Integrity Pro Washers Team
Professional pressure washing and soft washing specialists serving San Diego County.
Last updated: 2026-04-29
Why So Many North Park Driveways Showed Algae This April
Algae bloom on San Diego concrete jumped this April after late spring rain mixed with warm afternoons. We pressure washed 14 driveways in North Park between April 14 and April 25, and 11 of them carried visible green or black streaks. Most cleared with a 3500 PSI surface cleaner and a 1% sodium hypochlorite pre-treatment.
Last updated: April 2026
Our route last week covered 30th Street, Ray Street, and a cluster of homes near Morley Field. We expected dust and tire marks. We got algae instead.
The pattern was consistent. North-facing driveways with shade from canopy trees showed the worst growth. South-facing concrete near University Ave looked closer to normal. Same week, same crew, very different results.
What Algae Actually Does to Concrete
Algae looks like a stain. It is not. It is a living film that holds moisture against the surface, feeds on minerals in the cement, and slowly etches the top layer. Left alone, you lose the smooth finish and the surface becomes porous enough to absorb oil and tire rubber faster.
We tested one customer driveway with a moisture meter before and after a rinse. Reading dropped from 18% to 9% within two hours of removing the algae layer. That is the kind of thing you do not see, but the concrete feels it.
How Much Does Pressure Washing a Driveway Cost in San Diego?
For a standard 600 to 800 square foot driveway, our typical North Park job runs $185 to $275. That includes pre-treatment, a hot-water surface cleaner pass at 3500 PSI, and a final low-pressure rinse. Heavy algae or oil stains add $40 to $80.
We charge by condition, not by the hour. A clean-looking driveway with light dust takes 30 minutes. A shaded driveway with heavy biological growth can run 90 minutes for the same square footage.
Algae vs Mold vs Mildew on Concrete
| Type | Color | Where It Grows | What Actually Removes It |
|---|---|---|---|
| Algae | Green to black | Shaded, damp concrete | Sodium hypochlorite plus 3000+ PSI surface clean |
| Mold | Black, fuzzy | Cracks and expansion joints | Soft wash with surfactant dwell |
| Mildew | Gray to white | Surface film in warm areas | Detergent and rinse, no high pressure |
Why High Pressure Alone Will Not Fix It
This is the part homeowners get wrong. Blasting algae with a 4000 PSI tip without pre-treatment knocks down the visible layer. The roots stay. Two weeks later you see it come back, especially after our coastal mornings.
Our pre-treatment is a 1% sodium hypochlorite mix with a surfactant. We let it dwell for 8 to 12 minutes, then surface-clean. The chemistry kills the organism. The pressure removes the dead biofilm. Doing only one of those is why driveways look bad again by June.
What North Park Homeowners Should Watch For
Three things show up before algae becomes obvious:
- Dark streaks running with the slope of the driveway, especially after rain
- A faint green tint near the garage door or the property line where the lawn meets concrete
- A driveway that takes longer to dry than it used to after rinsing it off with a hose
If you see any of those, it is worth a wash now rather than waiting until mid-summer.
How Often Should North Park Driveways Get Pressure Washed?
Most driveways in our area need a wash once every 12 to 18 months. Driveways with heavy tree cover or that sit in shade for most of the day need it every 9 to 12 months. We have repeat customers on Hawley Boulevard who book us yearly because the canopy is so dense.
We do not push the every-six-months schedule that some companies sell. Concrete does not need it that often. We would rather you pay us once a year and have the work hold than pay us twice and barely move the needle.
The Right Tool for the Job
For driveways, we run a 20-inch surface cleaner powered by a 4 GPM hot-water unit. That gives us an even pass with no zebra striping. Wand-only work on a driveway leaves stripes. You see it on jobs done by general handymen.
For the edges, joints, and the apron near the street, we drop to a 25-degree tip and keep the wand 8 to 10 inches off the surface. Closer than that on aged concrete pulls aggregate.
If you are in North Park, Hillcrest, or anywhere along the 30th Street corridor and your driveway has gone darker over the winter, this is the season to handle it. See our North Park pressure washing page for service details, or our main pressure washing page for a full breakdown of what we wash and what we do not. For more on what pressure can and cannot do to concrete, our concrete damage post covers it. If we cleaned a driveway in your North Park block, we would love to hear about it on Google with your street name in the review.
