The common asphalt shingle roof found on many north American homes is also known as the ’30-year roof’. This is because on average, houses with these setups are the cheapest to make, and last roughly for about 30 years. Yet, this is an approximation based on hearsay at best. The reality is that this type of roof can last around 30 years IF it is maintained properly. What most homeowners do not know of, are the unseen dangers that can uproot, warp, and disintegrate your property if it is not regularly cleaned. Though it sounds contradictory, cleaning (as in soap and water) your shingles is indeed important for your roof. The reason? Microbes.

Roof Moss- What it is, and why it is so destructive

In north America, there are two types of microbes that will secretly destroy your roof: Algae, and a fungus known as Gloeocapsa magma. Both culprits thrive in the wet and humid conditions of Canadian summers, and additionally feast on the material within asphalt shingles. This is because the fungus and algae can break down asphalt into oil and gain nutrients from it, as well as breaking down the limestone that is often used as filler for these types of tiles. The initial result may look like a slightly darker ‘stain’ or discolouration in the tiles that can easily be mistaken for something natural like age, or wetness. The black stain is in fact the beginning of microbe infestation. Once it is obvious that it is a fungal growth, it is often too late.

In terms of damage, it is clear that the microbes habit of consuming the asphalt tiles primary materials will weaken and destroy the tiles. If it does not succeed in doing this, the growths of moss and fungas are known to burrow under roof tiles, and slowly lift them up. This is bad because it opens a chink in the armour of your home by letting rainwater to seep in under the tiles. The consequence of this leads to further damage in the interior of the home in the form of warped wood. Additionally, once tiles have been infected with the moss/ fungus, they lose their ability to reflect sunlight, and thus can hasten the destruction of the entire roof or section of the roof.

Prevention-

While almost impossible to defend against 100%, there are ways to decrease the chances of roof moss from developing in the first place. The first and clearest answer lies in simple maintenance. This is done by hand-removing large chunks of moss/fungus, and then either hand-scrubbing/ power washing the area (always use the low setting, otherwise it may damage the shingles). Typically soap and water can work, as well as bleach. If you want to be certain that not a spore is left behind, then you may use chemicals such as sodium hypochlorite and copper sulfate, which are particularly toxic to these organic growths. The key is to apply and scrub the product on the area, and then rinse from top to bottom- allowing all waste to wash off the roof. Always do research before using these damaging products however, as they can have other unintended effects of the environment or can be a hazard if accidently mixed.

Another pre-emptive technique to use involves building copper or zinc metal plates underneath the roof tiles. While it is an extra expense, copper and zinc are toxic to both the algae and fungus. This will theoretically prevent spores from ever landing successfully, but it is not a guarantee.

Overall, roofs are just another thing which requires maintenance if you want to get the most out of its expected life-time. While your roof may be outside of your direct vision, it shouldn’t be something that is left behind.