Why Moss is a Roof’s Biggest Enemy

As they are so exposed to the elements, our roofs can suffer from a number of issues that may cause them to deteriorate or become damaged.

From debris impact in high winds, to water ingress due to cracked tiles or shingles, many of us suffer from roofing problems from time to time.

However, one of the biggest threats to our roofs – especially in terms of the lack of attention paid to it – is the growth of moss and other algae, and the multitude of issues that this can cause.

Main Dangers of Moss

First of all, it must be stated that moss in itself is not dangerous. It is free of spores and other poisons that could potentially have an effect on felt, slate, asphalt and other roofing materials, and, in general, its growth is limited enough to not pose a threat to structural elements.

The root cause of all the problems that moss can create is its ability to retain rain water and moisture from the air long after it has evaporated from other surfaces. This presents a number of dangers for most roofing types, as constant exposure to damp conditions will, over time, reduce the structural integrity of the shingles, exposing your home further to wind and precipitation. In extreme cases it can even lead to rot.

These problems are bad enough, but constant dampness leads to mould, which is an altogether more pressing issue. The damage caused by mould is an amplified and accelerated version of that caused by moss alone, and tackling it at its source is the only way to avoid it.

Moss vs. Algae

It’s not just moss that can be found growing on your roof; algae are another constant source of Algae could be thought of as simply a less evolved form of moss, which would suggest that they are less of a threat. This is largely true, however some algae can leave black deposits that discolour your roof tiles, giving the impression that mould has set in.

Algae mostly only grows in pools of standing water, so finding this fungus on your roof could indicate a deeper drainage problem that will need to be addressed immediately. Some roofing types are better equipped to deal with algae, such as copper, which studies have shown to be over 10 times more effective when dealing with growth than zinc.

Getting Rid of Moss

Due to the dangers of moss growth mentioned above, clearing your roof of it as soon as you spot it is the best way to protect your home.

If there is a thick moss colony covering large areas of your roof, first use a stiff brush or broom to knock this free. You can then apply a solution of both bleach and water, or a specialised moss or algae removing formula that can be bought from most DIY and home stores, using low pressure water to wash it off so as not to damage the shingles.

Always remember the health and safety principles involved with climbing around on your roof.

In some situations, having moss on your roof is desirable. Assuming your roof is new and correctly installed, the addition of moss will add insulating properties that could reduce both your bills and carbon emissions. Similarly, both moss and algae help to create a green roof, encouraging biodiversity with plant and animal life.

Posted on 22 April 2014 in Roof Cleaning.

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