Cleaning Patio Tiles: How To Remove Moss And Algae

If dense moss colonizes patio slabs, the joy of the popular outdoor seating area is very much dimmed. Neither wood, nor stone are spared from the green coating. Since the slabs become slippery at the same time and thus dangerous with every step, there is an immediate need for action. Experienced amateur gardeners do not let themselves get gray hairs because of it, because there are effective ways and means to become master of the plague. Gone are the days of laborious combat in a stooped position or even on your knees. Find out below how you can remove moss and algae from your terrace without having to resort to chemicals.

Mechanical aids

  • Joint brush/grout scraper
  • Flaming device
  • Steam device
  • High pressure cleaner
  • Infrared burner
  • Hot water foam device

Home remedy

  • Mixture of soda, starch and potassium permanganate
  • Coca-Cola
  • Soft soap and ingredients
  • Hydrogen peroxide
  • Commercial vinegar cleaner
  • Vinegar and salt are prohibited by law
  • Preventive measures

Mechanical aids on stone patio slabs

One of the most common building materials for terraces is stone in any form. From simple exposed aggregate concrete to high-quality natural stone, creative do-it-yourselfers lay the most diverse variants. Moss and algae tend to care less about the quality, because they thrive particularly lushly here, seeming to just claw their way into the joints. Those who consciously decide against using a chemical mace here will find effective support in the following devices and tools.

Joint brush/grout scraper

This method of moss removal does not work without a certain amount of force. It compensates for this fact with a completely environmentally friendly mode of action at a very low financial cost. A grout scraper cleans even the smallest gaps with its curved steel blade. No less efficient acts the joint brush with its hard bristles made of metal or plastic. Larger areas, which are green with moss and algae, treat more quickly with wide brushes.

Water steam device

Heat of all kinds removes moss and algae from patio slabs formed of stone. The effectiveness is based on the thermal effect, which causes the protein cells to burst. The heat blast is also produced by a steam device. Unlike a hot water jet, which could wash out the grout, the boiling hot steam specifically destroys moss and algae mats. Puny remnants are simply swept away. The precaution of a trial in an inconspicuous place is also recommended here.

High pressure cleaner

In principle, the high-pressure cleaner works in the same way as the steam cleaner. The cleaning effect on the stone slabs can be considered disproportionately higher than when using steam. Not only moss and algae must give way, but all deposits that have accumulated. A disadvantage is that joint material is washed out. Experienced hobby gardeners use special Dansand or polymer sand for repointing. These types of sand have a marked inhibitory effect on any weeds; thus also on moss and algae on patio slabs.

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Flaming device

Here, a jet of fire up to 2,000 degrees shoots out of the gas-powered device. Moss and algae are destroyed in seconds. A few hours after the treatment, the unwanted coating comes off easily and can be swept up. Since not every stone quality tolerates this rigorous cleaning method, a prior test on an inconspicuous spot is advisable. The device should not be used along the transition to the lawn or bed, because it radiates heat up to there.

Infrared burner

Instead of using fire, as with a flaming device, the infrared burner uses heat radiation from a glowing grid to combat moss and algae. While root and seed weeds are only singed in this case, to reappear after a short time, moss and algae do not let themselves be seen for the rest of the season. In this case, however, you will not be able to avoid thorough sweeping.

Hot water foam device for large terraces

Cleaning Patio Tiles: How To Remove Moss And Algae

An innovation in the ecological removal of moss and algae is becoming more and more widespread. It combines hot water and a natural foam made of 100 percent plant sugar, based on coconuts and corn. Spread on the patio slabs, the mix holds the heat there for a whopping 2 minutes. This time is sufficient to completely destroy the cell structures. After another 5 minutes, the foam has dissolved. Now it takes another 2 to 3 days until the green coating turns brown to sweep it with a broom. The use of pesticides is therefore unnecessary. The smallest device so far is only profitable from a terrace area of 200 square meters. It will be interesting to see whether suppliers will soon be able to offer suitable hot-water foam devices for private use.

Thermal devices for wooden terraces unsuitable

Although moss and algae find first-class growth conditions on wooden patio slabs, you should refrain from hastily reaching for a high-pressure cleaner, steam cleaner or even a flamer. The wood pores would take considerable damage by the heat effect. The grain will crack. Splinters form, making it almost impossible to walk barefoot.

If you are striving to remove moss and algae from a wooden deck, you have a whole arsenal of proven home remedies and environmentally friendly methods at your disposal instead. The procedures explained below eliminate the green patina from stone and wood alike.

Home remedies against moss on patio slabs

Moss and algae thrive wherever nature provides them with suitable growing conditions. They do not take into account the construction plans and wishes of people. The more humid the situation, the more intensively the green plaque spreads on the terrace slabs. Those who do not like or cannot resort to mechanical means for its elimination, use one or more of the following home remedies.

Soda and cornstarch

The ingredients for an environmentally friendly and at the same time powerful moss and algae remover you probably already have in the house. What you need is washing soda, i.e. sodium carbonate, and cornstarch. Here’s how you can easily make the home remedy yourself:

  • Mix 3-4 tablespoons of Mondamin or Gustin in lukewarm water.
  • Heat 5 liters of water in a pot
  • Add 100 grams of soda

Finally, stir in the dissolved cornstarch until you get a paste with the consistency of wallpaper paste. While the mixture is still warm, apply it thickly to the patio tiles with a tassel. Leave the mixture to soak in for 4 to 5 hours. Now scrub your patio clean and rinse thoroughly.
If you have stone patio slabs from which you want to remove moss and algae, you can increase the efficiency of the home remedy. Add to the mixture a dash of potassium permanganate from the pharmacy. Dilute 15 grams of the powder in 10 liters of water beforehand. When applying, make sure to wear gloves, goggles and insensitive clothing, because potassium permanganate oxidizes strongly. On light-colored natural stone, the strongly staining home remedy should not be used without a prior test run.

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The phosphoric acid in the popular soft drink is said to be very bad for moss. At the same time, no discoloration is to be feared, nor is the joint material between the patio slabs attacked. Only in undiluted application results are to be expected. In the absence of credible suitability tests, a self-experiment at least can not hurt. It should be borne in mind, however, that the high sugar content could attract droves of ants and other insects.

Agents based on soft soap

Environmentally conscious hobby gardeners are familiar with soft soap in some respects. For example, this biologically harmless substance is often a component of pesticides against pests and plant diseases. Curd soap is also excellent for removing moss and algae from patio slabs. If you add a few more ingredients, you can create a natural care product that you can make yourself without much effort and at low cost:

Ingredients for 10 liters of detergent:

  • 100 ml liquid soft soap
  • 10 liters of sparkling hot water
  • 60 g washing soda
  • 60 ml glycerine
  • 120 g stain remover

All ingredients are mixed in a sufficiently large container. Even if you are insensitive to the various ingredients of the solution, you should not do without rubber gloves. The synergistic effects cause a sometimes significant increase in effectiveness, so it could quickly cause unwanted irritation of the skin. Apply the agent to the mossy patio slabs immediately after preparation. The cleaning-active oxygen that is formed in this process is only available for a very limited period of time. Ideally, apply the cleaning agent with a sponge and let it soak in for about 20 minutes. Then scrub the surface and rinse thoroughly with clean water. With proper application, you should be looking at a clean patio for half a year as a result. The reason for this is the remaining glycerin, which prevents renewed moss and algae growth for at least a few months.

Hydrogen peroxide

This oxidizing agent offers a wide range of uses. These include removing moss and algae from patio slabs. Applied pure to the green patina, the agent immediately attacks the tiny fungi of algae and moss. They quickly dry out and die to be swept away.

Leave vinegar, salt and lemon juice on the shelf

It is a relic of old times and still persists. We are talking about the so-called home remedy vinegar and salt as an effective means of controlling weeds, moss and algae. The fact is that the combination of active ingredients has been prohibited by law since 2012, especially on sealed surfaces. For good reason, the violation is punishable by a fine of up to 50,000 euros, because the consequences for the environment and health are incalculable. The pungent mixture seeps into the groundwater, killing all the microorganisms in the soil along the way. In the long run, nature would be thrown into an imbalance that would be life-threatening for humans and animals.

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In addition, the resulting acid causes considerable damage to patio slabs, far outweighing the cleansing effect. Stone slabs in particular subsequently exhibit brown acid stains that can no longer be removed. In addition, the joint material dissolves with further unpleasant consequences.

However, there is nothing wrong with using commercial vinegar cleaner to clean patio slabs at an early stage of moss infestation.

Preventive measures

Probably the most economical way in the fight against moss and algae on a terrace is based on a resounding prophylaxis. This begins with the selection of the material from which the panels are made. The smoother the surface, the less the tiny plants can gain a foothold. In addition, the installation technique plays an important role. Where moisture can accumulate, moss and algae are not far.

Prefer patio slabs made of granite, marble or ceramics.
Glaze wooden slabs naturally from the start with beeswax or linseed oil
Always lay the surface with a slight slope to avoid waterlogging
For grouting stone slabs use Dansand or polymer sand
If you prefer a wooden terrace, it is advisable to use WPC boards. The abbreviation stands for Wood-Plastic-Composites, i.e. a wood-plastic combination. A variety of advantageous attributes speak for this innovation, which is much talked about among professionals, as well as DIY enthusiasts. The surface dries particularly quickly and leaves no chance for algae or moss. Without the use of wood preservatives or special oils, lukewarm water is sufficient for cleaning.


In order to completely remove moss from patio slabs, it is not necessary to use environmentally harmful chemical-based products. With vehemence, scientists as well as dedicated hobby gardeners have compiled an extensive collection of efficient methods to remove moss and algae from a terrace. The spectrum ranges from mechanical aids to effective home remedies to resounding prophylactics. As if that were not enough, new findings are constantly being added, so it is worthwhile for interested homeowners to regularly update themselves.


  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.

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