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ROOFING INSPECTION & REPAIR
AMERICAN CEMWOOD ROOFING
BEST ROOFING PRACTICES
BUILT UP ROOFS
CATHEDRAL CEILING VENTILATION
CERTIFICATIONS for ROOFING CONTRACTORS
CHIMNEY FLASHING Mistakes & Leaks
COLD WEATHER ROOF TROUBLE
DECKS, ROOFTOP CONSTRUCTION
EPDM, RUBBER, PVC ROOFING
EXTRACTIVE BLEEDING on SHINGLES
FIRE RETARDANT PLYWOOD
FLASHING on BUILDINGS
FLAT ROOF MOISTURE & CONDENSATION
Green House or Solarium Roof Leaks
HEAT TAPES & CABLES on Roofs for Ice Dams
ICE DAM PREVENTION
MASONITE WOODRUF FIBERBOARD ROOFING
NOISE CONTROL for ROOFS
PLASTIC ROOFING TYPES
PVC, EPDM, RUBBER ROOFING
ROOF ARCHITECTURAL STYLES - PHOTO GUIDE
ROOF CLEANING RECOMMENDATIONS
ROOF COLOR RECOMMENDATIONS
ROOF DORMER TYPES - PHOTO GUIDE
ROOF INSPECTION SAFETY & LIMITS
ROOF JOB PROBLEMS, RESOLVING
ROOF LEAK DIAGNOSIS & REPAIR
ROOF NOISE TRANSMISSION
ROOF REPLACEMENT SNAFUs
ROOFING FELT UNDERLAYMENT REQUIREMENTS
ROOFING MATERIALS, Age, Types
ROOFING TILE SHAPES & PROFILES
ROOFING UNDERLAYMENT BEST PRACTICES
SADDLE CONSTRUCTION at CHIMNEYS
SNOW GUARDS & SNOW BRAKES
STANDARDS for ROOFING
STRESS SKIN INSULATED PANELS
TEST LABS - ROOF SHINGLE
TREES & SHRUBS, TRIM OFF BUILDING
TRUSSES, Floor & Roof
UNDERLAYMENT REQUIREMENTS on ROOFS
VENTILATION in BUILDINGS
WALK-ON ROOF SURFACES
WARRANTIES for ROOF SHINGLES
WORKMANSHIP & ROOF DAMAGE
This article describes and provide photographs of lichens growth that occurs on buildings and in nature and we provide advice about handling lichens growth on roofing surfaces. We include links to references useful in the identification of algae, moss, lichens, and mold. Our photo at page top shows moss on an asphalt shingle roof.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
This website tells readers how to identify, evaluate, remove or prevent stains on building surfaces. Also see ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES where we describe not only moss and lichens but black fungal stains on asphalt shingles and on other building surfaces. Also see Lichens on Stone Surfaces. For the diagnosis and cure of other building stains, see STAIN DIAGNOSIS on BUILDING EXTERIORS and STAIN DIAGNOSIS on BUILDING INTERIORS. Also see Red or Other Colors on Stone. See STAIN DIAGNOSIS on STONE for additional examples of diagnosing, cleaning, and preventing stains on building materials and artifacts.
Because lichens growing on a roof surface does not have as much thickness of body as moss, it will hold less water on the roof surface and is less of a wear factor than moss.
Our photographs (above) show lichens growing on an asphalt roof shingle in situ (above left). In the photo where our pen is inserted for scale (above right) we had "picked" the spot of lichens gently and flipped it over. Our pen points to the hole left in the asphalt shingle as the lichens had such a good grip on the mineral granules that when removing the lichens it brought some of the roof protective coating along with itself. If you click to enlarge the photo at above right you'll see the actual mineral granules from the shingle adhered in the "roots" of the lichens.
Moss Damage Compared with Lichens Damage to Roofs
Our photographs below show a Two Harbors Minnesota asphalt shingle roof with heavy moss and lichens growing on the same surface. You can see that comparing the loss of mineral granules where we have gently lifted off moss (below left) and where we used a knife blade to gently lift off lichens from the shingle surface (below right), both growths have loosened the mineral granule coating and exposed the organic shingle substrate in a similar fashion.
Notice that both roof photos show that both moss and lichens are happy to co-exist on the same shingle surface. Our photo at left shows testing where moss was lifted off of the shingle, and at right, cup lichens was pried off of the roof using the tip of a knife blade.
Because moss is a thicker growth on roof surfaces, we suspect that its ability to hold water and moisture on the roof surface is greater than that of lichens. So in some circumstances and climates, moss damage may be as severe or even more severe than lichens damage to a building roof, and we suspect that the degree of moss or lichens damage also varies by roofing material, with still more severe moss and water damage on wood shingle roofing.
If we have only lichens growing on a roof surface we would be less quick to try to clean it off since lichens not only has a tighter "grip" on the roof surface but the cleaning process for lichens risks doing more harm than good to the roof surface. Removing the protective granules from an asphalt shingle or mineral-granule coated roll roofing surface is going to reduce the future life of that roof covering.
Moss and lichens are more than a cosmetic issue on many kinds of roofing materials - asphalt shingles, roll roofing, wood shingle roofs, wood shake roofs. By holding moisture against the roof surface lichens but more so moss speed the wear of the asphalt shingle surface in freezing climates by increasing frost damage to the mineral granule coating on the shingles.
Frequently Asked Questions (FAQs) about lichens growth on roofs: damage, removal, prevention
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.