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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 |
Here is our catalog listing the types of black stains that are found on roofs, using asphalt shingle roofs as the prime example. This article series 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. See Causes of Roof Stains and Catalog of All Roof Stains for the causes and types of stains that occur on building roofs. There are other sources of roof staining, from cosmetic to harmful to the roof. For the diagnosis and cure of other building stains, see STAIN DIAGNOSIS on Building Exteriors and STAIN DIAGNOSIS on Indoor Surfaces. © Copyright 2009 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. BLEED THROUGH - Black Bleed-Through or Extractive Bleeding Black Stains on Asphalt ShinglesExtractive bleeding - bleed-through asphalt shingle stains may be mistaken for but are not black algae or black "fungus", nor are they soot. Extractive bleeding stains on asphalt shingles are caused by loss of black pigment in the asphalt mix intended to impregnate the shingle mat itself. Other black stains on roofs correlate with the growth of algae, the presence of roof debris or with soot from chimneys, particularly where an oil fired heating appliance is not operating properly. See Catalog of Black Roof Stains. Let's look further at extractive bleeding type stains:
Extractive bleeding or "bleed through" stains leaving black streaks running down an asphalt shingle roof is an indication of a defective roofing product. The chemistry of the shingle is permitting black pigment from the asphalt to leach to the shingle surface and run down the roof. Typically bleed-through on asphalt shingles appears as black streaks running down shingles. You'll see black streaks of varying length and width (photos above and at page top). Extractive bleeding on roof shingles originates at individual points: When the roof shingle staining or bleeding appears to run down the roof, originating from individual small points or "spots" (photos above) this is probably extractive bleeding or "asphalt roof shingle bleed through" on shingles - a product defect described by manufacturers as cosmetic. Extractive bleeding occurs on asphalt shingles when an excessive amount of bitumen is released from the shingle surface - we pose that this effect may occur because some of the bitumen was not well bound in the asphalt mix. Furthermore, bleed-through stains, since they are a feature of the asphalt shingle product itself, should occur on a roof regardless of the roof orientation, slope, or shading.By comparison, the location and pattern of black algae stains on an asphalt shingle roof are more likely to correlate with shade, areas of less sun exposure, or slope orientation (North) - factors that affect roof surface moisture, temperatures, and sun exposure - factors in algal growth. We describe and contrast black algae staining in the next section, just below. Because of variations during the shingle manufacturing process, and possibly because of variations in site conditions (sun, shading, slope, moisture), different roof areas or slopes on the same building may display different amounts of black staining. This term is commonly used with wood shingles where use of steel or possibly even copper nails can also produce staining. (Try stainless steel nails when re-roofing with wood shingles or shakes). Also see Roofing material defect / environmentally-caused roof shingle stains for more examples of this problem. Remedies for bleed through staining on asphalt shingles: we wouldn't do much to a roof with this staining since we worry that power washing or chemical treatments may reduce the remaining roof life. At re-roof time you might want to purchase a better-grade replacement shingle. Background on Asphalt Roofing Shingle or Roll Roofing Black Bleeding StainsExtractive bleeding is a term often applied to problems with paint or coatings over resin-containing wood products such as western red cedar shingles. But it has also been used in the roofing industry to describe bleed-out stains from asphalt roofing products. "Bleeding" in this context refers to the penetration of color from the underlying surface. Are all black roof stains algae? Some roofing experts such as Norman opine that the bleeding stains we discuss here are due to algae. Certainly in many cases black stains on asphalt roof products are due to algal growth, not extractive bleeding. See Black Algae for a description of black stains on roofs due to algae. Readers will notice that the pattern of stains we ascribe to algal growth (and include in roof photographs) do not appear as originating at a point. Where we find algae stains on roofs it appears in wider areas, it does not originate in an inverted vee point, and it is correlated with other roof conditions such as shaded spots or spots that tend to stay wet. There is less algae growth in areas of more sun. Also, on roofs where there is wash-down of salts from copper or aluminum flashing, you will see that it's effective in killing off algae (as well as moss and lichens). But on a roof with extractive bleeding you will see that the mineral salts washing down from similar flashings and metal at higher points does not make much of an impact on the black stain. Extractive bleeding of asphalt roof products was described in a peer reviewed professional journal, in an interesting article A Performance Approach to Aging Tests for Bituminous Roofing Membranes, under a discussion of roof weathering tests where the researchers defined changes in the surface appearance of roofing materials and named categories A-F: A: no significant change Bleeding of bituminous material was readily identified as a surface stain or discoloration on the roofing membrane. We pose that the loss of bitumen might signal a reduced roof shingle life for two reasons,
Some roofing consultants, including Mr. Norman (above) assert that many of the black stains on asphalt shingle roofs are due to algae growth and that extractive bleeding may not be a current roof problem. Free Testing Offered to Identify Roof Stain Material: see ALGAE STAIN TEST METHODS for a description of both free lab tests and do-it-yourself roof stain tests that can help decide on the cause, clean-up, and prevention of algae stains on roofs. See Black Algae for a description of black stains on roofs due to algae. If your roof stains are due to algae, see To remove and prevent black algae stains on roofs, see BLACK STAIN REMOVAL & PREVENTION. ... 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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04/28/2009 - 09/01/1995 - InspectAPedia.com/roof/Extractive_Bleeding_Shingles.htm - © Copyright 2008-1995 Daniel Friedman All Rights Reserved - InspectAPedia® is a Registered U.S. Trademark