If you’re investing in commercial parking lot paving, you might be thinking about surface materials, layout, or traffic flow. But here’s something that gets overlooked far too often: drainage design.
Water is one of the most destructive forces for asphalt. Without a proper drainage plan in place, your brand-new parking lot can start breaking down before the paint even dries. Cracks, potholes, pooling, and erosion—these are just some of the issues that stem from poor water management.
So before you sign off on that paving project, let’s dig into why drainage matters—and how it can save you thousands down the line.
The Real Cost of Ignoring Drainage
Let’s be blunt: if water doesn’t have a place to go, it will find one. And it won’t be where you want it.
Here’s what improper drainage leads to:
- Potholes and Cracks – Water seeps in, freezes, expands, and causes cracks that worsen with every freeze-thaw cycle.
- Surface Erosion – Standing water can weaken the surface layer of your asphalt, especially in high-traffic areas.
- Flooded Entrances – Pooling near building entry points or loading docks creates safety hazards and damages nearby infrastructure.
- Shorter Pavement Life – Asphalt surfaces with poor drainage often fail years before their expected lifespan.
- Increased Liability – Pooling water increases the risk of slips, falls, and vehicle accidents.
Drainage isn’t just a design consideration. It’s an insurance policy for the long-term health of your investment.
What Proper Drainage Design Looks Like
A good drainage system starts before the first drop of asphalt is laid. Here’s what goes into it:
1. Site Grading
Before any paving begins, the entire lot should be graded to promote water runoff. This involves sloping the surface in the right direction—usually 1% to 2%—so gravity can do its job.
2. Catch Basins & Storm Drains
Strategically placed catch basins collect water and direct it to the municipal storm sewer. Poor placement (or worse, none at all) means water builds up in low points.
3. Curbing and Gutters
Curbs help channel water away from the asphalt. Gutters collect and move it efficiently to storm drains. Without them, water spreads uncontrolled.
4. Permeable Materials (Where Applicable)
For environmentally conscious builds, permeable asphalt or interlocking pavers can help reduce runoff by allowing water to seep into the ground.
5. Drainage Infrastructure Maintenance
Even the best drainage systems need upkeep. Clogged drains, cracked pipes, and blocked catch basins are all too common.
How 5 Star Paving Designs for Drainage from Day One
At 5 Star Paving, drainage is not an afterthought—it’s a core part of our commercial paving process.
Here’s how we make sure your parking lot stays strong and dry:
- Site Assessments: Every project starts with a proper grade review and drainage plan.
- Smart Drainage Layouts: We determine exactly where and how water will flow, and plan around it.
- Top-Grade Materials: We use quality aggregates and asphalt mixes designed for heavy weather wear.
- Professional Equipment: Laser grading and GPS layout tools give us pinpoint accuracy for slope and flow.
- Post-Paving Support: We provide maintenance schedules and check-ins to keep your system in top shape.
Common Drainage Mistakes to Avoid
Some mistakes we see far too often include:
- Flat Surfaces: A completely flat parking lot might look nice, but it will guarantee standing water.
- Not Enough Drains: One or two catch basins for a large lot won’t cut it.
- Ignoring Subgrade Conditions: Clay-heavy or poorly compacted soil will hold water under your asphalt, leading to soft spots and failure.
- No Maintenance Plan: Even the best drainage system won’t last if you’re not cleaning out the basins and checking for damage.
Real-World Example: What Bad Drainage Looks Like
One Ontario-based commercial lot (not ours!) skipped grading and only added one drain—on the wrong side of the slope. Within 6 months, water was pooling near entrances. By winter, the surface had split, water seeped in, and potholes formed. The company spent over $45,000 on repairs within the first year.
That’s why 5 Star Paving doesn’t take shortcuts.
Drainage FAQs
1. What’s the ideal slope for a parking lot?
Between 1% and 2%—enough to move water without feeling like a hill.
2. Can drains be installed in an existing lot?
Yes, but it’s more expensive and often disruptive. Planning for it from the start is cheaper and more effective.
3. How often should drains be cleaned?
At least twice a year—spring and fall—plus after major storms.
4. Can poor drainage void warranties?
Yes. Many asphalt warranties are void if water damage is the cause of deterioration.
5. Does my parking lot need curbs and gutters?
If you have significant rainfall or snowmelt in your area (hello, Ontario!), yes—it helps guide water efficiently.
Planning a Commercial Parking Lot? Start with Drainage.
If you’re building or repaving a parking lot, remember: a great surface means nothing if it doesn’t drain properly.
Whether you manage a retail plaza, municipal facility, or industrial yard, 5 Star Paving will build your lot to last—with drainage that protects your investment.
Book a Free Drainage Assessment Today
Get ahead of costly repairs. Contact 5 Star Paving to book a no-obligation drainage consultation for your next commercial project. Let’s build something that lasts.