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Green Growth Removal & Prevention

Updated: Feb 13

Understanding Algae and other bio contaminations

The three main bio growths you will find in and on masonry are Algae, Mould and Lichen. These common bio growths on masonry surfaces not only compromise the appearance but also can potentially lead to structural damage if left untreated. Regular cleaning and maintenance are essential to prevent their growth and preserve the integrity of the masonry.


The Red Algae grows slowly on vertical walls in mild climates, usually on a shady wall. Interestingly, it grows on concrete and cement and rarely on any other materials. It spreads from spores in he air.

The Green Algae is similar to red algae, it doesn’t enjoy direct sun-light, it prefers a shady wall, but unlike the red algae, this needs a regular supply of water. You will find it where water is dripping from defective rainwater gutters, pipes or flashings. If you look at the image you will see that its is located near the ledges at the top of the wall. Green Algae is a clear indicator that walls are being saturated and there is a problem that needs to be investigated.

Black Algae are single-celled organisms that grow in large colonies. They contain chlorophyll like other algae, but they also contain compounds that mask the green color. It forms in cracks and crevices on pool surfaces (especially plaster finishes) and can grow somewhat protected from the surrounding environment due to the formation of a protective layer on the outside of the cell. This makes black algae more difficult to treat and it is somewhat resistant to normal chlorine levels.


Mould is a type of fungus that thrives in damp, humid environments. It appears as fuzzy or powdery growth, typically black, green, or white in color, and can spread rapidly on various surfaces, including masonry. Mould derives nutrients from organic matter present in its environment, such as dirt, dust, or residual organic materials. It poses health risks as mould spores can become airborne and lead to respiratory issues when inhaled. Additionally, mould can cause structural damage if left unchecked, making regular cleaning and maintenance crucial for preventing its growth and preserving the integrity of masonry surfaces.


Lichen is a symbiotic organism consisting of fungi and algae or cyanobacteria. It can be found most commonly in areas with minimal pollution and can tolerate harsh environmental conditions. Lichen often grows on various surfaces, including rocks, trees, and masonry. It forms a crust-like or leafy structure and can appear in various colors, including green, gray, yellow, or orange, depending on the species and environmental factors. While lichen can thrive in diverse habitats, it is frequently found in regions with clean air and limited human disturbance.

Dry Rot Masonry (Bonus)

Dry rot in masonry occurs when certain types of fungi, such as Serpula lacrymans, infest and deteriorate wooden components within masonry structures. These fungi thrive in damp, poorly ventilated environments, often caused by water ingress through cracks or leaks in the masonry. Dry rot can spread rapidly, causing decay and weakening of wooden elements like beams, joists, and framing embedded in the masonry.

Dry rot is dangerous because it can compromise the structural integrity of the building. As the fungi consume the cellulose in wood, they weaken its structure, leading to potential collapse or significant damage if left untreated. Additionally, dry rot can spread to other areas of the building, affecting more structural elements and increasing the extent of damage.

To mitigate the dangers of dry rot in masonry, it's essential to address the underlying moisture issues causing its growth and to promptly remove and replace any affected wood. Regular inspections and maintenance of masonry structures can help detect and address dry rot before it causes significant harm.

Remmers Adolit M Liquid

(Masonry Dry Rot Solution)

Liquid preservative concentrate for preventing dry rot in masonry work

■ Porous, mineral building materials

■ Sheltered masonry (not exposed to weathering)

■ Inhibiting agent for dry rot

Green Growth Removal Solutions:

Algae Rem

1 component water based Mildews, Algae and Spores Remover

■ Kills all living organisms, mildews, algae, and spores on masonry surfaces.

■ Does not clean dirty masonry but effectively removes undesirable and unsightly growths.

■ Leaves no algaecidal agents in the masonry after sterilizing the surface.


Bactericidal, fungicidal and algicidal combination product for cleaning and priming building materials with and at risk of green discolouration

■ Preventive protection against green discolouration

Removing biological contamination from mineral substrates, insulation systems, and coatings.

■ Excellent long-term effect

Contec Surface Reviver

A high-performance cleaner designed to remove organic and microbiological contaminants from porous surfaces such as stone, cement, tarmac etc

■ High-performance cleaner for removing organic and microbiological contaminants

■ Suitable for driveways, patios, paths, walkways, roofs, decking etc.

■ Designed to clean, disinfect and revive

Algae Prevention:

What can we do to prevent algae growth in the future?

The best way to prevent algae growth is to put down a biocide primer like BFA or Algae Rem that will sit on the surface and prevent against algae growth for some time.

Another effective method is to stop water from soaking into the surface completely using a waterproofing system like Remmers Color LA an algae inhibiting paint that is extremely waterproof, or Impregnation Sealers, a wide range of impregnation sealers for masonry surfaces.

These sealers create a protective barrier that repels water, preventing moisture from penetrating the substrate and creating conditions favorable for algae growth. See the products below for more details on this essential step in maintaining clean and algae-free surfaces.

Color LA

"True" silicone resin paint with film preservative for surfaces at risk of infestation with algae or fungi. Façade paints not only serve the colour design of the building but also its protection. The main task is to keep moisture and therefore contaminants away from the building and at the same time maintaining an adequate level of breathability. These can be achieved with different paint types.

Impregnation & Sealers

Impregnations penetrate into the surface to ensure that there is excellent protection and permeability (breathability). It is important for renders like lime to have breathable protection so it does not affect the natural operation of the masonry or render.

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