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ROOFING INSPECTION & REPAIR ASBESTOS CEMENT ROOFING ASPHALT ROOF SHINGLES ASPHALT SHINGLE DEFINITIONS ASPHALT SHINGLE FAILURE TYPES ALGAE, FUNGUS, LICHENS, MOSS COMPARED ALGAE STAINS ON ASPHALT ROOF SHINGLES ALGAE STAIN TEST METHODS ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES BLACK STAIN REMOVAL & PREVENTION BLISTERS on ASPHALT SHINGLES CRACKS in FIBERGLASS SHINGLES CUPPING ASPHALT SHINGLES CURLING ASPHALT SHINGLES FISHMOUTHING ASPHALT SHINGLES GRANULE LOSS from SHINGLES HAIL DAMAGED SHINGLES LADDERING & STAIR STEPPING SHINGLES LIFE / WEAR FACTORS in SHINGLES MECHANICAL DAMAGE of SHINGLES MOSS & LICHENS on SHINGLES ORGANIC FELT SHINGLE DEFECTS SPLICE DEFECTS on ASPHALT SHINGLES STAINS on ROOF SHINGLES WHAT ARE ASPHALT SHINGLES BUILT UP ROOFS CERTIFICATIONS for ROOFING CONTRACTORS CHIMNEY INSPECTION & REPAIRS CHOOSING A ROOFING CONTRACTOR CLAY TILE ROOFING FIRE RETARDANT PLYWOOD LOW SLOPE ROOFING MATERIALS MEMBRANE ROOFS METAL ROOFING TYPES MODIFIED BITUMEN ROOFING ROOF INSPECTION SAFETY & LIMITS ROOF VENTILATION SPECIFICATIONS ROOF VENTING ENERGY SAVING DETAILS SLATE ROOF INSPECTION & REPAIR SLATE ROOF DURABILITY SLATE ROOF REPAIRS SLATE ROOF SOURCES SLATE ROOF TYPES SLATE ROOF PHOTO LIBRARY SLATE ROOF INSPECTIONS SLATE ROOF INSPECTION CLASS SOD ROOFING SIDING WOOD STAIN DIAGNOSIS on Building Exteriors STAIN DIAGNOSIS on Roofs Causes of Roof Stains Catalog of All Roof Stains Catalog of Black Roof Stains Black Algae ALGAE STAIN TEST METHODS Black Stain Removal & Prevention Bleed-Through Chimney-Caused Roof Stains Debris Staining on Roofs Lichens on Roofs Moss on Roofs Rust Stains on Shingles Soot Staining on Roofs STAIN DIAGNOSIS on Indoor Surfaces STAINS on Indoor Surfaces: PHOTO GUIDE STANDARDS for ROOFING STONE ROOFING THATCH ROOFING WARRANTIES for ROOF SHINGLES WOOD SHAKE & SHINGLE ROOFING WORKMANSHIP & WIND DAMAGE More Information InspectAPedia Blog - News Updates Air Conditioning & Heat Pumps Bookstore Electrical Environment Exteriors Heating Home Inspection Insulate Ventilate Interiors Mold Inspect/Test Plumbing Water Septic Roofing Structure Accuracy & Privacy Policies Contact Us |
This document tells readers how to identify & explain the most-common causes of black, brown, red, gray, green, or white stains appearing on roof shingles and on other building surfaces. Roof shingle stains are often caused by black algae, bleed-through or extractive bleeding of asphalt, dirt, soot, or organic debris. But there are other sources of roof staining and they vary in significance, from cosmetic to harmful to the roof. Here we give an index of all sorts of roof stains and what causes them. For the diagnosis and cure of other building stains, see STAIN DIAGNOSIS on Building Exteriors and STAIN DIAGNOSIS on Indoor Surfaces. The remedies for and means of preventing stains on roof shingles are discussed as well. In the photo shown here, the black stains on the lower roofs are bleed-through or extractive bleeding. The upper roof, shaded by the large tree in the photo, was also moss covered. Notice the streak of "clean" roof shingles that lack the stains on the upper roof near its left edge? Those shingles were installed down-roof from an aluminum attic vent fan cover. The aluminum salts washing off of the fan cover prevented moss, lichens, and algae from growing on those shingles. Also see ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES where we discuss not only moss and lichens but black fungal stains on asphalt shingles and other roof types. © Copyright 2010 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website. How to Distinguish Roof Stain by Type of CauseAs for distinguishing between an algae growing on shingles and a fungus growing on roof shingles, building or environmentally-caused roof staining, or other causes, here are several approaches: Visual Roof Inspection & Roof Stain Area Context Help Diagnose Cause of Roof StainsProximate cause roof shingle stains
If you see a roof stain that develops only in limited areas of a single roof slope look for a relation between the stained area and a proximate cause such as a sooty chimney top or a tree that shades that section of the roof or drops organic debris onto it. These include tree shade caused moss, tree-shade caused lichens growth on a roof, or dark stains on roof coverings caused by organic debris such as leaves and sticks that fall onto and collect on the roof surface (photo at left). Our photo at above right shows brown stains below a metal roof chimney. Probably more important, this chimney has lost its cap, risking damage to and unsafe conditions at the building heating equipment. See Debris Staining (trees), see ALGAE STAINS ON ASPHALT ROOF SHINGLES (algae) and Soot Staining(chimneys). Roofing material defect / environmentally-caused roof shingle stains.
Our stained asphalt roof shingle photo at above lefty show black extractive bleeding stains on roof shingles colored other than white. Even on darker shingles these effects may occur. See Black Bleed-Through or Extractive Bleeding Black Stains on Asphalt Shingles. Click to enlarge our stained shingles photo at above left and you may also notice vertical cracks running up through shingles to the left of the dormer. This roof may also have a defective roof product causing splitting shingles (see CRACKS in FIBERGLASS SHINGLES). We're not certain about the cause of the staining at above right. It is probably extractive bleeding but a second candidate might be roof algae. We need a closer look. If the stain pattern on a roof surface occurs across the entire field of the roof and independent of proximate causes like chimneys or trees, it is more likely due either to the roofing material itself (possibly extractive bleeding), the overall environment (downwind from a chemical plant or incinerator or factory), or due to the slope' orientation (North slope, cooler, East or West roof slope -more sunlight). See SHINGLE LIFE / WEAR FACTORS for a discussion of sunlight effect on roof life. While we have not confirmed its presence, some black stains on roofs and roof gutters might be due to black molds or sooty molds, for which the USDA has published How to Recognize & Control Sooty Molds. Black mold growth on leaves, on roof debris that has fallen from a tree overhead, or on an aluminum roof gutter, is not a predictor that any of the species discussed in the USDA article will appear as black "sooty mold" growth on a roof shingle. The chemistry of roof shingles, their granule coverings, and substrates is quite different from other organic substances
that are home to many molds. Further, many newer shingle products include chemicals to retard black algae growth that
may also retard mold growth. Specific mold genera/species like to grow on particular surfaces - it's their food, and while The roof cleaning methods to remove black algae will probably work well for black mold growth on a roof as well. Roofing material defect / installation / structurally-caused roof shingle stainsIf you see roof staining or defects that occur on all roof slopes regardless of slope orientation or presence/absence of proximate causes (chimneys, trees) then the condition may be due to roofing material, its installation, or the building itself (inadequate under roof venting). Forensic sampling of Roof Stain MaterialA simple collection of the stained material using clear adhesive tape followed by a laboratory analysis by an experienced microscopist is conclusive. We don't recommend lab sampling of shingle stains in most cases but if you want to sample a stain material for analysis in our forensic laboratory, instructions are at Six Easy Steps to Get and Mail a Mold Test Kit. Don't bother worrying about mildew on your roof. Mildew is an obligate parasite which grows only on living plants. Unless your roof is covered with grapes it is not likely to have much mildew there. Online Guide to Types of Stains on Building Roofs, Surfaces, WallsIn the following guide we list types of stains by stain color & appearance, by building location or material, and by stain cause. We distinguish among the following stuff that may stain or be found growing building roofs, walls, or other surfaces, with extra focus on asphalt shingle roofs as well as other roofing materials such as wood shingles, wood shakes, roll roofing, and even slate or tile roofs. Some of these types of roof stains or discoloration are only cosmetic in nature, while others may indicate growths that are likely to reduce the roof covering life. A more detailed, illustrated version of the list below is given at Stain Diagnosis on Building Exteriors.
... Technical Reviewers & References
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website. ASPHALT ROOF SHINGLES
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