Overview

Low spots can affect how asphalt drains and may develop for several different reasons. In this blog, CSI Paving, Inc explains how much standing water is normal, what causes depressions to form, when they can contribute to pavement damage, and how contractors repair them. We’ll also look at whether sealcoating can help prevent problems with standing water.

Introduction

After a night of heavy rain, your car rolls through a parking lot or your driveway, sending water splashing from puddles that have collected across the asphalt. You can’t always avoid these spots, and a single downpour can reveal just how in demand this asphalt repair really is. Is there any way to prevent low spots from forming in the first place? Is it anything more than a minor inconvenience?

Low spots don’t appear without a reason. Changes above and below the pavement can gradually affect its shape, slope, and ability to shed water properly. Understanding what’s happening beneath those puddles can help you determine whether you’re dealing with a minor surface issue or a problem that warrants repair and how to keep the same problem from developing again.

How Much Water Should an Asphalt Driveway Hold?

Asphalt pavement isn’t designed to hold standing water. A properly graded driveway or parking lot should instead direct runoff toward its edges, gutters, or drains rather than trap it in low spots. That doesn’t mean every correctly paved surface will be bone-dry immediately after rain. Minor surface irregularities can leave shallow water temporarily, especially during or immediately following heavy rainfall.

A good paving and drainage system should:

Direct runoff away from the pavement toward designated drainage areas
Maintain a consistent slope that keeps water moving across the surface
Prevent significant pooling in isolated areas after rainfall
Maintain positive drainage without depressions interrupting the path of runoff

Rather than focusing on a specific amount of water, pay attention to where it collects and how long it remains. Water that repeatedly settles in the same depression after rainfall can indicate a low spot that’s disrupting the pavement’s intended drainage.

Can Standing Water in a Low Spot Damage Asphalt?

A low spot doesn’t necessarily mean your asphalt is being damaged every time it rains. An intact asphalt surface is relatively water-resistant, so a shallow puddle that evaporates isn’t automatically a structural problem. However, repeatedly trapping water in the same depression can become more concerning as the pavement ages or develops openings.

Water can enter through cracks, joints, porous areas, and damaged edges and eventually reach the aggregate base or subgrade beneath the asphalt. If those supporting materials become saturated, they may lose strength or stability. Heavy loads can then cause the poorly supported pavement to flex, settle, or deform further.

This can create a cycle in which an existing low spot traps water, weakened support allows additional settlement, and the resulting depression holds even more water. The severity depends on the condition of the pavement, how long water remains, and whether it has a path into the underlying structure.

What Causes Low Spots in Asphalt?

Standing water can sometimes be a symptom and a contributor at the same time. Low spots can develop because of problems at the asphalt surface, within the pavement structure, or in the subgrade beneath it. Identifying where the depression originated helps determine why water is collecting and what will be required to correct it.

Some of the most common causes include:

Poor Asphalt Compaction

Asphalt compaction is the process of pressing freshly placed asphalt into a dense layer using heavy rollers and other equipment. This step closes excess air spaces within the asphalt and helps the material form a firm surface capable of supporting traffic without shifting under routine loads.

When asphalt isn’t compacted sufficiently, loosely packed areas can continue to compress after the pavement enters service. Vehicle weight may gradually push these areas lower than the surrounding surface, creating depressions where water collects. Depending on the extent of the problem, contractors may remove the affected asphalt, correct any underlying deficiencies, and repave and compact the area.

Subgrade Settlement Beneath the Asphalt

The subgrade is the native or prepared soil that supports the pavement structure from below. Settlement occurs when that soil sinks or shifts after construction. Since every pavement layer depends on this foundation for support, even localized settlement can pull the asphalt surface downward with it.

As the pavement sinks, the resulting depression interrupts the intended drainage slope and begins collecting water. If this is the problem that’s responsible for the low spot, simply adding asphalt at the surface may leave the underlying problem unresolved. Contractors may need to excavate the affected area, rebuild the base, and repave the surface at the proper elevation. Sometimes, the soil or natural conditions aren’t ideal for pavement support, making an issue like this more likely.

Inadequate Asphalt Pavement Thickness

Asphalt needs enough thickness to support the loads placed on it without excessive flexing or deformation. If the pavement is too thin for the traffic and site conditions, repeated pressure can gradually push sections downward. That’s when depressions develop. The appropriate thickness depends on how the pavement will be used and the support provided by the layers beneath it.

Contractors base thickness on:

Expected vehicle weight and load
Frequency of traffic
Strength and stability of the subgrade
Depth and condition of the aggregate base
Intended use and expected pavement life

If the thickness was designed for a lighter load than the asphalt is facing, contractors may have to remove and replace the affected pavement with a thicker asphalt section designed to support the actual traffic demands.

Poor Asphalt Grading and Drainage

Contractors prepare and contour the underlying material to create the elevations needed to move rainwater toward the many drainage points. That grade provides the profile the finished asphalt will follow once the paving and compaction work begins.

Problems arise when the prepared surface contains incorrect elevations, often areas that are too flat to move water effectively. The asphalt placed over that foundation can carry those irregularities into the finished surface, which means once it’s in use, runoff may slow or collect in certain areas instead of following its intended path.

When this is the cause of pooling, you can often get a clue from when and where the puddling appears. If water has collected in the same areas since the pavement was installed, the original grade may be responsible.

Failed Asphalt Patches and Repairs

Low spots can also develop when an earlier repair doesn’t address the actual source of the damage or isn’t suited to the conditions in that area. A contractor might misdiagnose why the pavement failed, for instance. The repair might look fine when finished but behave differently from the surrounding pavement once traffic and weather begin acting on it.

For example, filling a depression without rebuilding a failed base can allow the repaired area to sink again under traffic. A patch installed too low, meanwhile, can create its own collection point for runoff. Whatever the cause, the next repair needs to address the specific underlying problem and correct any deficiencies that may have been introduced during the previous work.

Are Low Spots a Strong Candidate for Asphalt Repair?

Some of the repair options for low spots have been discussed above, but repair isn’t always the right approach. Contractors first need to determine if the problem can be corrected within a limited area or if replacing a larger section of pavement will provide a more appropriate solution.

Repair is often suitable when the:

Low spot is confined to a relatively small area
Surrounding pavement remains structurally sound
Cracking and deterioration are limited around the depression
Underlying base can be corrected without rebuilding a larger section
Drainage problem can be restored through a localized repair
Pavement still has substantial service life remaining

Regardless of the scope, addressing a low spot early can help keep a manageable drainage issue from contributing to more extensive pavement damage.

Does Sealcoating Protect Asphalt From Standing Water?

Sealcoating is a protective coating applied over the surface of existing asphalt pavement. Most sealers are made from an asphalt- or refined coal tar-based emulsion blended with water, mineral fillers, and other additives. Once spread across the pavement and allowed to cure, the coating forms a thin surface barrier that helps limit exposure to substances that contribute to deterioration.

Sealcoating can help reduce water penetration through the pavement surface, but it won’t prevent standing water or correct a low spot. Proper drainage still depends on the shape and slope of the pavement. Sealcoating is instead used periodically as preventive maintenance, helping protect the surface after drainage problems and necessary repairs have been addressed.

Get Lasting Asphalt Repairs for Low Spots and Puddles

CSI Paving, Inc provides commercial and residential asphalt repairs that target the source of low spots and restore proper drainage to your pavement. We handle problems big and small, giving damaged areas the attention they need to keep water moving and your asphalt performing as intended.

Call (310) 612-1359 today to get the work you need from an expert team.

CSI Paving, Inc

Why Does Asphalt Develop Low Spots and Puddles?