Seal And Coat - Sealcoating - Number of Coats
Seal coating should always be applied in thin, light coats, not thick, heavy coats. The number of coats your pavement surfaces require mainly depend on their current state, the previous maintenance the pavement has received, and the amount of traffic it is subjected to.
If your home driveway or commercial parking lot has just started to have the bare asphalt exposed, one coat should be sufficient in restoring it and providing several more years of protection. If it has been a long time (4 or 5 years, or more), since you've seal coated, two coats may be required.
On new or never sealed pavement surfaces, most product manufacturers specifications and industry recommendations recommend two coats. This helps ensure you get a quality, long lasting job with maximum protection. Often times, when sealing never before sealed pavement, the rough nature of the pavement causes air bubbles to from which can appear as spots where the sealer failed to be applied or stick. The second coat covers up these spots where air pockets have formed.
On areas subjected to extremely high traffic, such as the entrance and exists of gas stations, fast food restaurants, grocery stores, etc., a third coat may be recommended to ensure you get a long-lasting and quality job. While it may add a slight amount of cost to the project, it is easier and less costly than having to bring a pavement repair crew out to the location after a year when the high-traffic areas have worn away and the rest of the pavement still looks presentable.