Extractive Bleeding - Black Stains on Asphalt Roof Shingles
Does extractive bleeding really occur on roof shingles? Causes & Diagnosis of extractive bleeding stains.
EXTRACTIVE BLEEDING on SHINGLES - CONTENTS: Black or dark extractive bleeding stains on roof shingles - how do we sort out roof stains caused by algae, extractive bleeding, soot, debris or other causes?Diagnostic Guide to Extractive Bleeding Stains on Roof Surfaces. Definition of extractive bleeding roof shingles - does it really occur? Causes, cure, and prevention of extractive bleeding black stains on roof shingles
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Extractive bleeding stains found on asphalt shingle roof surfaces:
Definition of extractive bleeding; does extractive bleeding actually occur? what is extractive bleeding on roofs? Extractive bleeding can occur in some roofing products and is an asphalt shingle or roll roofing defect often confused with algae or other roof stains as well as an actual product failure. Is extractive bleeding different from black stains caused by roof algae?
Joining other roof stain sources, extractive bleeding stains on roof are part of a catalog of the types of black stains that are found on roofs. Black or dark stains on building roofs may be traced to extractive bleeding (or more often algae staining) where we find some asphalt shingle roofs offering a prime example.
BLEED THROUGH - Black Bleed-Through or Extractive Bleeding Black Stains May Occur on Asphalt Shingles or Roll Roofing
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.
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:
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.
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).
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
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,
Shingle bleeding stains may be a clue that the asphalt mix for the particular shingle batch lacked adequate bonding, and
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.
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.
Continue reading at ALGAE STAINS on ROOFS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
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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.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
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 - firstname.lastname@example.org. 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.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
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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
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).
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: email@example.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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