Coal Tar vs Asphalt Emulsion Sealer: Which Should Go on a Haverhill Driveway?
September 9, 2026
The two sealers look identical in the bucket and on the driveway; the difference is what they are made of, where they are allowed, and what to ask before the tank is opened.
What is actually in the two buckets
Both products are a black liquid brushed or sprayed onto asphalt to protect it from sun, water and traffic. The difference is the base. Coal-tar-based sealcoat, according to the U.S. Geological Survey, is typically 20 to 35 percent coal tar or coal-tar pitch, a byproduct of coking coal. Asphalt-emulsion sealer uses refined asphalt, the same family of material as the pavement binder underneath, dispersed in water. Both are blended with sand, water and additives, and both cure to a thin film that wears off under tires over two to three years.
That wear is the crux of the environmental argument. The USGS notes that abraded, dried sealcoat particles are carried off a driveway by rain, wind, car tires and feet. Whatever is in the film ends up in the gutter, the lawn and the house.
The PAH number
Polycyclic aromatic hydrocarbons, or PAHs, are the compounds that separate the two products. USGS measurements put coal-tar-based sealcoat at 35,000 to 200,000 milligrams of PAHs per kilogram, about 100 times the concentration in used motor oil and about 1,000 times the concentration in sealcoat with an asphalt base. That thousand-fold gap, not durability, is why the coal tar product has been restricted in a growing list of places.
USGS also notes a regional habit: coal-tar-based sealcoat is more common east of the Continental Divide, asphalt-based sealcoat west of it. Haverhill is deep in coal tar country by tradition, so the question is live here in a way it is not in Denver.
Where coal tar is banned, and where Haverhill stands
Austin, Texas, was the first jurisdiction to ban coal-tar sealants, in 2006. Statewide bans now cover Washington, Minnesota (2014), New York (sales in November 2022, application in November 2023), Maine (sales in October 2023, application in October 2024), Maryland (October 2023) and Virginia (retail sale July 2024, application July 2025), and a Canadian restriction took effect January 1, 2025. Two of those, Maine and New York, are a short drive from the Merrimack Valley.
Massachusetts has no statewide ban as of this writing. The town of Westwood passed the state's first municipal ban on May 4, 2015. A bill in the 2025-2026 session, Senate No. 645, An Act prohibiting the use of coal tar sealers, was filed on January 16, 2025 and referred to the Environment and Natural Resources committee; it has not become law. No Haverhill, Essex County or Plaistow restriction appears in the ban lists checked for this article, so in Haverhill the choice is currently the owner's, and it is worth confirming with the city before a large commercial job.
What matters more than the base in Haverhill
On a Haverhill driveway the sealer base is rarely what decides whether the job lasts. The site's winter pavement data makes the case: 143.4 freezing nights a year, 57.8 inches of snow and a chloride road diet wear any sealer on roughly the same two-to-three-year schedule. What separates a good job from a bad one is preparation, and preparation is identical for either product.
A well-prepared asphalt-emulsion job will outlast a rushed coal-tar job, and the reverse is just as true. The product is one line on the scope; the preparation is the scope.
- Cracks filled with hot rubber before the sealer goes down, not skimmed over with sealer.
- Surface cleaned of sand, salt residue and oil so the film bonds to asphalt instead of dust.
- Two coats applied at 50 degrees F and rising, with the temperature holding above 50 degrees F for the following 24 hours and no rain forecast.
- Full cure before traffic, and striping only after the cure if the job is a lot.
- A repeat visit on a two-to-three-year cycle, with crack filling every year in between.
Questions to ask before the tank is opened
The two products are indistinguishable once applied, so the answers have to come in writing. Ask the contractor which base is in the tank and to name the product on the written scope. Ask for the manufacturer's technical data sheet, which states the coal-tar or asphalt content, the mix ratio, the application temperature and the cure time. Ask how sand and salt residue will be removed, how cracks will be treated and how many coats are included. Those questions matter as much for driveway sealcoating in Bradford as for parking lot sealcoating on a Route 125 plaza, and they are the basis of a fair comparison between bids.
If a lower price is the pitch, find out what was removed to get there. The drivers of cost, from square footage to crack footage to access, are laid out on the cost page; the base material is rarely the biggest one. For a written scope from sealcoating across Haverhill and the surrounding towns, the quote form is the place to start.
More from the blog
- HOA and Condominium Roadway Maintenance Plans in Haverhill
- Downspouts, Sump Lines and Driveway Drainage on Haverhill's Hill Lots
- Why Driveway Edges Crumble on the Merrimack River Flats
Quick Answers
Is coal tar sealer illegal in Massachusetts?
No, not statewide as of this writing. Westwood enacted a municipal ban in 2015, and Senate bill 645 in the 2025-2026 session would prohibit coal tar sealers if it passed, but it was still in committee when checked. No Haverhill restriction appears in the ban lists fetched for this article. Neighboring Maine and New York have banned both sale and application. Rules change, so confirm with the city before a large job.
Which sealer lasts longer, coal tar or asphalt emulsion?
In Haverhill, preparation and weather decide it more than the base material. Both types wear off under tires and plows on roughly a two-to-three-year cycle, both need 50 degrees F and 24 dry hours to cure, and both fail early over unfilled cracks or a dirty surface. Judge bids by crack treatment, cleaning, number of coats and cure time rather than by which base is in the tank.
How can I tell which sealer was used on my driveway?
Usually not by looking; both cure to the same flat black. The reliable route is paperwork: the written scope or invoice should name the product, and the manufacturer's data sheet states whether it is coal-tar or asphalt based. If a previous owner left no records, treat the driveway as unknown, and make sure the next job names the product in writing before it is applied.