What is driveway sealcoating?

What is driveway sealcoating made of?

Nearly every driveway sealer is one of two bases: refined coal tar or an asphalt emulsion. USGS reports that coal-tar products are typically 20 to 35 percent coal tar or coal-tar pitch: “Most sealcoat products are either coal-tar or asphalt emulsion.” Source: U.S. Geological Survey, read 2026-10-29. “Coal-tar-based sealcoat products typically are 20 to 35 percent coal tar or coal-tar pitch.” Source: U.S. Geological Survey, read 2026-10-29. “Coal tar is a byproduct of the coking of coal, and can contain 50 percent or more PAHs by weight.” Source: U.S. Geological Survey, read 2026-10-29.

How does the USGS describe driveway sealcoating?

Sealcoat is a thin black liquid layer put on top of existing asphalt, not new paving, and homeowners use it on driveways as businesses do on parking lots. The U.S. Geological Survey (USGS) describes it this way: “Sealcoat is the black, viscous liquid applied to many asphalt parking lots, driveways, and playgrounds in North America to protect and enhance the appearance of the underlying asphalt.” Source: U.S. Geological Survey, read 2026-10-29. “Sealcoat is a black liquid that is sprayed or painted on asphalt pavement in an effort to protect and beautify the asphalt.” Source: U.S. Geological Survey, read 2026-10-29. “Sealcoat is used commercially and by homeowners across the Nation.” Source: U.S. Geological Survey, read 2026-10-29. “It is applied to residential driveways and to parking lots associated with commercial businesses (including strip malls and shopping centers), apartment and condominium complexes, churches, schools, and business parks.” Source: U.S. Geological Survey, read 2026-10-29.

What does driveway sealcoating do?

Its job is cosmetic and protective: a fresh coat darkens faded asphalt and puts a wearing layer over the surface. University of Wisconsin-Extension and the U.S. Environmental Protection Agency (EPA) put it this way: “Asphalt sealcoats are used to improve the appearance and prolong the life of driveways and parking lots.” Source: University of Wisconsin-Extension, read 2026-10-29. “Coal-tar sealcoat is a type of sealant used to maintain and protect driveway and parking lot asphalt pavement.” Source: U.S. Environmental Protection Agency, read 2026-10-29. “Sealcoat is the black, viscous liquid sprayed or painted on many asphalt parking lots, driveways, and playgrounds to protect and enhance the appearance of the underlying asphalt.” Source: U.S. Geological Survey, read 2026-10-29.

Oil-based driveway sealcoating

Oil-based sealer usually means an asphalt-based product, the main alternative to coal tar. USGS measured coal-tar sealcoat at 35,000 to 200,000 mg/kg of PAHs, about 1,000 times the level in asphalt (oil) based products: “Coal-tar-based pavement sealcoat typically contains 35,000 to 200,000 mg/kg (parts per million, or ppm) PAHs, about 100 times more PAHs than in used motor oil and about 1,000 times more PAHs than in sealcoat products with an asphalt (oil) base.” Source: U.S. Geological Survey, read 2026-10-29. “Asphalt and asphalt-based sealcoat products have much lower concentrations of PAHs.” Source: U.S. Geological Survey, read 2026-10-29. “For historical and economic reasons, coal-tar-based sealcoat is more common east of the Continental Divide (except in those states, counties, and municipalities where its use is prohibited), and asphalt-based sealcoat is more west of the Continental Divide.” Source: U.S. Geological Survey, read 2026-10-29.

How long does driveway sealcoating last?

Sealcoat is a wearing layer, so it is renewed rather than kept forever. USGS reports manufacturers recommend a new coat every 2 to 3 years, while applicators give a range of 1 to 5 years: “Sealcoat "wear and tear" is visible in high traffic areas within a few months after application.” Source: U.S. Geological Survey, read 2026-10-29. “Sealcoat manufacturers recommend reapplication every 2 to 3 years.” Source: U.S. Geological Survey, read 2026-10-29. “Applicators recommend reapplication of sealcoat from every 1 to 5 years.” Source: U.S. Geological Survey, read 2026-10-29.

Driveway sealcoating and crack filling

Crack filling and sealcoating are two separate treatments: filling puts material into individual cracks, while sealcoat is a coating over the whole surface. The Federal Highway Administration (FHWA) defines the crack treatments for asphalt highway pavement this way: “Crack Filling— The placement of ordinary treatment materials into non-working cracks to substantially reduce infiltration of water and to reinforce the adjacent pavement.” Source: Federal Highway Administration, read 2026-10-29. “Crack Sealing— The placement of specialized treatment materials above or into working cracks using unique configurations to prevent the intrusion of water and incompressibles into the crack.” Source: Federal Highway Administration, read 2026-10-29. On preventive crack filling, FHWA adds: “Depending on the type of cracks to be filled, this may occur as early as between 4 and 8 years after construction or resurfacing.” Source: Federal Highway Administration, read 2026-10-29.

Coal tar sealant ban

Some states and counties ban coal-tar sealer because of its PAH content, while asphalt-based sealer stays allowed. Minnesota Statutes section 116.202 (enacted 2013) bans both use and sale of coal tar sealant on asphalt: In Minnesota, subdivision 2: “Except as provided in subdivision 4, a person shall not apply coal tar sealant products on asphalt-paved surfaces.” Source: Minnesota Office of the Revisor of Statutes, read 2026-10-29. In Minnesota, subdivision 3: “Except as provided in subdivision 4, a person shall not sell a coal tar sealant product that is formulated or marketed for application on asphalt-paved surfaces.” Source: Minnesota Office of the Revisor of Statutes, read 2026-10-29. “In Wisconsin, Dane County has prohibited the sale or application of coal tar-based asphalt sealants.” Source: University of Wisconsin-Extension, read 2026-10-29. At the federal level, USGS wrote in 2005: “Currently, the use of coal-tar based sealcoat is not federally regulated.” Source: U.S. Geological Survey, read 2026-10-29.

Is driveway sealcoating necessary?

Sealcoat is optional maintenance, not a part of the pavement itself, and federal sources list driveways that are never sealed among the alternatives. USGS and EPA name these options: “Possible alternatives to coal-tar based sealcoating of parking lots and driveways include the use of concrete and unsealed asphalt pavement, and the use of asphalt-based sealcoat that contains lower levels of PAHs.” Source: U.S. Geological Survey, read 2026-10-29. “Pavement options such as pervious concrete, permeable asphalt and paver systems do not require sealants.” Source: U.S. Environmental Protection Agency, read 2026-10-29.

Sources

• Coal-Tar-Based Pavement Sealcoat, PAHs, and Environmental Health — U.S. Geological Survey; read 2026-10-29.
• Fact Sheet 2005-3147: Parking Lot Sealcoat: A Major Source of PAHs in Urban and Suburban Environments — U.S. Geological Survey; published 2005; read 2026-10-29.
• Fact Sheet 2016-3017: Coal-tar-based pavement sealcoat - Potential concerns for human health and aquatic life — U.S. Geological Survey; published 2016-04-20; read 2026-10-29.
• EPA 833-F-12-004: Polycyclic Aromatic Hydrocarbons, Coal-Tar Sealcoat, and Stormwater Pollution — U.S. Environmental Protection Agency; published 2018-01; read 2026-10-29.
• Coal Tar-Based Asphalt Sealcoats - A Health and Environmental Hazard — University of Wisconsin-Extension; published 2012-11-08; read 2026-10-29.
• FHWA-RD-99-147: Materials and Procedures for Sealing and Filling Cracks in Asphalt-Surfaced Pavements — Federal Highway Administration; published 1999; read 2026-10-29.
• Minnesota Statutes 116.202 Coal Tar Sealant; Use and Sale Prohibited — Minnesota Office of the Revisor of Statutes; published 2013; read 2026-10-29.