Algae forms on stone pavers when moisture, shade, and organic debris combine — remove it with a diluted white vinegar solution (1:1 water/vinegar), a stiff brush, and a pressure washer set below 1,500 PSI. In Los Angeles, algae growth is heaviest in shaded north-facing areas during the winter rainy season. Left untreated, algae creates a dangerous slip hazard and permanently stains porous stone. Black and green algae removal from natural stone pavers takes 1–3 hours for most residential patios and costs $0–$8 per square foot depending on method. Tegula Stone's independent local pros across LA's micro-climates guides this complete removal and prevention guide.
Algae establishes itself on stone surfaces when three conditions are present: moisture, shade, and a porous surface. Understanding your specific situation determines the right treatment and prevention strategy.
North-facing patios, surfaces under mature trees, and areas near pools or water features stay damp longer than sun-exposed stone. Algae thrives in low-light, moist environments and can establish on a stone surface in as little as a few weeks of consistently damp conditions. Even LA’s morning marine layer provides enough moisture for algae growth in perpetually shaded spots.
Flat stone surfaces without adequate slope (minimum 1/8 inch per foot) allow water to pool rather than drain. Standing water dramatically increases algae and moss growth rates. Low spots in a patio, sunken pavers, and areas where joint sand has washed out are the most common locations for algae to concentrate.
Travertine, limestone, and sandstone are highly porous and absorb moisture readily — creating the ideal substrate for algae to anchor and grow. Denser stones like granite and quartzite are significantly more algae-resistant. Unsealed porous stone in shaded LA microclimates is virtually guaranteed to develop algae growth within one to two years of installation.
written and reviewed by independent licensed contractors in the Tegula Stone network.
Not every method is appropriate for every stone type. Always test any cleaning solution on an inconspicuous area before treating the full surface, and never use chlorine bleach on natural stone. After chemical treatment, power washing stone pavers at the correct PSI is an effective final step to clear loosened growth.
Dilute white vinegar 1:1 with water and apply generously to the affected area. Allow 30 minutes of dwell time, then scrub with a stiff-bristle brush (not wire) and rinse thoroughly. Safe for most natural stone types. Effective for light to moderate algae growth. Avoid use on polished limestone or marble — the acid can etch polished surfaces.
Dissolve oxygen bleach (sodium percarbonate) in warm water per package directions. Apply to the stone surface and allow 20–30 minutes of dwell time. Scrub and rinse thoroughly. Color-safe, biodegradable, and effective on porous stone including travertine and limestone. Do NOT substitute chlorine bleach — it damages stone surfaces and strips existing sealers.
Effective for removing algae that has been pre-treated with a cleaning solution. Use 1,200–1,500 PSI maximum for natural stone — higher pressures can erode grout joints and damage softer stone surfaces. Always use a fan tip (40° or wider) rather than a rotary/turbo nozzle. Hold the wand at a consistent angle and distance to avoid uneven cleaning patterns.
Commercial-grade algaecide and biocide treatments used by professional stone care services. Best for severe infestations, black algae (which has deeper root systems than green algae), and porous stone that requires careful chemical management. Professional service typically includes surface preparation, treatment application, pressure washing, and sealer application for complete remediation.
Cost depends on the treatment method, severity of algae growth, patio size, and whether sealing is included. The table below reflects 2026 LA market rates for residential stone paver cleaning.
Removing algae solves today’s problem. Preventing regrowth requires addressing the underlying conditions that allowed algae to establish in the first place. Sealing is the most critical prevention step — our guide to the best sealer for natural stone pavers helps you choose the right product for your stone type. These four strategies used together provide the most complete protection.
A quality penetrating (impregnating) sealer fills the pores of the stone and blocks moisture absorption — the primary condition that allows algae to anchor and grow. Sealing is the single most effective algae prevention tool for porous stone types. Apply every 2–3 years for most stone, annually for travertine and limestone in moist or shaded locations.
Ensure the patio surface has a minimum 1/8 inch per foot slope away from the house. Fill low spots with additional mortar or re-set sunken pavers. Consider installing channel drains in persistently wet areas. A surface that dries quickly after rain or irrigation has dramatically less algae growth than one that holds moisture for hours.
More sunlight reaches the stone surface means faster drying and less favorable conditions for algae. Trim overhanging branches to allow direct sun on the patio surface for at least a portion of each day. Even 2–3 hours of direct sun exposure significantly reduces algae growth rates on porous stone in otherwise shaded locations.
A light annual treatment with oxygen bleach solution — even before visible algae appears — kills spores before they establish. Annual cleaning is far less labor-intensive than treating a heavy infestation and helps maintain the appearance of the stone surface year-round. Pair with sealer reapplication every 2–3 years for complete protection.
The density and porosity of your stone type determines how quickly algae can establish and how aggressively you need to treat and seal. Here is a quick reference for the most common natural stone pavers in Los Angeles.
Travertine is one of the most porous natural stone paver types, with natural voids and pits that trap moisture and provide perfect anchoring points for algae. Travertine pool decks and shaded patios in LA almost universally develop algae without annual sealing. Requires the most proactive maintenance program of any common paver type.
Limestone is softer and more porous than granite or quartzite but denser than travertine. In shaded or moist locations, algae typically appears within 1–2 years on unsealed limestone. Sealing every 2 years and annual cleaning keeps limestone patios and pool decks algae-free in LA’s climate.
Pennsylvania bluestone and similar dense sandstones are significantly more resistant to algae than travertine or limestone due to their lower porosity. Algae still establishes on unsealed bluestone in persistently shaded or wet areas but grows more slowly and is easier to remove. Sealing every 3 years is typically sufficient.
Granite is the densest and least porous common natural stone paver. Algae growth on granite is uncommon except in extremely shaded, persistently wet locations. When algae does appear on granite, it responds well to pressure washing alone without chemical treatment. Sealing granite is optional but extends the life of the surface.
Request your free quote this week before our service calendar fills. independent local specialists, no obligation.
Request Free Quote →You don't have to chase every job alone. Homeowners post projects like this and come to you — quote the ones worth your time, keep 100% of what you earn, and run bookings, documents and invoices in one place. No commission, no per-lead fees.
Start free — see contractor plans