On a still July afternoon in central New Jersey, the surface of a dark parking lot gets far hotter than the air above it. Asphalt is a mix of aggregate held together by a petroleum-based binder, and that binder softens as it heats up. For most of the year that flexibility is a strength. During a heat wave, it is when a parking lot is most vulnerable.
What happens to asphalt when it gets hot
The binder in asphalt behaves a bit like very thick syrup. In cold weather it stiffens; in high heat it relaxes. A properly built lot is designed to handle this, but the softer the surface gets, the easier it is for loads to push it around. Damage that would never happen in October can show up in a single afternoon in August.
Heat damage parking lot owners commonly see
Scuffing and tire marks
Cars turning their wheels while parked, especially in tight spaces and at the ends of drive aisles, can twist the soft top layer and leave scuff marks or small tears in the surface.
Ruts and shoving
Delivery trucks, garbage trucks and box vans that stop, start and turn in the same spots can push softened asphalt sideways. Over time this creates ruts in wheel paths and ripples or bulges near loading areas and dumpster pads.
Dents and depressions
Anything with a small footprint and a lot of weight is a problem on a hot day. Trailer jacks, dumpster wheels, construction equipment, motorcycle kickstands and even portable signs can press dents into the surface that hold water once it rains.
Faster aging
Strong sun and heat also dry out and oxidize the top of the pavement over the years. Aged asphalt turns gray, loses its flexibility and becomes more prone to cracking when winter arrives.
How to protect a lot during hot weather
Owners and property managers can reduce heat damage without much expense:
- Spread out heavy traffic. If you can, schedule large deliveries and dumpster service for cooler morning hours.
- Put plates or boards under point loads. A sheet of plywood under a trailer jack or a dumpster’s wheels spreads the weight and prevents dents.
- Watch the tight turns. Areas where vehicles constantly turn in place are the first to scuff. Note them so they can be built heavier the next time the lot is repaved.
- Clean up fuel and oil. Petroleum spills soften asphalt even more, and a hot day speeds that up. Absorb spills quickly with cat litter or a commercial absorbent and sweep it up.
- Keep the surface draining. Low spots created by heat damage will hold water, and that water is what turns a cosmetic dent into a hole after the first hard freeze.
When heat damage means it’s time for repairs
Small dents and light scuffing are mostly cosmetic. Deep ruts, shoving near entrances, and depressions that hold water are signs the surface or base is not standing up to the traffic. Where the base is sound, the top layer can be milled off and repaved; where it has given way, those sections need a new base. If a lot has heat damage across large areas, it is worth having it looked at before the next winter, because softened, uneven areas break down quickly once freeze-thaw cycles start.
When we pave or repave a lot, we look at where the heavy traffic actually goes and build those areas to carry it. You can read more about how we handle asphalt parking lot paving for commercial properties, HOAs and property managers. For more on long-term care, see our guide to extending the life of your asphalt parking lot, and if you have a home driveway too, our tips on avoiding summer heat damage to your driveway apply on a smaller scale.
Need this done right?
Dan The Paver handles parking lot paving across Monmouth, Ocean (Toms River and north) and southern Middlesex counties. Free on-site estimates.