Practical Guide: How to Remove Algae, Mould, Moss and Lichens from Stone, Marble and Granite

Outdoor surfaces made of natural stone, marble and granite constantly face rain, moisture and shaded conditions. As a result, algae, mould, moss and lichens on stone can develop over time. Consequently, homeowners often need the removal of moss and lichens from stone to prevent dark stains, preserve visual uniformity and reduce surface slipperiness.

This practical guide explains when to take action, which surfaces are suitable for treatment and which cleaning system to use to remove biological deposits from stone materials while preserving their structure and original appearance.

👉 Discover the cleaning system for outdoor stone and marble surfaces

When This Treatment Is Recommended

This cleaning system is particularly suitable for the removal of moss and lichens from stone surfaces exposed to persistent moisture or prolonged shade. In particular, it is recommended when surfaces show:

• black stains or widespread darkening
• surface biological films
• adherent moss and lichens
• slippery or visually deteriorated surfaces

Moreover, it is effective both for light biological contamination and for more persistent growth, including lichens that are strongly attached to the surface.

Application Surfaces and Environments

This system is suitable for:

• outdoor natural stone flooring
• marble and granite surfaces
• porphyry and similar stone materials
• terraces, balconies and walkways
• courtyards and outdoor areas exposed to moisture

Algae, Mould and Lichens on Stone, Marble and Granite: The Problem

Even the most compact stone materials contain micro-porosity and surface irregularities that encourage the adhesion of microorganisms.

Over time, algae, mould and lichens:

• alter the appearance of surfaces
• promote biological deterioration
• increase moisture retention
• make surfaces more slippery

Furthermore, using unsuitable or overly aggressive products may prove ineffective and can damage the material.

Treatment Principles

A proper treatment allows the removal of biological deposits from stone without affecting the structure of the stone material, even when contamination is persistent.

Therefore, removing biological deposits from stone materials should not be limited to surface washing. Instead, the treatment must:

• act deeply on microorganisms
• promote the detachment of biological films
• allow controlled mechanical removal
• respect the nature of the stone material

In addition, the system described here remains effective even at low temperatures and can be repeated when contamination persists, without damaging stone, marble or granite.

Recommended Cleaning System for Outdoor Stone, Marble and Granite

Phase 1 – Stain Removal and Sanitising Treatment

Apply ALGANET®, a stain-removing cleaner specifically formulated to eliminate algae, mould, moss and lichens from outdoor stone surfaces.

The treatment is carried out using stiff brushes, BROWN BUFFER PAD or BROWN DISC, which help the mechanical action and facilitate the removal of biological deposits, even in the most heavily contaminated areas.

Phase 2 – Rinsing and Finishing Clean

After the stain-removal treatment, rinse the surface thoroughly and clean it with ECOMARBEC, a biodegradable degreasing cleaner that helps to:

• remove residues of degraded dirt
• eliminate any treatment residues
• improve the overall visual uniformity of the surface

➡️ For dilution ratios, contact times, application methods and coverage rates, always refer to the individual product pages.

Treatment Results

Once the treatment is complete, stone, marble and granite surfaces are:

• free from algae, mould, moss and lichens
• more visually uniform
• less slippery
• deeply cleaned
• ready for any subsequent protective treatments

Frequency of Use

This system is recommended for extraordinary cleaning operations, carried out as needed or whenever new biological contamination appears.

In particularly damp or shaded environments, the treatment can be repeated over time without compromising stone materials.