Poor drainage is an ongoing threat for Houston parking lots, especially for asphalt parking lots susceptible to water related wear. The longer water sits on a parking lot, the more damage it will do to the pavement, which is why reputable contractors prioritize efficient drainage.
Age, wear and poor construction methods can all result in drainage problems, but there are typically signs that property owners can respond to. If property owners respond to issues quickly, they can be resolved before the parking lot sustains a total failure.
How Can Low Spots Be Detected Before They Become Depressions?
Depressions are low spots on the parking lot that will eventually deteriorate into potholes or total base failures if left unaddressed. Depressions also interfere with the parking lot’s grade and, by extension, its drainage patterns. Water damage is much more likely if the parking lot is developing depressions, but they can be corrected with prompt repairs from a reputable paving crew.
If a property owner suspects low spots are present in the parking lot, they can inspect it using the following methods:
Monitor runoff drainage patterns
Pay attention to how water moves on the pavement while it rains. If water is not moving in the direction of the grade, or if it is moving so slow it is gathering in spots, micro depressions may be forming. This should be obvious even during light rains.
String line or straightedge testing
A straightedge or string line can be used to measure the parking lot’s grade across its surface. Though not as precise as using a laser level, a straightedge or string line can reveal discrepancies as slight as 1/8 an inch, which is enough to cause drainage issues.
Laser level inspections
Pavement contractors are equipped with laser levels that can precisely measure the parking lot’s grade. During a laser level inspection, the pavement team can confirm whether the parking lot is still properly graded at each spot.
Following a significant rain, low spots will remain wet (and reflect light) longer than the surrounding pavement. This can be a reliable low spot indicator.
What Are Common Signs of Water Ponding on a Parking Lot?
If water is ponding on the parking lot, there are issues with the pavement’s slope or drainage structures. Ponding water is typically easy to spot, and if any of the following are true, then water is likely standing on the pavement for too long:
Water remains on the parking lot 60 minutes after the rain stops
If water remains on the parking lot’s surface for an hour or longer, that is a sign that the pavement’s grade is not functioning like it should.
Water collects in the same spots and with the same shape every time
If runoff is gathering in the same spots on the parking lot and forming the same shapes, there are likely grade related issues behind it.
Rings of sediment are present
Once water dries off of the pavement’s surface, it will leave behind dirt and other debris. If sediment rings are present on the parking lot, it is likely caused by ponding water drying out of depressions.
How Can Property Owners Identify Potential Base Failures Early?
Base failures are major weak spots that threaten the parking lot’s overall stability. Over time, base failures tend to worsen and spread, eventually compromising large portions of the pavement. If they are caught soon enough, the pavement team can often perform spot repairs and stabilize the base without the need for total pavement replacement.
Here are some common signs that a parking lot is developing base failures:
Fatigue (or alligator) cracking
Fatigue cracking is also called alligator cracking because it resembles the scales on an alligator’s back. It is an early sign of base weakness and may develop into a total base failure if not addressed.
Surface deflection while under load
If the parking lot pavement is noticeably flexing while under load, it could be a sign that the base is losing support.
Localized rutting
Rutting and other forms of warping are a clear sign of base instability and are a primary cause of potholes.
Potholes
Potholes can be caused by impact damage, excessive wear or water damage to the pavement’s deeper layers. Potholes may result from base subsidence or collapse as well, which can only be fixed by removing the failed pavement and stabilizing the underlying base.
If any of the above are present, contact a reputable pavement contractor and schedule a professional inspection. The contractor will identify what is causing any base failures and recommend the right repair approach.
What Should Property Owners Do if They Find Low Spots, Ponding or Base Failures in Their Parking Lot?
If a parking lot is developing low spots or showing signs of base instabilities (such as pooling water), it is time to consult with an experienced pavement contractor. Over time, pavement flaws like depressions and potholes will worsen and compromise more of the parking lot. A reputable pavement contractor can halt the progression of any damage and fortify the parking lot’s base, extending its life and restoring proper drainage.
Parking Lot Drainage, Low Spots and Base Failure: FAQs
How long should water stay on a parking lot after it rains?
If water is still standing on the surface an hour after the rain stops, the pavement’s grade is not working the way it should. Water that collects in the same spots and the same shapes every time points to a grade related problem rather than a one off storm.
What is the difference between a low spot and a depression?
A low spot is the early stage. Depressions are low spots that have been left unaddressed long enough to interfere with the parking lot’s grade and its drainage patterns, and they eventually deteriorate into potholes or total base failures.
Can a property owner check for low spots without special equipment?
Yes. Watching how runoff moves during a rain will show whether water is travelling with the grade or gathering, and a straightedge or string line can reveal discrepancies as slight as 1/8 an inch. A laser level inspection by a pavement contractor is the precise version of the same check.
What are rings of sediment on a parking lot?
When ponded water dries off the surface it leaves behind the dirt and debris it was carrying. Those rings mark where water has been standing in a depression, so they are a reliable record of ponding even after the pavement is dry.
Is alligator cracking a sign of base failure?
Fatigue cracking, also called alligator cracking because it resembles the scales on an alligator’s back, is an early sign of base weakness. Left unaddressed it may develop into a total base failure.
Does a base failure always mean the parking lot has to be replaced?
No. Base failures worsen and spread over time, but if they are caught soon enough the pavement team can often perform spot repairs and stabilize the base without the need for total pavement replacement.
