Your Patio's Been Sitting Under All That Rain, and You Don't Even Know It Yet
I'll tell you what—I've watched enough patios from the tree line to know exactly what happens between November and March. Winter doesn't just leave your concrete wet. It leaves it colonized. Algae, mold, mildew—they move in quietly while you're inside drinking coffee, and by the time you notice the dark blotches creeping across your pavers, they've already started eating into the surface itself.
The problem is timing. Most people don't think about pressure washing patio surfaces until May or June, when the sun's warm and entertaining season is right around the corner. But that's exactly backward. You're not just cleaning at that point—you're fighting three months of established growth. The stains have set. The moisture has penetrated. And now you're looking at either professional-grade restoration or accepting that your beautiful outdoor space looks like it belongs in a neglected corner of the forest.
Here's what happens if you wait: that mold and mildew don't just sit on top of your concrete or pavers. They work into the porous surface, especially if you've got natural stone. Once they're in, they're converting the mineral structure itself. A few summers back I watched a neighbor put off spring cleaning for two years straight—too busy, he said. By year three, he was calling contractors about replacing half his patio because the stains wouldn't wash out and the pavers had started to cup and crack from moisture damage underneath.
Why March Is the Only Month That Actually Matters
Now here's the thing: March is your narrow window. Rain's still frequent enough that you won't trigger a drought, but the temperatures are climbing just enough that surfaces dry faster than they do in January. That matters more than people realize. A wet patio in January stays wet for days. A wet patio in March dries in an afternoon, which means the moisture doesn't have time to drive deeper into your concrete's pores.
You're also getting ahead of the real rainy season. Most of the Pacific Northwest sees another wet period in April, and if your concrete's already clean and you've sealed it properly afterward, water slides right off instead of settling in. The mold and mildew spores that would normally take root in early spring find nothing to grip. Prevention works better than cure—always has, always will.
The other reason to move fast: concrete mold removal gets exponentially harder the longer you let it sit. Fresh mold is mostly surface growth. Six-month-old mold is entrenched.
What a Real 3-Hour Deep Clean Actually Looks Like
Don't confuse a quick spray-down with a proper pressure washing. Folks call it "pressure washing" like there's only one way to do it, but there's a world of difference between running a 1,500 PSI homeowner rig over your deck for 45 minutes and doing an actual job.
Here's the breakdown:
- Hour One: Surface Assessment and Pre-Treatment — You're not just blasting. You're looking at what you're dealing with. Concrete? Pavers? Flagstone? Each material needs different PSI and nozzle angles. You apply a biodegradable algaecide or moss killer to the worst growth spots and let it sit for 20 minutes. This softens the mold and mildew so you're not just pushing them around; you're actually killing them and lifting them out.
- Hour Two: Main Pressure Washing — Now you come in with the equipment. A solid electric pressure washer runs 2,500–3,000 PSI—enough to bite through buildup without cratering your concrete. You work in sections, overlapping your passes so you don't miss edges. On pavers, you need to go slower and keep your nozzle at a wider angle. Rush it and you'll blast the polymeric sand right out of the joints.
- Hour Three: Detail Work and Drying Prep — Corners, crevices, the spaces between pavers where mold loves to hide. You finish with a lower-pressure rinse to clear any remaining chemical residue, and then you just let the March sun and wind do their job.
The Paver Stain Prevention That Saves You Later
After your patio is clean—actually clean, not just surface-level clean—you've got a narrow window to seal it. Most people skip this step entirely. They wash, they look at their beautiful blank pavers, and they think the job's done.
Wrong. The cleaning just finished the prep work.
A quality penetrating sealer (look for solvent-based polyurethane or acrylic, not the water-based stuff that washes off in a season) soaks into the porous surface and creates a barrier that repels moisture and staining agents. Paver stain prevention isn't about keeping things perfect—it's about buying yourself time. Next spring, when fresh mold tries to take hold, it's starting from a protected surface instead of bare, porous stone.
Apply sealer within 48 hours of pressure washing, when the surface is completely dry. You're looking at maybe 2–3 coats depending on how porous your pavers are. A 5-gallon bucket of good sealer runs about $60–$90 and covers roughly 400 square feet per coat. That's insurance against a $1,200 concrete replacement job.
What Happens If You Skip Spring and Wait Until Summer
I'm not trying to scare you. But I've watched this play out enough times to be blunt about the economics. If you skip March and June rolls around, you're not just doing extra work—you're fighting months of permanent staining. Outdoor surface cleaning in March takes three hours. Outdoor surface cleaning in June takes three days, costs 40% more, and you're still not guaranteed the stains will fully come out.
By August, when the concrete's been baking under the sun and the stains have had time to oxidize and bond with the mineral surface, you're past pressure washing. You're into acid washing, which etches the concrete and requires professional handling. Beyond that, you're replacing sections. The math gets ugly fast.
Listen—the only reason homeowners end up with those $1,200 repair bills is because a $400 cleaning and sealing job in March didn't happen.
Spring Patio Maintenance: The Real Checklist
Spring pressure washing isn't a standalone task. It's the foundation of the whole season. Once your patio's clean, you've got a few more things worth doing while you're out there.
- Check for cracks in concrete that might have widened over winter—a little concrete filler now prevents water from driving deeper later
- Clear debris from paver joints and reapply polymeric sand if needed (sweep it in dry, mist lightly to set)
- Inspect the base for drainage issues; if water pools instead of running off, you're setting yourself up for frost heave next winter
- Edge the pavers or concrete where it meets the lawn—keeps grass roots from working underneath and creating soft spots
None of this is complicated. It's just maintenance. The kind of thing that takes an afternoon in March and saves you from a crisis in July.
The Equipment Question
You can rent a pressure washer for about $70 a day, which makes DIY tempting. And look, if you're comfortable with the equipment and you've got the time, go for it. I'm not saying professionals are the only way. But be honest with yourself about whether you'll actually do a thorough job. Most people don't.
Professional pressure washing for a standard residential patio runs $300–$600 depending on size and how bad the mold damage is. Add sealing and you're at $500–$800 total. That sounds expensive until you remember it prevents the $1,200 replacement that happens when you don't do it.
Last Thought on Spring Patio Pressure Washing
Your patio's been through a wet winter. It's earned a cleaning. Do it now while the timing's perfect and the work's still within normal range. Wait until summer and you're not cleaning anymore—you're repairing. The only difference between a five-year-old patio that looks brand new and one that looks beat to hell is usually this single March afternoon.