Any Negative Effects of Green Moss Growing on Roof Tile Besides Appearance?

Written by janet beal
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Any Negative Effects of Green Moss Growing on Roof Tile Besides Appearance?
Moss can affect the quality and performance of your roof. (Jupiterimages/Comstock/Getty Images)

Unfortunately, while moss on the roof may give your house an old country cottage feel, current opinion asserts that it does more harm than good to your roof and your house. Moss growing on your roof interferes with water runoff and therefore enhances rot; loosens shingles and may result in their loss; can signal larger water-related problems; and may get worse if handled with the wrong do-it-yourself measures.

Interferes With Water Runoff

Moss as a living plant uses water to survive. On your roof, moss will retain water that shingles and a slope are supposed to deflect into runoff. Damage can be worse on untreated wood shakes but can also affect the longevity of compound shingles. Long-term exposure to the moisture held by moss promotes rot and decay of roofing materials of all kinds.

Loosens Shingles

Moss grows. Anyone who has ever seen dandelions in sidewalk cracks or wildflowers poking through blacktop knows that the force of growing plants is almost unimaginable. In its attempt to survive and spread, moss will seek out crevices and damp spots in which to establish roots. Green sprouts will push wood shakes apart at their seams and even lift slate tiles by their edges. Eventually, moss can loosen tiles, slates, shingles and shakes until they begin to fall.

Signals Larger Problems

The sight of persistent mossy patches on your roof should raise questions about other possibly troublesome water issues. Large trees may need pruning to improve air circulation and light, both of which can affect the condition of house siding as well as roofing material. Seemingly minor but chronic damp patches in your yard can come from poorly-directed runoff. Examine gutters and leaders to make certain they are clearing water adequately from the roof and moving it far enough from the foundation. Examine hard-to-access attics and storage areas; a leakage problem may have already started.

Gets Worse With DIY

Every site that advises on moss removal contains a reminder that roofs are slippery and dangerous even when dry. Removal and prevention strategies vary: chlorine versus oxygen bleach; copper versus zinc flashing; pressure wash versus nonpressure wash. Look hard at your DIY abilities; if hanging two mirrors and a towel rack took real time last weekend, get some help.

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