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Asphalt Pavement seal application prevents years of water damage

What Does Sealcoating A Parking Lot Really Do?

Everywhere you look, everyone seems to have a different answer to the question “What does sealcoating a parking lot really do? And is it necessary?” Paving experts typically claim that it is not only necessary, but should be done every few years! Some business owners claim it is an unnecessary expense, boasting of parking lots lasting decades without ever being sealed. There’s even a debate on whether it’s ethical to use regardless of its effectiveness due to its damaging effects to the environment. In fact, we managed to find two articles written by the same contractor with one claiming sealcoating is necessary , and the next arguing that his driveway has never been sealed and is just fine.

Today we are going to get to the bottom of this age-old debate once and for all. Is sealcoating a parking lot really all that important? Well in order to answer this question we first need to understand the fundamentals of how asphalt works.

How Your Parking Lot Should Be Paved

The Foundation

Resurfacing Or ReplacingAny quality paving job first ensures that the foundation of the parking lot is going to be a solid one. Vegetation and loamy or silty topsoil is removed to a depth where a proper stone base can be installed. Aggregate and crushed stone (ABC Stone) is the most common stone base used in our region. The pavement installed is only as good as the stone base beneath. Asphalt is a fairly malleable material and overtime shifts in the foundation can lead to cracking, or improper water drainage. Crushed stone aggregate or ABC stone provides a solid base that resists any movement, keeping the asphalt on top from shifting and cracking.

Asphalt Installation

Once the asphalt is installed atop the properly compacted stone base it should be rolled immediately. The pavement should be consistent and have a smooth finish throughout the whole parking lot. As soon as the pavement is installed it begins oxidizing. The oxidation process causes the pavement to change to a greyish color and become brittle instead of malleable like when originally laid. Any movement or failures in the stone base will begin to reflect through the new brittle pavement resulting in cracking and potholes forming. The cracks and pot holes will then be susceptible to water intrusion which causes damage to the asphalt and stone base.

Why Do They Sealcoat the Parking Lot?

sealcoating a parking lot. Freshly resealed

The sealcoat’s purpose is to act both as an adhesive layer holding together any loose aggregate and fines in the asphalt, slowing down the oxidization process and protecting the pavement from chemical penetration, and the elements. Enemy number 1 to the structural integrity of the asphalt is water. When water enters the cracks and holes of the asphalt it quickly erodes at the graded foundation that the road base and asphalt sit upon. This causes the road base to shift, becoming loose, and failing to support the more brittle asphalt surface. When left unsupported the asphalt will crack, creating more gaps for water to seep in, speeding up the erosion process.

The layer of sealcoat applied to the top of the asphalt after paving causes the asphalt, which is slightly permeable, to become completely impermeable. No longer allowing water to seep through the upper layer and damage the graded foundation. With proper grading and sealing a parking lot will last for decades.

Why Do Parking Lots Need to be Resealed?

Many paving professionals recommend that your parking lot should be resealed about every 3 years. But you can in some cases get away with several more depending on where you live. This is due to 2 variables that greatly affect the life of your sealcoat.

1. Sunlight

Sealcoat when exposed to sunlight actually oxidizes much like steel. The resulting slag loses its adhesive properties and separates from the asphalt. Once enough of the sealcoat has rotted away, revealing individual stones in the parking lot, it will allow more water to pass through the asphalt to the foundation.

2. Rainfall

Clearly, the more rainfall an area experiences, the faster the base of a parking lot will erode away. Meaning that the more it rains in an area, the more often the parking lot will need to be resealed. Being in a heavier rainfall state here in North Carolina we recommend that you stick to the average and look at resealing a parking lot every three years. But for those of you in much dryer states, resealing every 5 years or more is not out of the question.

Why Don’t They Sealcoat Roads?

It can be difficult to feel that sealcoating a parking lot is truly important when we look at how long roads last knowing that they are never sealed. This is because Sealcoating a parking lot is designed to repel water, protecting the foundation of areas with lower traffic. The amount of traffic driving on most roads and parking lots keeps the road mostly impermeable. This is due to the roadway being continuously recompacted by the traffic. Furthermore, a sealcoat experiencing the same amount of traffic as a roadway would not last. It would soon wear out exposing sections of the road and causing the roadway to look very bad.


Asphalt Pulverization

Instead, most roadways are coated in what is referred to as slurry seal, chip seal, or micro seal. These products are more accustomed to the higher amount of traffic experienced by these roadways. Finally, the government understands that because they cannot sealcoat the roads with asphalt emulsion sealers, they will need to perform full depth reclamations of their roadways more often than a business owner will with their parking lot due to road base damage.

Is Sealcoating Environmentally Damaging?

Just before we wrap up, we’ll address the concerns about sealcoating a parking lot being harmful to the environment. Many people claim that it can be very harmful to wildlife and ecosystems. The short answer to this question is yes, and no. Sealcoating can be incredibly harmful to the environment and those laying down the sealcoat IF they are using the wrong kind of sealcoat.

A coal tar sealcoat is an older style of sealcoating that is incredibly harmful to any exposed to it. Those laying down coal tar sealers often return home with burned, and reddened skin due to the toxicity of the sealer. It’s so dangerous that many towns and municipalities have banned its use entirely. Instead of using coal tar sealers, asphalt emulsion sealers significantly reduce the negative effects on the environment. This is a much less volatile compound that is safer when exposed to water, and produces significantly fewer toxic fumes. As part of our commitment to the community, Paving Professionals uses only a very advanced polymer modified asphalt emulsion product that is safe for the environment and lasts for years.

So, Do I Really Need to Have Parking Lot Resealed?

Ultimately, the decision is up to you. You now know the purpose of sealer, and the risks of going without it. We recommend getting the opinion of a paving professional in your area before choosing to go without. And inspecting the state of your parking lot about every 3 years. The more rain you are exposed to, the more important it is to keep your parking lot sealed. If you need a professional opinion feel free to contact us for a free inspection and estimate!

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