clothes you wear, Mark says, including your gloves.
Fixing fissures
To fix a crack, first clean out any debris, dirt, and plant material. If it’s a hairline crack, use an angle grinder with a masonry bit to widen the crack to the width of the blade. Fill the crack with a melt-in crack filler, which is a cord that you press into the crack and then melt with a propane torch. Cover that with a trowel on asphalt-patching material, and melt that in place with the propane torch.
Filling divots
Again, you have your choice between doing the job yourself—or staying clean and hiring it out. Home centers offer all the supplies you’ll need, and each product has its own specific instructions. In general, to fill a driveway divot, you’ll want to cut even edges around the damaged area using a circular saw fitted with a masonry blade; then lay down a couple of inches of stone and compact it with a hand tamper. Add a wood form if the repair is at the edge of the driveway, then fill the void with a cold asphalt patch—this comes as a ready-to-use bagged product designed to provide a flexible repair. Make sure to overfill the hole by 2 to 3 inches, then compact it with a hand tamper; finally, lay plywood over the top and drive the car over it a few times to compress the patch as much as possible.
Asphalt Driveways Common Problems
By the time defects show themselves in an asphalt driveway, the crew is usually long gone, and there’s not much that can be done to fix the issues. Here are the most common installation mistakes—and how to prevent them.
“Birdbaths”
No driveway is perfectly flat, but the key is to ensure there are no depressions or isolated low spots where water can puddle. A 2 percent cross-slope will ensure that water runs off the driveway.
Ruts or potholes
These problems go much deeper than the pavement. The subbase is almost certainly loosened, dislodged, or undermined by water. To remedy ruts and potholes, a contractor will need to remove and replace the subbase material wherever there is a surface problem, generally about a foot beyond the problem area, and repave it.
Crumbling edges
Aside from potential problems with the quality, thickness, and proper installation of the entire driveway system, crumbling can occur if the edges of the asphalt don’t get compacted well enough. Not only should the crew run the steel-wheeled roller all the way past the edges, and bump the edge from the side using a tamper, lute, or rake (specialty hand tools used for laying asphalt), they might also use a vibrating plate compactor to further compact the edges.
Runoff Remedy: Porous Asphalt
In heavy rains, water can flash flood off a driveway, sometimes picking up oils, bits of tire rubber, and other debris and carrying them to the nearest stream or river. Rather than being compacted into a watertight mass with 7 percent void space, porous asphalt layers have a reduced percentage of small-stone aggregate so they can be compacted with about 20 percent void space. Water moves easily through porous asphalt and into a deep bed of larger rocks with more void space between them, where it pools while it percolates into the ground. There’s no flooding (or erosion), and any debris stays on top, where it’s easily cleaned up.
Along with its environmental benefits, porous asphalt can eliminate the need for a drainage system where a driveway is pitched toward the garage. “And it eliminates puddles and ice by 75 to 100 percent,” says asphalt consultant Bruce Barkevich of the New York Construction Materials Association. Expect to pay about $13 to $18 per square foot installed. To make sure the surface stays permeable, you’ll need to regularly use a leaf blower to remove any sand, soil, pollen, or other debris that collects on the surface that can potentially clog drainage voids in the asphalt.
Some experts recommend against porous asphalt in cold climates, for fear that the water retained in the stone will freeze, expand, and bust up the driveway, but Barkevich says he’s seen no such issues, even in upstate New York. “About the only downside, for some people, is visual,” he adds. “It has a coarser surface than typical asphalt, and you can’t seal it, so it’s going to go gray over time.” A porous asphalt driveway should have these layers:
A) SUBGRADE: Well-drained soil is essential under porous asphalt, so if you have clay soil, for example, it may need to be removed and replaced. The subgrade is not compacted, so it can absorb water that moves through the driveway.
B) GEOTEXTILE (OPTIONAL): This layer of specialty fabric—which allows water but not soil or silt to pass through—helps prevent the stone above it from becoming clogged over time.
C) RESERVOIR COURSE: This layer of “number 57” stone, which is 1 to 11/2 inches in size, can vary widely in depth, depending on soil conditions. Unlike the stone used under standard asphalt, when it’s compacted, about 40 percent void space remains.
D) CHOKER COURSE (OPTIONAL): About 2 inches of 3/4-inch stone (number 78) may be laid on top of the reservoir course. This has 20 percent to 30 percent void space.
E) POROUS ASPHALT: With about 20 percent void space, this driveway paving contains 1/2-inch stone and can be laid in one 4-inch course, or in 21/2-inch binder and 11/2-inch finish courses. It provides a sturdy base for cars and basketballs—but allows water to pass right through.
Landscaping for Your Driveway
The right landscaping can soften the appearance of so much hardscape, reduce the heat-sink effect of paving, and protect your driveway from damage from roots and sap.
- Trees: Much like a tree-lined street, a driveway planted with small- to medium-size trees looks welcoming and leafy. Just make sure to select trees recommended for this location by a local nursery so that the roots won’t undermine your subbase and no sap or berries will drop onto your cars.
- Shrubs: To maintain clear sight lines even as they grow, check plants’ mature size before selecting them to go alongside the driveway, and stay with small specimens for anything near the street, walkways, and patios.
- Perennials: Paving can radiate heat, cars occasionally go off course, and stormwater may sheet off a driveway, so you’ll want the hardiest, most forgiving plants. But that doesn’t mean you have to compromise on beauty.
Adding a Channel Drain
Sometimes the natural terrain offers no choice but to pitch the driveway down toward the garage. To prevent water from getting inside or undermining its slab, you can install a channel drain (also known as a trench drain). This is something like a heavy-duty roof gutter that’s sunk into the driveway at its low spot. A grille cover sits flush with the driving surface, and the whole system is designed to handle automobile traffic. The size of the drain will depend on the volume of water to be handled, and it typically rests on the subbase and matches the level of the driveway asphalt and garage’s concrete slab. The pitched drain gets connected to underground PVC piping, also pitched, to deliver the collected water to daylight or to a dry well, which the driveway contractor can also install.