Roof tiles are made of porous material, usually clay, which can absorb a certain amount of moisture. Although tiles are generally low maintenance and last longer than asphalt roofs, mildew and mold on moist tiles can prove to be an eyesore.
What Causes Mold?
Moss, mildew and fungus can't grow directly on roofing tiles, because the clay tiles don't provide a food source. Instead, the growth occurs on the thin layer of dirt or debris that can collect on your roof. Moisture trapped within the tiles can speed this growth.
Not every tile roof will be prone to fungal growth. Those that receive little sunlight or are in humid climates are more likely to experience a moss and mildew problem. Often, moss grows on a shady north side, but the south side of the roof remains pristine. Homes near a waterfront, such as a pond or lake, may be more prone to moss and fungus due to higher air moisture.
Does It Cause Damage?
Fortunately, moss and fungus on a tile roof doesn't cause any structural damage. Unlike asphalt roofs, where moss can lift and damage the flimsy shingles, it it only a surface growth on top a sturdy roof tile.
It can cause stains on the roof, but this is only an issue with the roof's appearance and not with the structural integrity of your roof.
Can It Be Removed?
It's possible to completely remove the moss and fungus without damaging your roof, but you will need a professional roofer to do the job. It's never a good idea to walk on a tile roof or attempt to clean it yourself – this can lead to broken tiles and roof leaks.
Your roofer, who is skilled at working on tiles without damaging them, will pressure wash the growth off of the tiles. They typically use a bleach solution, which removes moss, kills the spores and removes most stains. Once the roof is clean, they will coat and seal the roof to help prevent future moss and fungus growth. If the tiles are badly stained, your roofer can also repaint the tiles to disguise the damage.
Prevention is sometimes possible. Trimming back trees to prevent extensive shading can inhibit fungal growth. Your roofer can also install strips of copper flashing, which prevents moss from growing. Finally, a clean roof has less organic debris to feed the fungus, so scheduling a roofer to do a regular roof cleaning in the fall can minimize growth.
For professional help, contact roofing contractors, such as Roof Tech.