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InspectAPedia ® Home ROOFING INSPECTION & REPAIR AGE OF ROOFING ALUMINUM ROOFING AMERICAN CEMWOOD ROOFING ARCHITECTURE & BUILDING COMPONENT ID ASBESTOS IDENTIFICATION IN buildings ASBESTOS CEMENT ROOFING ASBESTOS MATERIAL REGULATIONS ASPHALT ROOF SHINGLES ATTIC CONDENSATION CAUSE & CURE BEST CONSTRUCTION PRACTICES GUIDE BEST ROOFING PRACTICES BUILDING SAFETY HAZARDS GUIDE BUILT UP ROOFS CEMWOOD ROOFING CERTIFICATIONS for ROOFING CONTRACTORS CHIMNEY INSPECTION & REPAIRS CHIMNEY FLASHING Mistakes & Leaks CHOOSING A ROOFING CONTRACTOR CLAY TILE ROOFING CLAY, CONCRETE, FIBER CEMENT TILE INSTALLATION COOLING LOAD REDUCTION by ROOF VENTS CORRUGATED ROOFING COPPER ROOFING DEBRIS STAINING on ROOFS DECKS, ROOFTOP CONSTRUCTION DEFINITIONS of ENGINEERED WOOD OSB LVL etc DISASTERS: BUILDING INSPECTION & REPAIR DISPUTE RESOLUTION on ROOF JOB PROBLEMS ENERGY SAVINGS in buildings EPDM, RUBBER, PVC ROOFING EPDM ROOF LEAK REPAIRS EXTRACTIVE BLEEDING on SHINGLES FELT UNDERLAYMENT REQUIREMENTS FIBER CEMENT & FIBERBOARD ROOFING FIRE RATINGS for ROOF SURFACES FIRE RETARDANT PLYWOOD FLASHING on BUILDINGS FLASHING, ASPHALT SHINGLE VALLEYS FLASHING, CHIMNEY Mistakes & Leaks FLASHING, CLAY TILE ROOFS FLASHING MEMBRANES PEEL & STICK FLASHING for METAL ROOFS FLASHING ROOF WALL DETAILS FLASHING ROOF-WALL SNAFU FLASHING SIDING DETAILS FLASHING WALL DETAILS FLASHING WINDOW DETAILS FLASHING WOOD ROOF DETAILS FLAT ROOF MOISTURE & CONDENSATION GALVANIC SCALE & METAL CORROSION Green House or Solarium Roof Leaks GUTTERS & DOWNSPOUTS HAIL DAMAGED SHINGLES HEAT TAPES & CABLES on Roofs for Ice Dams HOT ROOF DESIGNS: Un-Vented Roof Solutions HOUSEWRAP INSTALLATION DETAILS HUMIDITY LEVEL TARGET ICE DAM PREVENTION INSECT INFESTATION / DAMAGE INSULATION IDENTIFICATION GUIDE INSULATION INSPECTION & IMPROVEMENT LEAD POISONING HAZARDS GUIDE LEAKY ROOF DIAGNOSIS & REPAIR LEED GREEN BUILDING CERTIFICATION LOW SLOPE ROOFING MEMBRANE ROOFING METAL ROOFING MODIFIED BITUMEN ROOFING NOISE / SOUND DIAGNOSIS & CURE NOISE CONTROL for ROOFS PLASTIC ROOFING TYPES PVC, EPDM, RUBBER ROOFING ROLL ROOFING, ASPHALT ROOF ARCHITECTURAL STYLES - PHOTO GUIDE ROOF CLEANING RECOMMENDATIONS ROOF COLOR RECOMMENDATIONS ROOF DORMER TYPES - PHOTO GUIDE ROOF INSPECTION SAFETY & LIMITS ROOF SLOPE DEFINITIONS ROOF NOISE TRANSMISSION ROOF REPLACEMENT SNAFUs ROOF SLOPE DEFINITIONS ROOF VENTILATION SPECIFICATIONS ROOF VENTING ENERGY SAVING DETAILS ROOFING FELT UNDERLAYMENT REQUIREMENTS ROOFING MATERIALS, Age, Types ROOFING TILE SHAPES & PROFILES ROOFING UNDERLAYMENT BEST PRACTICES RUBBER, EPDM, PVC ROOFING SADDLE CONSTRUCTION at CHIMNEYS SLATE ROOF INSPECTION & REPAIR SNOW GUARDS & SNOW BRAKES SOD ROOFING SOUND CONTROL in buildings STAIN & BIODETERIORATION AGENT CATALOG STAINS on & in BUILDINGS, CAUSES & CURES STAIN DIAGNOSIS on BUILDING EXTERIORS STAIN DIAGNOSIS on BUILDING INTERIORS STAINS on INDOOR SURFACES: PHOTO GUIDE STAINS & Thermal Tracking STAIN DIAGNOSIS on ROOFS STAIN DIAGNOSIS on STONE STONE CLEANING METHODS STRESS SKIN INSULATED PANELS TEST LABS - ROOF SHINGLE THATCH ROOFING WALK-ON ROOF SURFACES WARRANTIES for ROOF SHINGLES WIND DAMAGE to ROOFS WOOD SHAKE & SHINGLE ROOFING WORKMANSHIP & ROOF DAMAGE ZINC METAL ROOFING More Information |
Extractive bleeding stains found on asphalt shingle roof surfaces: does extractive bleeding actually occur? what is it - an asphalt shingle defect often confused with algae or other roof stains as well as an actual product failure forming part of our catalog of he types of black stains that are found on roofs, using extractive bleeding (or more often algae staining) on asphalt shingle roofs as a 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. Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman. 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.
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). 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: 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 BUILDING INTERIORS. 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 or Green 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 or Green 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. Frequently Asked Questions (FAQs)... Ask a Question or Search InspectApediaQuestions & answers or comments about how to diagnose, clean off, or prevent stains on roof surfaces, including extractive bleeding, algae, dirt and debris, moss, lichens. Ask a Question or Enter Search Terms in the InspectApedia search box just below. Technical Reviewers & ReferencesRelated Topics, found near the top of this page suggest articles closely related to this one.
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