Practical Guide: How to Remove Algae, Mould, Moss and Lichens from Outdoor Terracotta and Clay Surfaces

Algae, mould, moss and lichens on terracotta are a common problem on outdoor terracotta and clay surfaces exposed to rain, persistent moisture, shade and limited sunlight.
Because these biological deposits spread over time, they can darken surfaces, make them slippery and compromise their appearance. This practical guide to cleaning outdoor terracotta explains when to take action and which cleaning system delivers the best results while protecting the material.

👉 Discover the recommended cleaning system for outdoor terracotta and clay surfaces

When This Treatment Is Recommended

Use this cleaning system when terracotta and clay surfaces show:

• widespread dark staining
• surface biological deposits
• algae, mould, moss or lichens within pores and joints
• slippery or visibly deteriorated surfaces

In particular, this system works extremely well for removing moss and lichens from terracotta, even in very damp or heavily shaded environments.

Surfaces and Application Areas

This system is suitable for:

• outdoor terracotta floors
• clay and terracotta surfaces
• covered patios and loggias
• walkways and courtyards
• historic or high-value outdoor surfaces

It is especially effective in areas exposed to standing moisture and prolonged shade.

The Problem of Biological Build-Up on Terracotta

Terracotta and clay are naturally porous materials.
Over time, the presence of algae, mould and lichens on terracotta causes darkening, slippery surfaces and the gradual deterioration of outdoor flooring, leading to:

• persistent black stains
• aesthetic deterioration
• increased moisture retention
• loss of surface uniformity

Improper cleaning methods or the use of aggressive products may damage both the material and the surrounding environment.

Treatment Principles

For this reason, removing biological deposits from terracotta should not be limited to surface cleaning alone. Instead, the treatment must:

• act deeply on microorganisms
• promote the detachment of biological deposits
• allow controlled mechanical removal
• respect the porous and delicate nature of the material

The removal of moss and lichens from terracotta should always be carried out using a system compatible with the material, avoiding aggressive and short-lived solutions.

Recommended Cleaning System for Terracotta and Clay

Step 1 – Stain Removal and Sanitising Treatment

Application of ALGANET®, a highly effective stain-removing cleaner designed to eliminate algae, moss, mould and lichens.

The treatment is carried out using stiff brushes, BROWN BUFFER PAD or BROWN DISC, which help provide the mechanical action required to detach the most stubborn biological deposits.

ALGANET® remains effective even at low temperatures and can be applied repeatedly in cases of persistent contamination without damaging terracotta.

Step 2 – Rinsing and Final Cleaning

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

• removing residues of degraded dirt
• eliminating any remaining treatment residues
• restoring a uniform appearance to the surface

In addition, use stiff brushes, BROWN BUFFER PAD or BROWN DISC to complete the cleaning process more effectively and improve the final result.

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

Treatment Result

Once the treatment is complete, terracotta and clay surfaces are:

• free from algae, moss, mould and lichens
• more visually uniform
• less slippery
• enhanced in their natural appearance
• ready for any subsequent protective treatments

Frequency of Use

This system is recommended for deep restorative cleaning, to be carried out as needed or whenever new biological contamination appears.

Furthermore, in particularly damp or shaded environments, the treatment can be repeated over time without altering terracotta and clay surfaces.