You get your driveway pressure washed. It looks amazing for about three weeks. Then, little by little, that dark film creeps back. By six weeks, you’re wondering if the company actually cleaned it at all. Here’s why: pressure washing cleans the symptom, not the disease. And in Northern Virginia’s humid climate, that disease grows back fast.
It’s Not Dirt—It’s Organic Growth That Survives Pressure Alone
That dark, slimy film on your driveway isn’t really dirt. It’s a living ecosystem: algae, mold, and lichen. Pressure washing blasts off the visible layer, but it doesn’t kill the roots. The organism is still alive in the pores of the concrete or pavers, waiting for the right conditions to grow back.
Northern Virginia’s climate is perfect for this stuff. Humid summers, wet springs, and constant shade under trees—that’s what algae and mold love. You get rain, then heat, then humidity, and boom: the roots start fruiting again. A month after pressure washing, you can see the discoloration creeping back. Two months later, it’s almost as bad as it was before.
The homeowner sees the pressure washing company and thinks they did a bad job. The reality is that pressure washing alone was never going to solve the problem. You need a treatment that kills the organism at the root.
The Post-Treatment Step Most Companies Skip—Why It Matters
Professional cleaning companies know this. That’s why the ones that do it right add a second step: after pressure washing, they apply an algaecide or post-treatment product. This chemical kills the algae, mold, and lichen at the root so it can’t regrow.
This treatment costs more—maybe 100 to 200 dollars depending on your driveway size. But here’s the math: with treatment, your driveway stays clean for 1 to 2 years. Without it, you’re hiring someone again in 6 weeks and again every 6 to 8 weeks after that. One treatment equals three or four annual cleanings.
We recommend treatment on every driveway in Northern Virginia. The cost difference is small compared to not having to deal with a dirty driveway year-round. And if you’re selling your home, a clean, treated driveway that stays clean is a huge selling point.
Sealing Pavers and Concrete—When It’s Actually Worth the Money
After cleaning and treatment, the next question is sealing. Sealer creates a protective layer that makes future cleaning easier and extends the time between treatments.
For concrete, sealing is worth it if your driveway is in good shape (no deep cracks) and you plan to stay in the home 5+ years. The upfront cost is 300 to 600 dollars, but it cuts future algae growth by 50 percent and makes cleaning way easier. Without sealing, you’re doing this work again in 12 to 18 months. With sealing, you’ve got 2 to 3 years.
For pavers, sealing is absolutely worth it if they’re exposed to sun and water. Sealer protects the stone, keeps weeds out of the joints, and maintains color. It’s an upfront investment that saves money and looks better for years. Skip sealing and you’ll be repairing sunken pavers and pulling weeds every season.
The honest answer: if you’re treating the algae (which you should), adding sealer makes sense on concrete that’s in good condition and pavers that see sun and weather. It’s not a scam—it’s maintenance that actually saves money.
Want to get your driveway clean and keep it that way? Call Cornerstone Property Care at (571) 307-4223 for a free quote. We’ll walk you through the options and explain exactly what your driveway needs. Serving Haymarket, Gainesville, and throughout Northern Virginia.