How to repaint an exterior facade infested with mold?

PROBLEM: External facade infested with mold

The formation of molds and algae on the external walls of buildings is manifested by a series of concomitant factors.

Both molds and algae require the presence of moisture on the wall for prolonged periods.

This condition can occur, for example, as a result of long periods of continuous rain or in the case of surface condensation due to high atmospheric humidity associated with daily temperature fluctuations.

In addition to water, algae require light and trace elements, while molds require organic material that can come from various sources: dust carried by the wind, bird droppings, dirt resulting from wall seepage, atmospheric particles carried by rainwater, and finally, from the finishes present such as paints or coatings.

As can be seen, most of the listed events are beyond control.

In addition to those mentioned, there is the proximity of potential sources of contamination such as animal farms, the proximity of trees to walls, the adjacency to other neighboring houses that are already infested, etc.

Errors in design that facilitate condensation or water stagnation also sometimes contribute to these issues.

The causes of mold appearance, therefore, go far beyond the product used to decorate the wall, and it is necessary to have knowledge of them in order to understand the limitations of the interventions proposed in this regard.

That being said, in order to make the occurrence of mold less likely, the correct choice of products and the correct execution of the application cycle are still essential.

THE MAIN FACTORS

The main factors that influence the growth and spread of all microorganisms (in our case molds and algae) are the following: water, temperature, and nutrients.

Water

In the absence of water, life cannot develop; consequently, there is no possibility for the growth of molds, fungi, and algae in substrates, whether they are plaster, wood, paintings, or coatings of any nature.

Temperature

The reproduction speed of microorganisms is influenced by temperature. Low temperatures slow it down, while the range between +20°C and +35°C provides the optimal conditions for rapid growth.

Nutrients

In addition to water, microorganisms require nutrients such as nitrogen, carbon, phosphorus, etc. These substances can be found in different substrates or can deposit with dirt or atmospheric particles.