Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
ROOFING INSPECTION & REPAIR
AGE OF 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
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
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
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 VENTILATION 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
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
WALK-ON ROOF SURFACES
WARRANTIES for ROOF SHINGLES
WIND DAMAGE to ROOFS
WOOD SHAKE & SHINGLE ROOFING
WORKMANSHIP & ROOF DAMAGE
ZINC METAL ROOFING
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.
Extractive 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 Stains
Extractive 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.
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
No FAQs have been posted for this page. Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Questions & 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 & References
Related Topics, found near the top of this page suggest articles closely related to this one.