How to Clean Pavers in Jacksonville: Removing Green Algae, Mold & Black Mildew

If your patio or pool deck has turned green, slick, or spotted with black flecks, you are seeing the most common paver complaint in Northeast Florida. Learning how to clean pavers the right way matters here more than almost anywhere else in the country, because Jacksonville's warm, humid, shaded yards are a near-perfect greenhouse for algae, mold, and black mildew.

The good news is that green algae and surface mold are almost always cosmetic. They sit on top of the concrete paver, not inside it, so the fix is technique, not demolition. The bad news is that the two things most homeowners reach for first, a maxed-out pressure washer and a jug of harsh acid, are exactly what wrecks a paver patio. High pressure blasts the joint sand out and etches the surface, and acids discolor the pigment and burn the very sealer that was keeping growth out.

This guide walks through safe paver cleaning for our climate, the mild-detergent soft-wash method the pros use, when a low-pressure rinse is appropriate, and how to keep a clean paver patio from turning green again a month later.

Quick answer: Clean pavers with a mild detergent or a diluted sodium-hypochlorite (bleach) solution, a soft-bristle brush, and a gentle rinse, then re-sand and re-seal, never with high-PSI blasting or muriatic acid.

• Green algae and surface mold are cosmetic and lift off with soap and a soft brush, not brute force.
• Keep pressure washing under about 1,500 PSI with a 25-40 degree tip held 12+ inches back, or you will erase the joint sand.
• Skip muriatic and other strong acids; they etch concrete pavers and bleach the color.
• The real cure for regrowth is airflow, drainage, fresh joint sand, and a breathable sealer.

Why Pavers Grow Green Algae, Mold, and Black Mildew in Jacksonville

Northeast Florida gives algae and mildew everything they need: heat, moisture, and shade. Concrete pavers are slightly porous, so they hold water at the surface long after an afternoon storm passes. Add our summer dew points in the low-to-mid 70s and the near-daily 3 p.m. downpours from June through September, and outdoor concrete rarely gets a chance to fully dry.

Shade is the deciding factor. The same patio can be spotless on its sunny half and bright green on the half that sits under a live oak or on the north side of the house. That is why homeowners in tree-canopied neighborhoods like Riverside, Avondale, San Marco, and Ortega fight this constantly, while an open, south-facing driveway in Nocatee or a treeless deck in a newer Julington Creek build stays cleaner.

Here is what you are actually looking at:

• Green algae is a living film that thrives on damp, shaded pavers. It is the slick green layer that makes pool decks dangerous and is the easiest of the three to remove.
• Mold and surface mildew show up as fuzzy or powdery patches, often gray or greenish, feeding on organic debris like pollen, oak tannins, and leaf litter trapped in the joints.
• Black mildew (often the black or dark-gray speckling on pool decks and shaded patios) is the toughest. It roots into surface pores and organic buildup and needs a dwell-time treatment, not just scrubbing.

Our February-through-April pollen season deserves special blame. That yellow oak and pine coating is organic food; once it settles into the sand joints and gets rained on, it becomes fuel for mold on pavers and black mildew pavers for months afterward.

How to Clean Pavers Safely: The Soft-Wash Method

The professional standard for how to clean pavers is "soft washing," which means letting chemistry do the work at low pressure instead of relying on brute force. This is the method that removes the growth without stripping sand or scarring the surface.

Work on a dry, overcast day if you can. Direct summer sun dries the cleaning solution before it can dwell, and you want the pavers cool to the touch. Here is the sequence:

• Clear and pre-rinse. Sweep off leaves and debris, then rinse the surface with a garden hose to knock down loose material and pre-wet the joints so the cleaner stays on top instead of soaking straight down.
• Mix a gentle cleaner. For light green algae, a squirt of mild dish detergent or a dedicated paver/concrete cleaner in a bucket of water is plenty. For stubborn mold and black mildew, a diluted sodium-hypochlorite solution (household bleach cut roughly 1 part bleach to 4-5 parts water) is the standard pro treatment.
• Apply and let it dwell. Spread the solution with a pump sprayer or watering can and let it sit 8-15 minutes. Do not let it dry out; mist it lightly if it starts to. Dwell time is what kills black mildew at the root.
• Agitate with a soft brush. Use a stiff-nylon deck brush, never a wire brush. Scrub along the joints and over the growth. You will see the green lift almost immediately.
• Rinse low and slow. Rinse with a garden hose or a pressure washer on a wide, low-pressure tip. Rinse toward a drain or the lawn, away from the pool and planting beds.

Protect your landscaping. Bleach and lush Florida foundation plantings do not mix, so pre-wet nearby beds, cover delicate plants, and rinse any overspray immediately. Keep pets and kids off until everything is rinsed and dry.

Paver Problems, Causes, and Fixes at a Glance

Not every stain is algae, and the fix changes with the cause. This table sorts the most common issues we see on Jacksonville concrete pavers so you treat the right problem. Note that white haze and washed-out joints have their own dedicated fixes, linked below, because they are not cleaning problems at all.

If the "stain" you are chasing is actually a chalky white film, that is efflorescence, and scrubbing or bleaching will not touch it. We cover that separately in our guide to sealing pavers in Florida humidity. And if the joints themselves look empty or the sand keeps disappearing, read our fix for joint sand washing out before you clean, because cleaning washed-out joints will only make them worse.

How to Clean Pavers Without Blasting Out the Joint Sand

Pressure washing is not banned, but it is the number-one way Jacksonville homeowners accidentally damage a good patio. A pressure washer moves water fast enough to scour sand out of every joint in seconds, and once the joints are empty the pavers shift, weeds move in, and the whole field starts to spread apart. If you are going to use a pressure washer as part of how to clean pavers, follow these limits:

• Keep it under roughly 1,500 PSI. Most consumer machines run 1,800-3,000 PSI, so throttle down or step back. On concrete pavers, more pressure never means cleaner, it means damaged.
• Use a wide tip. A 25-degree (green) or 40-degree (white) tip spreads the force. Never use the red 0-degree tip; it will carve a line right into the paver.
• Hold the wand 12-18 inches back and keep it moving in smooth, overlapping passes. Never dwell on one spot.
• Fan across the joints, not into them. Sweep parallel to the paver surface so you are lifting the film, not drilling into the sand lines.
• Expect to re-sand afterward. Even careful washing pulls some sand. Plan to top off the joints once everything dries.

Honestly, for algae and mildew the pressure washer is optional. The soft-wash chemistry does the killing; a garden hose does the rinsing. Save the pressure washer for a final light rinse, not the main event.

What NOT to Do When Cleaning Pavers

A few popular shortcuts do lasting damage to concrete pavers. Avoid these entirely:

• Muriatic or other strong acids. Acid etches the cement surface, permanently dulls and lightens the pigment, and can trigger fresh efflorescence by pulling minerals to the surface. It also destroys any sealer. There is no safe DIY acid wash for a colored paver patio.
• Zero-degree pressure tips. The pencil-jet tip carves visible stripes and gouges into the paver in a single pass.
• Wire brushes and metal scrapers. They scratch the surface and leave rust-colored streaks that then stain.
• Cleaning right before rain. A bleach treatment needs to dwell and then dry. Our afternoon storm pattern can rinse it off before it works, so check the radar first.
• Sealing over the growth. Sealing a damp or still-dirty patio traps algae and moisture underneath, which clouds the sealer and locks the stain in. Always clean, then let it dry a full 24-48 hours, then seal.

If you want to remove algae from pavers and keep the color intact, mild and patient always beats strong and fast.

Preventing Regrowth on Shaded Patios and Pool Decks

Cleaning is only half the job. In our climate, an untreated patio can be green again within a month if nothing changes. The goal is to give the surface a chance to dry and to remove the organic food supply. What actually works in Jacksonville:

• Improve airflow and light. Trimming back the oak, crepe myrtle, or palm limbs shading a patio does more than any cleaner. More sun and breeze equals faster dry time equals less algae.
• Fix standing water. Low spots and poor drainage keep pavers wet for hours. On pool decks especially, make sure water sheets off toward drains, not into shaded corners.
• Keep the joints full and debris-free. Blow off pollen and leaves regularly, particularly during the spring pollen dump. Debris in the joints is the food source for mold and mildew.
• Re-sand and seal. Fresh joint sand and a quality breathable sealer make the surface far less hospitable and dramatically easier to rinse clean next time.
• Do a quick maintenance rinse. A light soap-and-water wash a couple of times a year prevents buildup so you never face a fully green deck again.

When to Re-Sand and Re-Seal After Cleaning

Any real clean paver patio project ends with two steps most homeowners skip: refilling the joints and re-sealing. Cleaning, especially with any pressure, removes sand and wears at the sealer, so finishing the job is what makes the results last.

• Re-sand when the joints sit below the paver chamfer, sand is visibly missing, or you used a pressure washer. Polymeric sand locks the joints, resists washout in our heavy rains, and helps block weeds. Our polymeric joint-sand fix covers exactly how to do this in a wet climate.
• Re-seal when water no longer beads on the surface, the color looks dull and faded, or it has been a few years since the last coat. Seal only after the pavers are clean and fully dry, and follow the humidity timing in our Florida sealing guide, because sealing in the wrong conditions traps moisture and clouds the finish.

Sequence matters: clean first, let it dry 24-48 hours, re-sand, then seal. Doing it out of order is how patios end up hazy or with sand locked under a milky film.

DIY vs. Professional Paver Cleaning

A single-season green film on a small patio is a very reasonable DIY afternoon. Soap, a soft brush, a pump sprayer, and a garden hose will handle most algae. Where it makes sense to bring in help:

• Large pool decks or wide driveways where dwell time and even coverage are hard to manage solo.
• Deep-set black mildew pavers that keep coming back after DIY treatment.
• Patios that also need re-sanding and sealing, since doing all three in the right order and right weather window is where the durable results come from.
• Any surface where you are unsure whether the stain is algae, mold, efflorescence, or a worn sealer, because the wrong treatment can make it worse.

A pro brings soft-wash equipment that cleans at safe pressure, the right dilution for our humidity, and the sanding-and-sealing follow-through in one visit. If you would rather not diagnose it yourself, that is exactly what our Jacksonville team does. You can also see the rest of our paver services on our homepage.

Frequently Asked Questions