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Black stains on building exterior stonework (C) InspectAPedia C&D Sandstone Stain Diagnosis, Cure, Prevention
How to Identify, Diagnose, Clean & Prevent Algae Stains on Sandstone Surfaces

  • STAINS on SANDSTONE, DIAGNOSE & CURE - CONTENTS: what are the causes & remedies for dark stains that appear on both natural and cultured sandstone? How should those stains be removed? How do experts control the development of algae or other stains from forming on standstone?
  • POST a QUESTION or READ FAQs 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.
  • REFERENCES
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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.



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Cause & Cure for Dark Stains on Sandstone, Re-Constituted Sandstone & Building Exterior Masonry Surfaces

Black stains on re-constituted sandstone on  a building exterior (C) InspectAPedia C&D

[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

Black stains on re-constituted sandstone on  a building exterior (C) InspectAPedia C&D Black stains on building exterior stonework (C) InspectAPedia C&D

Reply:

Black stains on building exterior stonework (C) InspectAPedia C&DWhile 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.

See ALGAE, FUNGUS, LICHENS, MOSS COMPARED for details.

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 SURFACE 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

Stone & Masonry Stains & Cleaning Articles

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Continue reading at STONE SURFACE CLEANING METHODS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see STAINS on CONCRETE

Or see LICHENS on STONE SURFACES

Or see STAIN DIAGNOSIS on BUILDING EXTERIORS - home

Or see STAINS on STONE, STUCCO DIAGNOSE & CURE

Suggested citation for this web page

STAINS on SANDSTONE, DIAGNOSE & CURE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING STAINS

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