FREE Encyclopedia of Building & Environmental Construction, Diagnosis, Maintenance & Repair The accuracy & trustworthiness of every article or Q&A is researched by human experts. See WHO ARE WE?
Sandstone Stain Diagnosis, Cure, Prevention How to Identify, Diagnose, Clean & Prevent Algae Stains on Sandstone Surfaces
POST a QUESTION or COMMENT On the cause, cure, & prevention of algae, fungus, moss or lichens stains & growth on exterior surfaces such as stone monuments, buildings, roofs, & other site features.
Algae, Moss, Lichens or other stains on sandstone surfaces of buildings or monuments:
This article discusses the causes & remedies for dark stains that appear on both natural and cultured sandstone? We address methods for removing stains from sandstone, and we discuss how experts control the development of algae or other stains from forming on standstone in the first place.
This article series describes and provide photographs and advice on identifying, cleaning, and preventing algae, moss, lichens, or fungal growth that occurs on stone surfaces such as buildings, gravestones, sidewalks, stone walls, and in nature. We include links to references useful in the identification of algae, moss, lichens, and mold. Our page top photograph algae growing on the stone wall at the entry to the dungeon of Goodrich Castle, Ross on Wye, Herefordshire, England U.K.
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?
Cause & Cure for Dark Stains on Sandstone, Re-Constituted Sandstone & Building Exterior Masonry Surfaces
[Click to enlarge any image]
Reader Question: Having looked on your website I was wondering if you could tell me if you think these black stains on this re constituted sandstone could be bacterial and what damage could this be doing and the best way to treat it. C&D 9/23/2014
...
Reply:
While bacteria may be a factor in black stains on masonry-like building exteriors, more often the colour is due to an algae or a fungus. That's what I see in your first three photos of black stains on building masonry exteriors.
At above right I see what looks like moss or algae or both on a brick wall inside corner where one would infer the presence of roof runoff spillage that might be better controlled or routed. But shade is also a factor in moss and algae growth on buildings.
And in our photo at left we see a heavy moss growth on the building balcony edge suggesting a long-standing combination of watr and possibly partial shade in this location.
Sandstone & Other Building Masonry Cleaning Advice for Black Stains, Moss, Algae
We discuss the cleaning/restoration of the stone grave marker shown at page top as well as other stone surface cleanign methods in more detail at STONE, STUCCO & BRICK CLEANING METHODS.
Watch out: Grimmer (1992) warns about using abrasives to clean stone exteriors, and further quoting another expert on cleaning sandstone:
Avoid the use of nonproprietary
acids on sandstone, which can
damage the material irreversibly.
Proprietary cleaning materials
fall into two categories—general
purpose and cleaners for metallic-sensitive masonry. Only cleaners for metallic-sensitive surfaces
should be considered.
Always use
a test panel and evaluate the re-
sults for at least two weeks be-
fore determining acceptability. - Schierhorn _ret. 2014)
In addition to reviewing the article above, you'll want to take a look at STONE CLEANING METHODS [live link is given below]
Also see the citations we offer below, particularly Grimmer (1992) and Christopher (1990)
Research on Re-Constituted Sandstone constituents, installation, troubleshooting, cleaning, repair
Alvarado, Giovanny, Neville Lui, and Matthew R. Coop. "Effect of fabric on the behaviour of reservoir sandstones." Canadian Geotechnical Journal 49, no. 9 (2012): 1036-1051.
ASTM C 119-94a, “Standard Terminology
Relating to Dimension Stone,” ASTM, American Society for Testing and Materials,
100 Barr
Harbor Dr., West Conshahocken, PA 19428
Boornazian, Glenn, and Norman R. Weiss. "SANDSTONE: HISTORY OF USE AND PRESERVATION." Structural repair and maintenance of historical buildings (1989): 469.
Clifton, James R. "Laboratory evaluation of stone consolidants." Studies in Conservation 29, no. Supplement-1 (1984): 151-155.
Christopher, D. "Exterior Cleaning of Sandstone Buildings in Edinburgh: Technical and Aesthetic Considerations: Submitted for the Degree of Master of Science [Architectural Conservation]." PhD diss., School of Architecture, Edinburgh College of Art/Heriot-Watt University, Edinburgh, 1990.
Dajnowski, A. "Laser cleaning of the Nickerson Mansion: The first building in the US entirely cleaned using laser ablation." In Lasers in the Conservation of Artworks: Proceedings of the International Conference Lacona VII, Madrid, Spain, 17-21 September 2007, vol. 3, p. 209. CRC Press, 2008.
Dapples, E. C. "Some concepts of cementation and lithification of sandstones." AAPG Bulletin 56, no. 1 (1972): 3-25.
Dimension
Stone
Design
Manual
IV
,
1991, Marble Institute of America, 33505
State St., Farmington, MI 48335
Grimmer, Anne E. KEEPING IT CLEAN: REMOVING EXTERIOR DIRT, PAINT, STAINS AND GRAFFITI FROM HISTORIC MASONRY BUILDINGS [PDF] Washington, D.C.: Preservation Assistance Division, National Park Service, U.S. Department of the Interior, 1988. - retrieved 2022/10/08, original source: https://www.nps.gov/tps/how-to-preserve/preservedocs/Keeping-It-Clean.pdf
Excerpt: The purpose of this technical report is to
provide information on removing dirt,
stains, paint and related coatings, graffiti,
and other disfiguring or potentially harmful
substances from exterior masonry.
Grimmer, Anne E. DANGERS OF ABRASIVE CLEANING TO HISTORIC BUILDINGS [PDF] (1979) [Department of the Interior], Heritage Conservation and Recreation Service [Office of Archeology and Historic Preservation], Technical Preservation Services Division, 1979.
Heidelmann, Hendrik. "Voruntersuchungen zum Zustand der Architekturteile und des plastischen Zierats des Sandsteinbaus der Kunstakademie Dresden." Arbeitsblätter für Restauratoren. Gruppe 6. Stein 27, no. 2, Gruppe 6 (1994): 313-318.
Herget, Frederick A., and Robert W. Crooks. "Deterioration and Stabilization of Berea Sandstone on the Hamilton County Courthouse." ASTM SPECIAL TECHNICAL PUBLICATION 1180 (1993): 412-412.
Hyslop, Ewan. The performance of replacement sandstone in the new town of Edinburgh: evidence from grant-aid repair schemes of the Edinburgh new town conservation committee. Historic Scotland, 2004.
Leitch, E. C., V. J. Morand, C. L. Fergusson, R. A. Henderson, and P. F. Carr. "Accretion and post‐accretion metamorphism in subduction complex terranes of the New England fold belt, eastern Australia." Journal of Metamorphic Geology 11, no. 3 (1993): 309-318.
Preston, John. "The surface restoration of buildings–An investment in the present as well as in the future." Structural Survey 7, no. 4 (1989): 450-460.
Sargent, Karen. "Exterior sandstone restoration of Alexander Hall." In Preservation and restoration of cultural heritage: proceedings of the 1995 LCP Congress, Montreux, 24-29 September 1995= Conservation et restauration des biens culturels: actes du congresLCP 1995, Montreux, 24-29 septembre 1995, pp. 231-234. Laboratoire de conservation de la pierre, 1996.
Schierhorn, Carolyn. "Sandstone." [PDF] retrived 9/23/2014, original source: http://www.masonryconstruction.com/Images/ Sandstone_%20Earth%27s%20Vivid%20Palette_tcm68-1375439.pdf
Torraca, Giorgio. Porous Building Materials . Rome: ICCROM, 1988.
Torraca, Giorgio. Solubility and Solvents for Conservation Problems. Rome: ICCROM, 1990.
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Reader Comments, Questions & Answers About The Article Above
Below you will find questions and answers previously posted on this page at its page bottom reader comment box.
(Oct 9, 2011) جوري اوسي said: this is beautiful a pohto
Question:
(May 5, 2012) Evelyn Neber said: Question: Thick black patches that looked like moss, covered the concrete walls and exteriors of the basement access, outside my ground floor apartment. Last spring, after a HUD inspection of our complex, the basement was cleaned up:they even had some outside workers in white covered suits come and they power -sprayed and cleaned the whole cellar and the outside. The black moldy mossy patches(some were a couple inches in diameter) are gone. But my almost new through-wall air conditioner which was right up the cellar stairwell has had surges of but black goopy things flying through it onto my carpet and dining/living room. I also always have black mold spots all over the blades inside the a/c which I try to clean with q-tips but they always come back. I've never experienced anything like this in my life
. Was this black mold ? The superintendent will not tell me. Do I have any rights? Are they responsible to clean my air conditioner? I live in HUD housing. I am disabled, have what is called probable sarchoidosis and suffer from have asthma and allergy attacks. Can you direct me to where I could possibly go to find out if I have any rights in this situation. Thank you.
Reply:
(June 5, 2012) Angela T. said:
@Evelyn Neber:
It's difficult to determine whether or not your particular situation is harmful black mold or algae. Given the black patches were on the building's exterior, my opinion is that it's algae stains and fungal growth. Black mold is typically found on the building's interior (walls, basement structural joists) where moisture and humidity levels are consistently high.
The white coveralls you saw were most likely used to protect the workers from the cleaning chemicals, usually good ol' bleach, from damaging their clothers or irratating their skin.
Your through-wall air conditioner may have been subjected to the high-pressure water washing and algae run-off, hence the surges and intake of algae.
I'm surprised the superintendent or contractors didn't advise you to turn off the a/c and cover it while they performed their work, so that the mechanisms and filters would be protected. With this said, tenants in HUD housing have certain rights that vary from state to state.
For instance, California has the Toxic Mold Protection Act passed in 2001 that requires landlords to disclose mold discoveries to existing or prospective tenants and the remediation methods taken. Your best action would be to contact your local HUD agency to find out your rights relevant to the state you live in.
Moderator said:
Thanks Angela T., your comments are spot-on.
Question: how do I get rid of algae on my river rocks and rose beds?
(July 13, 2012) Theresa Cremona terric1011@gma said: I have algae coming from my air conditioner in the corner of my concrete home in Florida. It is green and staining my river rocks in the beds. I have rose plants there. How do I get rid of the algae.
Reply:
Theresa the article above describes how to clean off algae, but to stop the problem you will need to find and fix the water source - in this case rerouting the condensate drain to a location that doesn't bother your plantings.
Question: white lichens on living roof fireplace stone wall
(Mar 4, 2014) Kristine Creery said: We recently purchased a home that has a living room fireplace surrounded by a natural stone wall. A white lichen is growing in some spots, ranging from dime size to fifty cent piece size.
We have cleaned the stone and are trying to remove the spots (by scraping with a putty knife - very gently so as not to damage stone). What is the best way to remove the spots and how do we keep them from growing back? We want to enhance and seal the stone soon. Thanks so much!
Reply:
Hi Kristine.
I would like to see some sharp photos including closeups. It would be odd to find lichens growing indoors in a home at normal humidity range. Perhaps it's something else like efflorescence?
Question: pink stones on siding when it rains
(July 2, 2015) Ian said: The outside North facing wall of our house show pink staining when it rains but disappears when dry I am told that this is a fungus. The walls are white Arctic finish How do I treat this Thanks
Reply:
Ian:
You're asking this question on a stone stain diagnosis page. Are your house walls stone or some other material? The solution may depend in part on how the walls are built.
There are fungi and also algae blooms that can stain walls pink, but I'm surprised that the stains are only visible when wet. PResuming the walls are painted you might try adding a fungicide to your next paint job.
Question: white crust on our stone house
(Nov 30, 2015) Anonymous said: Seeba Perincheril We see a white crust like stuff on our exterior stone work of our house. I think the stone is fake. Our house is South facing and gets lots of sun to that area. What do you think it is and how can we clean that? Thanks
Reply:
Seeba, please search InspectApedia for EFFLORESCENCE to read about what I think you may be seeing.
Use the page top or bottom CONTACT link to send me some photos for further comment.
Question: bright green mold on flagstones
(Mar 20, 2016) Jan Sutherberry said: My flagstones have only been down for two and a half years in my back garden. Only in the middle area of the garden has bright green mould. Could you tell me what it could be?
Reply:
Jan
Outoors mold and algae will grow freely, as will moss, on hospitable surfaces, moreso in damp, wet, or shaded areas.
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In addition to any citations in the article above, a full list is available on request.
[1] Graphic Guide Ontario Mosses (some of which appear widely dispersed by climate and geographic area, not just in Ontario) which offers a graphic guide to mosses. worldofmosses.com/ggom/index.html
[2] Also see the sources listed at worldofmosses.com/ggom/ggomBibliography.html
[3] Also see the Journal Folia Geobotanica, Springer, Netherlands ISSN1211-9520 (Print) 1874-9348 (Online) IssueVolume 11, Number 2 / June, 1976 DOI10.1007/BF02854759 Pages217-22
[4] The Ecology of Algae, F.E. Round, Cambridge University Press, 1984 ISBN-10: 0521269067 ISBN-13: 978-0521269063 After an introduction outlining the chemical and physical characteristics of the environment, the book goes on to look at the actual habitats in which algae occur. The communities of the individual habitats such as open water, sediments, rocky shores, coral reefs, hot springs, sea ice, soil, etc., are then discussed with special phenomena highlighted, for example rhythmic activity, nitrogen fixation and buoyancy. There are also chapters on seasonal cycles of algal growth, energy flow, geographical dispersion, palaeo-ecology and contribution to sediments. The importance of algae in symbiotic relationships and their considerable significance to animal grazers in aquatic food chains are also discussed. The final chapter deals with the relationships of algae to eutrophication and pollution of water. This is an important aspect, which can only be understood through an appreciation of algal ecology.
[5] Lichens of North America, Irwin M. Brodo, Yale University Press, 2001, ISBN-10: 0300082495, # ISBN-13: 978-0300082494 Quoting from Library Journal: Lichens are a combination of a fungus and an alga but have a unique structure and appearance quite different from either. Existing worldwide and growing on a variety of surfaces, including rocks, soil, and trees, they may appear leafy, shrubby, mossy, crusty, or jellylike and are seen in a wide range of colors, from brilliant oranges, yellows, and reds to dull grays and browns. This huge new book, written by a world authority on lichens and emeritus research scientist at the Canadian Museum of Nature, Ottawa, provides information on about 1500 of the roughly 3600 recognized North American lichens. Part 1 introduces lichens in 14 clearly written chapters that discuss their biology, ecology, geography, environmental roles, and collection. Part 2, the heart of the book, is a guide that offers identification keys to groups, genera, and species and their descriptions, with accompanying photographs and North American distribution maps. The more than 900 truly beautiful, full-color photos were taken by the Sharnoffs, nature photographers whose work has been widely published in National Geographic, Smithsonian, and elsewhere. Of value to professionals and amateurs alike, this book is certain to be a classic reference for decades to come. Highly recommended for academic and research libraries and for public libraries where interest warrants; libraries needing only a brief yet informative introduction to lichens should consider William Purvis's inexpensive Lichens (Smithsonian Institution, 2000). William H. Wiese, Iowa State Univ. Lib., Ames
[6] Cultural Heritage and Aerobiology, Methods and Measurement Techniques for Biodeterioration Monitoring, Paolo Mandrioli, Guilia Caneva, and Cristina Sabbioni, Eds., Kluwer Academic Publishers, 2003 ISBN 1-4020-1622-0 See our book review of this reference. The conservation of art objects relies on expert inspection, testing, and diagnosis of environmental contaminants and factors that affect the deterioration of artworks, such as mold, moisture, temperature, acid rain, and both indoor and outdoor air quality components. This text reviews these important art conservation concerns and describes methods for the inspection, testing, and monitoring of environmental conditions wherever artworks and other cultural artifacts are located.
[7] "Assessing Cleaning and Water-Repellent Treatments for Historic Masonry buildings", Robert C. Mack, FAIA, Anne Grimmer U.S. National Park Service, web search 07/24/2010, original source: http://www.nps.gov/hps/tps/briefs/brief01.htm Quoting from the document introduction: The purpose of this Brief is to provide information on the variety of cleaning methods and materials that are available for use on the exterior of historic masonry buildings, and to provide guidance in selecting the most appropriate method or combination of methods. The difference between water-repellent coatings and waterproof coatings is explained, and the purpose of each, the suitability of their application to historic masonry buildings, and the possible consequences of their inappropriate use are discussed. The Brief is intended to help develop sensitivity to the qualities of historic masonry that makes it so special, and to assist historic building owners and property managers in working cooperatively with architects, architectural conservators, and contractors. Although specifically intended for historic buildings, the information is applicable to all masonry buildings. This publication updates and expands Preservation Briefs 1: The Cleaning and Waterproof Coating of Masonry buildings. The Brief is not meant to be a cleaning manual or a guide for preparing specifications. Rather, it provides general information to raise awareness of the many factors involved in selecting cleaning and water-repellent treatments for historic masonry buildings.
[8] Thanks to Patrick Walsh for discussing cleaning methods for gravestones & tombs May 2010
[9] Shingle Shield™ are zinc strips that are inserted under the shingle tabs of individual shingles to reduce moss, lichens, and algae growth on asphalt roofing - see shingleshield.com
[10] StainhandleR are zinc strips that are inserted under the shingle tabs of individual shingles to reduce moss, lichens, and algae growth on asphalt roofing- see stainhandler.com
[11] Zinc-Shield® - zincshield.com and Z-stop™ zinc roofing strips - z-stop.com, are roll-out zinc strips intended for installation near the ridge of a roof to reduce moss, lichens, and algae growth on roofs
[12] 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.
[13] How to Recognize & Control Sooty Molds, USDA publication on the recognition and control of black sooty molds, including on buildings.
This publication is also available in printed form from the U.S. Government Printing Office, 1992 657-152 HT-69 1992. The original article was authored by Kenneth K. Kessler, Jr., Principal Plant Pathologist, U.S. Forest Service, in the Department of Agriculture of the United States. Copies are also available from North Central Distribution Center, Forest Products Laboratory, One Gifford Pinchot Dr., Madison WI 53705-2398.
[14] "Microbes Eating Away at Pieces of History", Vina Venkataraman, The New York Times, 27 June 2008 p. F3.
[15] Allsopp D.,
Seal K. J.
(1986) Biodeterioration of refined and processed materials. Introduction to biodeterioration. (Edward Arnold, London, United Kingdom), pp 51–53.
[16] Bock E.,
Sand W.,
Meincke M.,
Wolters B.,
Ahlers B.,
Meyer C.,
Sameluck F.
(1988) Biologically induced corrosion of natural stones—strong contamination of monuments with nitrifying organisms. in Biodeterioration, eds Houghton D. R., Smith R. N., Eggins H. O. W. (Elsevier Applied Science, New York, N.Y.), 7:436–440.
[17] Bock E.,
Sand W.
(1993) The microbiology of masonry biodeterioration. J. Appl. Bacteriol. 74:503–514.
[18] Griffin P. S.,
Indictor N.,
Koestler R. J.
(1991) The biodeterioration of stone: a review of deterioration mechanisms, conservation case histories, and treatment. Int. Biodeterior. 28:187–207.
[19] Grilli Caiola M.,
Forni C.,
Albertano P.
(1987) Characterization of the algal flora growing on ancient Roman frescoes. Phycologia 26:387–390.
[20] Ortega-Calvo J. J.,
Hernandez-Marine M.,
Saiz-Jimenez C.
(1993) Cyanobacteria and algae on historic buildings and monuments. in Recent advances in biodeterioration and biodegradation, eds Garg K. L., Garg N., Mukerji K. G. (Naya Prokash, Calcutta, India), I:173–203.
Paint Handbook: testing, selection, application, troubleshooting, surface preparation, etc., Guy E. Weismantel, Ed., McGraw Hill Book Company, 1981, ISBN-10: 0070690618, ISBN-13: 978-0070690615, [Excellent but a bit obsolete paint theory and practice, also a bit light on field investigation methods, out of print, available used-DF] How to select and apply the right paint or coating for any surface. The first major reference to help you choose the correct paint or other finish to do the job best on a particular surface exposed to a particular environment. Experts in the field give full advice on testing surface preparation, application, corrosion prevention, and troubleshooting. The handbook covers wood, metal, composites, and masonry, as well as marine applications and roof coatings. A ``must'' working tool for contractors, architects, engineers, specification writers, and paint dealers.
Paint and Surface Coatings, Theory and Practice, R. Lambourne & T.A. Strivens, Ed., Woodhead Publishing Ltd., William Andrew Publishing, 1999 ISBN 1-85573-348 X & 1-884207-73-1 [This is perhaps the leading reference on modern paints and coatings, but is a difficult text to obtain, and is a bit short on field investigation methods - DF] Provides a comprehensive reference source for all those in the paint industry, paint manufacturers and raw materials suppliers, undergraduate and postgraduate students, and industrial paint users. R. Lambourne was in the Research Department at ICI Paints Division and the Industrial Colloid Advisory Group, Birstol University, UK.
Art, Biology, and Conservation: Biodeterioration in Works of Art, Robert J. Koestler et als. Eds., Metropolitan Museum of Art, 2003, ISBN 1-58839-107-8
In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: info@carsondunlop.com. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Carson Dunlop Associates provides extensive home inspection education and report writing material. In gratitude we provide links to tsome Carson Dunlop Associates products and services.