Removing Algae from the Facade of Your House

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How to do it Properly

You know those houses or condos where you see darker patches with a square pattern like in the picture below?

That is mold going on the exterior walls, but fear not – it can be remedied!


Investigating the Problem

Mold on the exterior walls of your home can have several causes:

  • Lack of direct sunlight:
  • Mold doesn’t grow well in direct sunlight, so if shaded by natural barriers, such as trees, or other buildings, or if the wall of your house is north-facing, you may encounter problems with mold.
  • Water leak or increased dampness:
  • If there is a broken pipe in the wall and, thus, a water leak, it creates a favorable environment for fungal growth.
  • The building is located in a humid environment or has been built with materials not suitable for its location.

The problem with mold, in addition to the possible aesthetic concerns, is that once the fungus has settled on the wall, it can make its way under the paint. As a result, the paint will crack and cause water to stagnate between the paint layer and the wall. In short, the problem grows as then the paint will dissolve, and the masonry will corrode.

Although, there is a simple and economical solution. Many fear the costs that come with repainting the walls to seal everything up again. However, that should not be a concern at all. Depending on how widespread the mold is on the walls, you can decide whether to do the following steps yourself or decide to call a special company.

1. Tester section

Usually, you can ask companies that specialize in this type of mold removal to complete a test section, and for free. Therefore, you can see the result before you commit. Plus, you can ask questions about the process as well as the cost of cleaning.

2. Pretreatment

Once you have decided to move on with this process, it’s important to make sure that the mold won’t regrow after some time. So, you must first remove the mold that is already there. To do this, the wall must be decontaminated first. As such, the mold on the wall will have to be killed with a special biocide. Luckily, the products used make it possible to kill the spores in just 24 hours.

After this, comes the scraping step of the pretreatment. It is important not to scrape the mold before killing it, as the spores could disperse and proliferate in other areas of your home. For the best results, apply the biocide at least a couple of times.

3. Rinse phase

After sterilizing the infested areas, equip yourself with mid-arm length plastic gloves, goggles, and an N-95 respirator. For mild cases, you can rinse by scrubbing with warm water and detergent. After carefully washing the affected areas, make sure they are completely clean and dry before painting or caulking.

If you sought the help of professional cleaners to sort out the mold problem, then they will rinse off the biocide for you. In this case, the wall will be rinsed off gently with a telescopic lance and water.

4. Applying the fixative primer

To continue, a coat of primer should be applied, so that the paint sets on the wall and over time does not form cracks, splits, or detachments. The fixative primer ensures excellent breathability, which is essential to prevent future fungal growth. This also allows for adhesion between the wall and the final finish.

5. Use a mold-resistant, isolating paint

Now for the final step of your anti-mold procedure: the paint.

Be aware that not all paints are the same! In fact, there are paints, known as thermo-paints, that are specifically designed to prevent the formation of condensation mold. Thermo-paints act against the formation of spores and fungi because they are designed with anti-condensation and breathable properties.

To be more precise, their design incorporates hollow glass microspheres. These are able to attenuate the difference in surface temperature between the coldest points of your room. This eliminates the possibility of mold finding a suitable surface for its proliferation.

To be clear, it is not a thermal insulator, but rather a corrective action of surface irradiation capacity. The presence of active biocides also guarantees a preventive effect against bacterial aggression on the walls.

The color of the thermo-painting is white, and we do not recommend adding pigment to it, because this could alter the homogeneity. Though, after the applying 2 coats of the thermos-paint, you can eventually apply a third coat of paint in any color you prefer.


As always, we advise you to consult an expert before you start experimenting and trying to solve any mold issue yourself. The products used by companies for mold removal are eco-friendly and ideal for green buildings. This respects your health and that of the environment while helping to eliminate the problem altogether. Though, hopefully, we have given you new direction to do with any mold concerns on the exterior of your home.

If you think that your problem is different from what we have discussed in this article, contact us and send a description with photographs. We will find the best solution to your problem. By the way: If you do not want to contaminate the environment and risk intoxications yourself, you should consider sustainable facade cleaning.

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