Why Proper Drainage Is Important For Your Parking Lot

Ask any paving contractor what destroys parking lots, and most will give you the same one-word answer: water. Heavy traffic, sun and winter all play a part, but water is the thing that turns ordinary wear into holes, sunken areas and failed sections. For business owners, HOA boards and property managers, understanding drainage is one of the best ways to protect the money tied up in a lot.

How water damages asphalt

Asphalt itself handles rain on its surface reasonably well. The trouble starts when water stays put or gets underneath.

It softens the base

A parking lot gets its strength from the compacted aggregate base and soil below the asphalt. When water seeps through cracks or in from the edges, that base loses its ability to carry weight. Cars and trucks then flex the asphalt over a soft spot, and it starts to crack in an alligator pattern, then break up.

It freezes and expands

In New Jersey, water that gets into pavement during a winter rain may freeze overnight. Ice takes up more room than water, so it pries cracks wider and lifts sections of the surface. Repeat that cycle dozens of times over a winter and the lot comes out of it in far worse shape than it went in.

It weakens the surface

Standing water combined with traffic, salt and fluids dripping from vehicles speeds the breakdown of the asphalt’s surface, which leads to raveling and pitting.

Signs your lot has a drainage problem

You do not need special equipment to spot drainage issues. Walk the lot during or right after a heavy rain and look for:

• Puddles that are still there hours later.
• Water running toward the building entrance or sidewalks instead of away from them.
• Catch basins with water pooling around them rather than flowing in.
• Sunken or cracked areas around inlets.
• Sediment, leaves or debris collecting in the same spots after each storm.
• Edges breaking off where water sheets off the lot into landscaping.

For a closer look at why puddles form and what to do about them, see how puddles form in an asphalt parking lot.

What good drainage looks like

A properly built parking lot moves water off the surface quickly and in a controlled way. That depends on:

• Correct slope. The surface needs enough pitch to carry water to inlets, swales or edges, without low spots where it can collect.
• Working inlets. Catch basins and drains must be set at the right height relative to the surrounding pavement and kept free of debris.
• Protected edges. Where the lot drains to landscaping, the edges need support so runoff does not undermine them.
• A solid base. A well-compacted aggregate base drains better and resists softening when some water does get in.

How drainage is corrected

Fixing drainage often happens alongside repaving. Depending on the lot, that may involve:

• Milling the surface and adjusting grades in the new asphalt so water flows where it should.
• Excavating and rebuilding sunken areas around catch basins.
• Removing and rebuilding failed sections where saturated base has given way.
• Re-pitching problem areas so they shed water instead of holding it.

Because every lot has its own layout and grade, these decisions should be made on site.

Regular habits that help

Between projects, simple routines keep water moving. Clear inlets after storms, especially in fall when leaves come down. Sweep sand and debris that can clog drains. Keep irrigation from spraying the pavement. Have holes and broken areas looked at promptly, since every opening gives water another way in. Our article on potential problems that can damage your parking lot covers other threats worth watching.

Get drainage right from the start

Whether you are repaving or rebuilding, drainage should be part of the plan from day one. We serve commercial properties, HOAs and property managers throughout Monmouth County, Ocean County from Toms River north and southern Middlesex County. Learn more about our parking lot paving and repaving service and set up a free on-site estimate.