Sealcoat or resurface: which your lot actually needs

Sealer is paint for asphalt, in the sense that it protects what is there and fixes nothing underneath. That one sentence settles most of the arguments about what a parking lot needs. If what is there is sound, seal it. If it is not, sealing it is money spent on hiding the problem until spring. Here is how I read a lot, stage by stage, and what each stage calls for.

Stage one: gray and fine-cracked

The asphalt has gone from black to gray, the surface feels dry and sandy, and there is fine cracking, hairlines and a few longer cracks, but the surface is flat and firm and nothing moves under a truck. This is oxidation: the sun has burned the light oils out of the binder at the surface. It is the stage sealer was made for. Clean it, fill the cracks hot, two coats of sealer with sand, stripes, and the lot is protected for three years. A lot kept at this stage never leaves it.

Stage two: open cracks, a few failures

Cracks you can put a finger in, some of them branching; a pothole or two where the plow caught an edge; a patch of alligator cracking near a drain or a dumpster pad where the trucks turn. The lot is still mostly sound. This is a repair-and-seal year: crack filling for the open cracks, cut out and patch the potholes and the alligatored area down to the base, then seal the whole lot. Sealer over an alligatored area without patching lasts one winter.

Stage three: alligatored and rutted

Alligator cracking across large areas, ruts in the drive lanes where the trucks run, edges crumbling, water standing in the wheel paths. The base has failed under those areas, usually from water that got in through the stage-two cracks that were not filled. Sealing this lot is a waste of the sealer. The honest options are an overlay, if the base is sound under most of the lot, or reconstruction of the failed areas with an overlay over the rest. Patching the worst and sealing the rest is a holding action that buys a year or two if the budget is not there; we say so when we quote it.

Stage four: the base has gone

Potholes that come back every spring in the same places, pavement that moves under a car, areas that have sunk below the drains. There is nothing to seal and nothing to overlay; the lot is dug out to the base, the base rebuilt and the lot paved. Twenty-five years of maintenance at stages one and two costs a fraction of this.

What an overlay is

A new lift of asphalt, usually an inch and a half to two inches, laid over the old surface after the failed areas are cut out and the whole lot is milled or tack-coated. It gives a new surface on the old base at a fraction of reconstruction and lasts fifteen or twenty years if the base was sound. It is the right answer for a stage-three lot with a good base, and the wrong one for a lot whose base is the problem, because the old failures come back through the new surface in a few winters.

The two questions

1. Is the failure on the surface or in the base? Surface problems, oxidation, hairlines, open cracks, are sealcoat and crack-fill problems. Base problems, alligator cracking, ruts, moving pavement, sinking, are patching, overlay or reconstruction problems.
2. How much of the lot is at each stage? A lot that is ninety percent stage one with one stage-three corner is a seal with a patch. A lot that is half stage three is an overlay.

What choosing wrong costs

Sealing a lot that needed patching wastes the sealer and delays the patching a year, while the water keeps going into the base. Overlaying a lot that needed its base rebuilt wastes the overlay. Reconstructing a lot that needed an overlay wastes the difference, which is most of the money. We walk every lot before we quote it and we quote the stage it is at, not the service you asked about; sometimes that is a smaller bill than you expected and sometimes it is a bigger one. The arithmetic article works the numbers for a lot kept at stage one against one let go to stage three.