If you've got a shingle roof, you might have noticed algae or moss growth, which can raise some questions about the impact they have on your roof's health and longevity. Let's break it down and address any concerns you might have.
Starting with algae – you might see it in green patches or as black streaks (often mistaken for mildew) on your roof. The good news is that algae presence is mostly a cosmetic issue. It may not be pleasant to look at, but it's not going to cause your roof to fail prematurely. If you can't stand the sight, however, there are safe cleaning solutions available that can help you get rid of this unwanted guest without damaging your shingles or tiles.
Meanwhile, a traditional method to prevent algae growth is through the use of zinc or copper. These metals are key ingredients in some shingles, and they naturally inhibit algae and mildew. As rainwater flows over zinc or copper strips installed on your roof, it creates a protective barrier that disorders algae growth. This can be an effective way to maintain your roof's aesthetic.
Moss, however, is a different story. It tends to secure itself quite firmly to shingles. Attempting to forcefully remove moss can have detrimental effects, such as stripping off the protective granules on your shingles, which leaves the underlying asphalt exposed and vulnerable. Different from algae, moss typically thrives in less sunny areas of your roof. But even though it's slow-growing, you might worry about potential damage.
The reality is, even though moss isn't exactly a sight for sore eyes, it's better to leave it alone. The chances of moss developing on your roof without the presence of a large tree nearby are slim. If you do have a big tree shading your roof, chances are it's part of the reason the moss grew in the first place. And, as much as the moss might bother you aesthetically, it isn't harming your roof's ability to shed water. It sits atop the granules which, in turn, protect the waterproofing asphalt and the fiberglass mat underneath.
In the end, understand that while moss and algae might not be adding to the curb appeal, they're not necessarily your roof's enemies. Removing them – especially moss – could prove more harmful than leaving it be. So when deciding whether to go after that moss, you might also need to consider the trade-offs between keeping the tree that's shading and protecting your roof or keeping your roof moss-free.