The expert advice

SOS mold external floors: How to eliminate mold, algae and lichens

19 June 2024

How beautiful are the external complements that adorn our home? Walls, lanes, terraces, planters, cotto, travertine and stone floors are truly one more beautiful than the other. But, all afflicted by the same problem: the serious difficulty, let’s face it, of keeping them always beautiful, clean and decent. Have you ever found unsightly black stains on the external cotto, or seen lichens sprouting from the stones of the driveway? These are very common problems. Algae, mould and moss are weeds that lurk inside the stone and can penetrate deeply into the porosity of the material. For this reason they often recur, despite the deep cleaning of the surfaces. Let’s find out how to remove mold from the outdoor floors!

Why do we create mold on external floors?

Every surface can be the target of these treacherous substances, not just in wetlands. But why do they form? Moulds are fungi, bacteria and spores that manifest themselves as opaque spots on the surface and slowly tend to expand and compact becoming real very dark incrustations.
The external surfaces, being those more exposed to the effects of atmospheric agents, are consequently those more exposed to the attack of these fungi. The rain, the humidity, the scarce presence of sun or wind, contribute negatively to the spontaneous formation of these annoying patinas. In fact, the presence of mosses, algae and lichens is much more frequent on the surfaces to the north, which are little exposed to the sun.

come-pulire-pavimenti-in-pietra-esterni clean outdoor stone floors

How to remove mold from the external floor

To eliminate mould and restore the beauty of our external surface and remove mould from the external floor it is possible to follow two paths: depending on the type and quantity of scale and black spots we can choose more artisanal methods, that will certainly not be able to remove mold or moss infiltration, or more professional methods, which involve the use of specific products. In any case, we always keep in mind that our most important ally is elbow grease! In fact, it is necessary to rub a lot to eliminate algae and lichens that lurk deep in our outer stones.

Let’s finally find out how to remove black stains from external cotto or natural stone floors!

External floor cleaning with ALGANET

Pulizia pavimenti esterni ALGANET | MARBEC

ALGANET is a powder cleaner specifically for deep cleaning of exterior surfaces made of stone, such as porcelain tiles, ceramic, cotto, marble, stone and terrazzo. It helps to remove blackening left by microorganisms (e.g. algae residues, mosses and lichens), leaf and flower residues, animal excrement, urine, etc. It can also be applied to treated surfaces and has a deeper and more effective action over time than sodium hypochlorite. It can also be used for cleaning curtains and PVC tarpaulins and other plastic material outdoors, and is effective even at low temperatures. Once dry, it is no longer dangerous for vegetation and can be, therefore, rinsed thoroughly with water. It can be applied several times on very dirty surfaces and in the presence of lichens that are difficult to remove, without damaging stone materials.

Just dissolve 800gr of ALGANET in 10 liters of water, mixing for a few minutes. The solution thus obtained must be used within 3-4 hours, otherwise it will lose its cleaning action. It can be applied with a brush or with a cloth or a broom. At this point it is advisable to rub the product with a hard brush or an abrasive pad, such as the BROWN BUFFER. The product is then left to dry and then rinsed with plenty of water.

BROWN BUFFER is the ideal tool for deep washing of external surfaces, in combination with ALGANET. In fact, the BUFFER is very abrasive and its fibers can remove substances that are deep in the porosity of the material. Another equally useful tool is the BROWN DISC, in case you want to clean the surface with a single-brush machine.

Watch the ALGANET application video tutorial

Protective treatments and sealing of external floors

Neutral effect water repellent treatment with TIM

TIM is a protective for the water-repellent and stain-resistant treatment of absorbent stone materials. This product is ideal for cotto, stone or concrete floors. TIM is a water-based product, odorless, not dangerous and easy to use, ideal for protecting both internal and external surfaces. This protective is commonly used as a basis for wax treatments, since it eliminates or drastically reduces the absorption of water, liquids, fatty substances and oils in the material, counteracting the formation of saline efflorescence, scabs, patinas and algae. TIM has a high chemical inertia and resistance to atmospheric agents and trampling, without creating film on the surface or altering the appearance of the material. In addition, it maintains the original permeability to water vapor, ensuring breathability. Apply TIM on clean, dry, untreated absorbent surfaces. Shake the product before use and distribute it evenly with a brush, a microfiber cloth, a sponge or a spreading fleece, wetting the surface evenly. The drying time is 8-12 hours depending on the ventilation, and it is advisable to avoid that the treated surfaces are wet from the rain for at least 12 hours.

Water-repellent wet treatment with TON PLUS

Also TON PLUS is a water repellent anti stain protective, specific for absorbent stone materials such as cotto, stone and terrazzo. What differentiates it from TIM is the final effect of the treatment: in fact, with this product you get a wet effect, while with TIM you get a neutral effect. TON PLUS is a water-based product, odorless, not dangerous and easy to use, suitable for indoor and outdoor surfaces. It forms a chemical barrier against rising moisture and stain, giving a marked wet effect lasting without creating film and without altering the appearance of the material. It eliminates or drastically reduces the absorption of water, liquids, fatty substances and oils, counteracting the formation of saline efflorescence, crusts, patinas and algae. Commonly used as a base for wax treatments, it offers high chemical inertia and resistance to atmospheric agents and trampling, maintaining the original permeability to water vapor and ensuring the breathability of the material. TON PLUS is applied by applying it on the surface with a brush or with a microfiber cloth, avoiding accumulations of product. Avoid that newly treated surfaces are exposed to the weather during the drying phase 12-24 hours. Then, after 4-6 hours you can apply a finish type PAV05.

Final protection layer with PAV05

PAV05 is a protective wax with an anti-dirt, anti-degradation finish for cotto, stones and terrazzo. PAV05 is a water-based product, odorless, not dangerous and easy to use, which increases the protection of materials treated with water repellents, such as TIM and TON PLUS, extending their life. It offers excellent anti-dirty, anti-degradation and weather resistant properties, drastically reducing algae growth on surfaces. It enhances the coloring of the material without forming a thick film, maintaining a good vapor permeability. It makes the surfaces easier and faster to clean, preserving them over time with ordinary cleaning using the ECOMARBEC detergent and applying PAV05 once or twice a year. This product is resistant to weathering and trampling, gives a little tone to the material and prevents the formation of mold. PAV05 is distributed with a spreading fleece or a soft cloth. It should be spread in a thin layer, wetting the surface evenly and without making excesses. It dries quickly, generally in 2-3 hours.

Periodic maintenance of external floors

To avoid the proliferation of lichens and the reformation of stains, it is advisable to carry out two annual cleaning with ALGANET: one in autumn and one in spring. This type of cleaning is particularly useful for those places that are little exposed to the sun and wind, which therefore are in the most favorable conditions for the proliferation of fungi and bacteria. As for the routine cleaning of external floors, the ideal product is ECOMARBEC, a concentrated detergent for cleaning stone materials. This product does not contain caustic soda, ammonia, perfumes, dyes or solvents and for this reason it is not aggressive towards the environment or towards those who use it. ECOMARBEC works by dissolving fatty substances and making them easily removable. In addition, it has a low foaming and can therefore be used for mechanical washing with scrubber drier or pressure washer.

The products covered in the article
  • 23.70€


    Concentrated stain remover in powder specifically for the deep cleaning of external stone floors. It cleans and helps to remove algae, moss, and other encrustations of organic origin from surfaces.

  • 5.32€


    Sponge with strong abrasive properties, for strong descaling and de-waxing of stone materials.

  • 9.06€


    Detergent for the ordinary and/or extraordinary cleaning of all floors. It cleans, degreases and sanitizes surfaces and does not attack materials. Biodegradable, does not contain perfumes and hypoallergenic.

  • 31.67€


    Protective product for the water-repellent and anti-stain treatment of absorbent stone materials. It does not create a film, is breathable and does not alter the appearance of the material.

  • 15.80€


    Protective finishing anti-dirt, anti-degradation wax resistant to atmospheric agents and trampling for cotto, stones and terrazo.

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