Why Is There Green Moss On My Roof

Moisture and organic debris.

Why is there green moss on my roof.

Moss doesn t always mean you re destined for a whole new roof nor does it mean your home has water or moisture damage. Moss is a non vascular plant that absorbs water through its leaves instead of roots. If there are large trees near the home that shade parts of the roof moss can grow in abundance as there is a lack of direct sunlight. Left untreated the clumpy greenery can cause virtually any roofing material to degrade most commonly wood and asphalt but also metal clay and concrete and thus drastically shorten its lifespan.

Sunlight reheats the roof evaporating moisture. The more water and the more debris the greater the chance of moss growth. The typical cause is twofold. Another critical factor is the amount of shade your roof receives.

Lack of sunlight heat and lack of air venting underneath the roof deck. Roof shingles are the perfect place for moss and other algae to grow as this part of your home receives the most rainfall and has higher levels of humidity making conditions perfect for moss to thrive. Most of the time roofs shed water from the outside well enough that moss buildup isn t caused by weathering. Moss commonly thrives in environments that are damp and shaded.

Moss on a roof begins with a thin dusting of green that you may notice only from low angles. Moss acts like a sponge absorbing large amounts of moisture and resulting in your roof being constantly wet. Because moss or lichens growing on a roof surface will hold moisture on the roof longer than other areas these growths can reduce the life of the roof covering. If you have moss on your roof it s likely because your roof is shaded by trees or other structures allowing moisture to linger and moss to grow.

The roots can lift up shingles and constant moisture can lead to bacteria and mold growth. Most roofs will experience moss or lichen growth and small patches of growth are usually not a problem. Moss algae and lichen grow on your roof through a combination of two things. Moss absorbs the moisture from the damp environment and establishes roots on your roof causing the beginning of roof degradation.

This thin layer on the top of the shingles expands and becomes wide thick and mat like. If the moss growth is allowed to develop further it can become a problem for the roof for a number of reasons.