Why Do Roofs Turn Green?

Algae and moss can grow on roofs and lead to problems if not properly maintained.

It happens after a wet winter. You know the green or brownish stuff growing on your roof. It can look really horrible and in some cases create big problems with your roof if not taken care of.

Why do roofs turn green?

I have found in Sacramento, California, that moss, algae and lichen have more of a chance to grow on the north side of a roof. We live in the northern hemisphere on earth and because of this, our steeper roofs don’t see enough of the sun to dry out.

These areas of the roof stay damp and wet which helps in the spreading of that ugly green stuff. Algae is a plant and loves damp shaded areas like roofs that are shaded by a large tree or are covered with debris.

Algae can grow on any type of roof, so a regular roof maintenance program is advised. Using a licensed roofing contractor to clean off the algae and do any repairs that may be needed would be a good idea. I like seeing this done right before December. This means the leaves have all fallen and your roof will be all cleaned of debris and ready for the winter.

How to stop algae and discoloration on my roof

This will help with a new roof but if you have a roof that is not ready for replacement having zinc strips installed can reduce the growth of algae infested areas. The roof installed zinc strips have a reaction when mixed with rainwater. The zinc precipitates a mixture of fluid that organic materials do not like and thus helps stop those green roofs. Ask a licensed roofing contractor for advice and installation. The photo to the left is a heavy shake roof I contracted to do a few years back. The customer had problems with moss and algae and requested copper on all the ridge to control the algae. A return back to this roof is proof for me that it works and I have used this same system on more than just this house.

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