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Catalog of stains found on roof surfaces: Here is our catalog listing the 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.

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.

© Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

BLEED THROUGH - Black Bleed-Through or Extractive Bleeding Black Stains on Asphalt Shingles

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.

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.

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
B: Paler, otherwise no significant change
C: Darker
D: Darker and brownish
E: Black staining, "bleeding", and embedment of surface mineral matter
F: Dull black and formation of elephant skin.

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,

1. Shingle bleeding stains may be a clue that the asphalt mix for the particular shingle batch lacked adequate bonding, and
2. The loss of substrate material from a shingle may correlate with aging and wear. A change in shingle weight is the dominant feature appearing in shingle wear and the same article explains that loss of weight (caused by loss of surface material or loss of membrane material) correlates with shingle wear and life. Loss of volatile material correlates with loss of shingle flexibility which is a contributor to shingle wear and ultimately tears or cracking.

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.

Questions & Answers regarding this article

Questions & answers about how to diagnose, clean off, or prevent stains on roof surfaces, including extractive bleeding, algae, dirt and debris, moss, lichens.

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• InspectAPedia.com^® - Daniel Friedman - Publisher & Editor.
• InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also include a list of recommended books for the specific article topic as well as other references, and information sources.
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• Additional technical contributors & reference sources for this article are listed below.

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STAIN DIAGNOSIS on ROOFS
  Causes of Roof Stains
  Catalog of All Roof Stains
  ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES
  ALGAE STAIN TEST METHODS
  ALGAE STAINS ON ASPHALT ROOF SHINGLES
  Catalog of Black Roof Stains
  Black or Green Algae
  Black Stain Removal & Prevention
  Bleed-Through
  Chimney-Caused Roof Stains
  Debris Staining on Roofs
  EXTRACTIVE BLEEDING on SHINGLES
  Lichens on Roofs
  Moss on Roofs
  Power Washing Roofs
  Rust Stains on Shingles
  Soot Staining on Roofs

• Roger Hankey is principal of Hankey and Brown home inspectors, Eden Prairie, MN. Mr. Hankey is a past chairman of the ASHI Standards Committee. Mr. Hankey has served in other ASHI professional and leadership roles. Contact Roger Hankey at: 952 829-0044 - rhankey@hankeyandbrown.com. Mr. Hankey is a frequent contributor to InspectAPedia.com.
• 04/09: thanks to William M. Norman, P.E., S.E., Keeler-Webb Associates, 486 Gradle Drive, Carmel, IN 46032 for opening discussion regarding the legitimacy of extractive bleeding as a term to apply to asphalt roofing material. Mr. Norman suggests that many (not all) black stains on asphalt roofing may be due to algal growth. We will report progress in this discussion as updates to this web article.
• "A Performance Approach to Aging Tests for Bituminous Roofing Membranes", Einar M. Paulsen, Norwegian Building Research Institute, Trondheim, Norway, International Journal of Roofing Technology, 1990 Vol. 2., p. 27-39.
• Other online references to roofing standards, stains, bleeding questions include:
  • http://www.absoluteastronomy.com/topics/Asphalt
  • http://www.newworldencyclopedia.org/entry/Asphalt
  • http://www.esperanzaproperties.com/glossary.php?letter=b (see their entry for bleeding)
    http://www.sasolwax.com/More_about_Sasolwax_Flex.html (entry for roofing products)
  • Roofing Standards & Related Standards
    C772 Standard Test Method for Oil Migration or Plasticizer Bleed-Out of Preformed Tape Sealants
    D279 Standard Test Methods for Bleeding of Pigments
    D3018-90(1994)e1 Standard Specification for Class A Asphalt Shingles Surfaced with Mineral Granules
    D1079 Terminology Relating to Roofing, Waterproofing, and Bituminous Materials
    D228 Test Methods for Sampling, Testing, and Analysis of Asphalt Roll Roofing, Cap Sheets, and Shingles Used in Roofing and Waterproofing
    D3161 Test Method for Wind Resistance of Asphalt Shingles (Fan-Induced Method)
    E108 Test Methods for Fire Tests of Roof Covering
    and curiously, where reclaimed asphalt shingles were used as a road product, this topic came up as well at
    http://auto.ihs.com/collections/aashto/aashto-standards-2.htm

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

• Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
• Decks and Porches, the JLC Guide to, Best Practices for Outdoor Spaces, Steve Bliss (Editor), The Journal of Light Construction, Williston VT, 2010 ISBN 10: 1-928580-42-4, ISBN 13: 978-1-928580-42-3, available from Amazon.com
• The Journal of Light Construction has generously given reprint permission to InspectAPedia.com for this article. All rights and contents are ©Journal of Light Construction and may not be reproduced in any form.
• Architectural elements: the technological revolution: Galvanized iron roof plates and corrugated sheets; cast iron facades, columns, door and window caps, ... (American historical catalog collection), Diana S Waite, available used out of Amazon.
• Asphalt Roofing Residential Manual,
• Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724 ISBN-13: 978-0471331728
• Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008) ISBN-10: 1405161035 ISBN-13: 978-1405161039
• Built-Up Roof Systems, Manual, C.W. Griffin, Mcgraw-Hill (Tx); 2nd edition (July 1982), ISBN-10: 0070247838, ISBN-13: 978-0070247833
• Concrete Folded Plate Roofs, C. Wilby PhD BSc CEng FICE FIStructE (Author), Butterworth-Heinemann, 1998, ISBN-10: 0340662662, ISBN-13: 978-0340662663
• Concrete Shell Roofs, C. Wilby PhD BSc CEng FICE FIStructE (Author),
• Concrete Dome Roofs (Longman Concrete Design and Construction Series),
• Concrete Roofing Tile, History of the, Batsford, 1959, AISN B000HLLOUC (availble used)
• Copper Roofing, by CDA
• Copper Roofing, Master specifications for copper roofing and sheet metal work in building construction: Institutional, commercial, industrial, I.E. Anderson, 1961 (hard to find)
• Corrugated Iron, Building on the Frontier, Simon Holloway
• Green Roof Plants: A Resource and Planting Guide, Edmund C. Snodgrass, Lucie L. Snodgrass, Timber Press, Incorporated, 2006, ISBN-10: 0881927872, ISBN-13: 978-0881927870. The text covers moisture needs, heat tolerance, hardiness, bloom color, foliage characteristics, and height of 350 species and cultivars.
• Green Roof Construction and Maintenance, Kelley Luckett, McGraw-Hill Professional, 2009, ISBN-10: 007160880X, ISBN-13: 978-0071608800, quoting: Key questions to ask at each stage of the green building process Tested tips and techniques for successful structural design Construction methods for new and existing buildings Information on insulation, drainage, detailing, irrigation, and plant selection Details on optimal soil formulation Illustrations featuring various stages of construction Best practices for green roof maintenance A survey of environmental benefits, including evapo-transpiration, storm-water management, habitat restoration, and improvement of air quality Tips on the LEED design and certification process Considerations for assessing return on investment Color photographs of successfully installed green roofs Useful checklists, tables, and charts
• Handbook of Building Crafts in Conservation, Jack Bower, Ed., Van Nostrand Reinhold Company, NY 1981 ISBN 0-442-2135-3 Library of Congress Catalog Card Nr. 81-50643.
• Historic Preservation Technology: A Primer, Robert A. Young, Wiley (March 21, 2008) ISBN-10: 0471788368 ISBN-13: 978-0471788362
• Historic Slate Roofs : With How-to Info and Specifications, Tina Skinner (Ed), Schiffer Publishing, 2008, ISBN-10: 0764330012 , ISBN-13: 978-0764330018
• Low Slope Roofing, Manual of, 4th Ed., C.W. Griffin, Richard Fricklas, McGraw-Hill Professional; 4 edition, 2006, ISBN-10: 007145828X, ISBN-13: 978-0071458283
  • Roof failure causes in depth (and specific methods for avoiding them)
  • Roof design fundamentals and flourishes, based on voluminous industry research and experience
  • New technologies and materials -- using them safely and correctly
  • Comprehensive coverage of all major roofing systems pecifications, inspection, and maintenance tools for roofing work
• Metal Roofing, an Illustrated Guide, R.A. Knowlton , [metal shingle roofs],
• Patio Roofs, how to build, Sunset Books
• Problems in Roofing Design, B. Harrison McCampbell, Butterworth Heineman, 1991 ISBN 0-7506-9162-X (available used)
• Roofing The Right Way, Steven Bolt, McGraw-Hill Professional; 3rd Ed (1996), ISBN-10: 0070066507, ISBN-13: 978-0070066502
• Slate Roofs, National Slate Association, 1926, reprinted 1977 by Vermont Structural Slate Co., Inc., Fair Haven, VT 05743, 802-265-4933/34. (We recommend this book if you can find it. It has gone in and out of print on occasion.)
• Roof Tiling & Slating, a Practical Guide, Kevin Taylor, Crowood Press (2008), ISBN 978-1847970237,
  If you have never fixed a roof tile or slate before but have wondered how to go about repairing or replacing them, then this is the book for you. Many of the technical books about roof tiling and slating are rather vague and conveniently ignore some of the trickier problems and how they can be resolved. In Roof Tiling and Slating, the author rejects this cautious approach. Kevin Taylor uses both his extensive knowledge of the trade and his ability to explain the subject in easily understandable terms, to demonstrate how to carry out the work safely to a high standard, using tried and tested methods. 
  This clay roof tile guide considers the various types of tiles, slates, and roofing materials on the market as well as their uses, how to estimate the required quantities, and where to buy them. It also discusses how to check and assess a roof and how to identify and rectify problems; describes how to efficiently "set out" roofs from small, simple jobs to larger and more complicated projects, thus making the work quicker, simpler, and neater; examines the correct and the incorrect ways of installing background materials such as underlay, battens, and valley liners; explains how to install interlocking tiles, plain tiles, and artificial and natural slates; covers both modern and traditional methods and skills, including cutting materials by hand without the assistance of power tools; and provides invaluable guidance on repairs and maintenance issues, and highlights common mistakes and how they can be avoided. The author, Kevin Taylor, works for the National Federation of Roofing Contractors as a technical manager presenting technical advice and providing education and training for young roofers.
• The Slate Roof Bible, Joseph Jenkins, www.jenkinsslate.com, 143 Forest Lane, PO Box 607, Grove City, PA 16127 - 866-641-7141 (We recommend this book).
• Slate Roofing in Canada (Studi4es in archaeology, architecture, and history),
• Smart Guide: Roofing: Step-by-Step Projects, Creative Homeowner (Ed), 2004, ISBN-10: 1580111491, ISBN-13: 978-1580111492
• Solar heating, radiative cooling and thermal movement: Their effects on built-up roofing (United States. National Bureau of Standards. Technical note), William C Cullen, Superintendent of Documents, U.S. Govt. Print. Off (1963), ASIN: B0007FTV2Q
• Tile Roofs of Alfred: A Clay Tradition in Alfred NY
• "Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
• Wood Shingle Roofs, Care and Maintenance of wood shingle and shake roofs (EC), Stanley S. Niemiec (out of print)
• ...