Photo-guide to Identification of Algae, Fungus, Lichens, Moss on or in buildings
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Photographs of Algae, lichens, moss, mold help identify these substances in nature and on buildings
Microphotographs of algae, lichens, moss, mold: high magnification views of algae, lichens, moss, mold to 1200x detail characteristics of these organisms
What is the difference between moss and algae or moss and lichens? Do they affect buildings differently?
We provide photos and text to help distinguish among algae, lichens, moss and mold growths on any surface.
Questions & answers about algae, lichens, and moss growth on buildings: cause, remedy, prevention

This article describes and provide photographs and microscopic photographs of algae, moss, lichens, or fungal growth that occurs on buildings and in nature. We include links to references useful in the identification of algae, moss, lichens, and mold. Our photo at page top shows moss on an asphalt shingle roof.

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What does Algae look like on buildings and under the microscope?

This article series tells readers how to identify, evaluate, remove or prevent stains on building surfaces. Also see ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES where we describe not only moss and lichens but black fungal stains on asphalt shingles and on other building surfaces.

For an extensive catalog of methods for preventing algae, moss, or lichens growth on roofs see How to Prevent Moss, Lichens & Algae Growth on Roofs. See BLACK STAIN REMOVAL & PREVENTION for advice on diagnosing, cleaning, and preventing algae stains on roofing.

Black stains due to algae: Algae often appears on organic and even inorganic surfaces of buildings and in nature such as on the asphalt roof shingles in this photo.

Black algae stains can also look a lot like extractive bleeding shown in this separate article on "Bleed-Through" which can appear on asphalt roof shingles.

While algae is the most common source of black or green roof stains on shingles, when the staining or bleeding appears to run down the roof from individual small points or "spots" this may be something other than a fungal growth or soot: it may b e extractive bleeding or "bleed through" on shingles. (See ALGAE STAINS ON ASPHALT ROOF SHINGLES and also STAINS on ROOF SHINGLES for a more detailed discussion of bleed through or extractive bleeding as well as black algae stains on roof shingles.)

The presence of algae on the roof is an indicator that this roof area is in a shaded spot where you may want to be alert for development of moss or other roof problems, but the level of damage from algae is probably low, even less than that caused by lichens.

Avoid any aggressive cleaning methods that might damage the roof surface.

Algae stains on concrete (C) Daniel Friedman

Green stains due to algae: green stains also appear on buildings including on shingles, siding, and even on masonry walls, sidewalks, planters, and retaining walls: stone, concrete block, and concrete.

If you see flat green stain on a building exterior and that is not producing any plant-like raised growth it is likely to be an algae.

Watch out: on walks and decks algae makes for a dangerously slippery surface when it is wet. See STONE CLEANING METHODS.

Algae under the microscope has a distinctive appearance that easily distinguishes it from moss, lichens, and mold, as we show here.

This microphotograph of algae was made in our lab while examining a sample sent to us from our friend and mold lab expert Sue Flappan.

The original algae sample was collected from a concrete sidewalk using simple adhesive tape.

What does Lichens look like on buildings, in nature, and in the microscope?

Lichens, one of the most hardy growth organisms found in nature, can grow in harsh conditions. Lichens is often found growing on roof shingles, especially asphalt and wood shingles as we show here.

Photograph of lichens growth on asphalt shingles (C) Daniel Friedman

Our photographs (above) show lichens growing on an asphalt roof shingle in situ (above left). In the photo where our pen is inserted for scale (above right) we had "picked" the spot of lichens gently and flipped it over. Our pen points to the hole left in the asphalt shingle as the lichens had such a good grip on the mineral granules that when removing the lichens it brought some of the roof protective coating along with itself. If you click to enlarge the photo at above right you'll see the actual mineral granules from the shingle adhered in the "roots" of the lichens.

See Lichens on Roofs for details about the causes, effects, and prevention of lichens growth on roofing surfaces. Also see Lichens on Stone Surfaces.

What does Moss look like on buildings, in nature, and in the microscope?

Moss growing on any roof surface will be more severe on roof sections that area shaded and exposed to periodically damp cool weather conditions.

The presence or absence of much sunlight on a roof surface is often a determining factor in the amount of moss or lichens growth (more sun, less moss and lichens.

Moss and lichens are more than a cosmetic issue on many kinds of roofing materials - asphalt shingles, roll roofing, wood shingle roofs, wood shake roofs. By holding moisture against the roof surface lichens but more so moss speed the wear of the asphalt shingle surface in freezing climates by increasing frost damage to the mineral granule coating on the shingles.

Moss under the microscope (C) Daniel Friedman

What Moss Looks Like Under the Microscope - photos

It's easy to see the plant-like structure of moss fragments, as our photograph (left) demonstrates.

This moss sample was collected from a basement wall: we suspect that the damp conditions that produced this moss growth on the building wall also increased the risk of a mold problem in the same structure.

For an identification guide to mosses we include some resources below.

For an extensive catalog of methods for preventing algae, moss, or lichens growth on roofs see How to Prevent Moss, Lichens & Algae Growth on Roofs.

See Black Stain Removal & Prevention for advice on diagnosing, cleaning, and preventing algae stains on roofing.

Online Guide to Types of Stains on Building Surfaces:

In the following guide we list types of stains by stain color & appearance, by building location or material, and by stain cause. We distinguish among the following stuff that may stain or be found growing building roofs, walls, or other surfaces, with extra focus on asphalt shingle roofs as well as other roofing materials such as wood shingles, wood shakes, roll roofing, and even slate or tile roofs. Some of these types of roof stains or discoloration are only cosmetic in nature, while others may indicate growths that are likely to reduce the roof covering life.

A more detailed, illustrated version of the list below is given at STAIN DIAGNOSIS on BUILDING EXTERIORS.

Algae-caused black or green stains on roof or other building surfaces - Some photos of black algae stains are at Black Algae Stains on Asphalt Shingles. For details on roof algae see ALGAE STAINS ON ASPHALT ROOF SHINGLES, and ALGAE STAIN TEST METHODS. Algae can produce black stains on asphalt roofing products. Also see ALGAE, FUNGUS, LICHENS, MOSS COMPARED. And see STAIN DIAGNOSIS on STONE for examples of algae staining on other building surfaces.
Black stains on asphalt roofing products such as asphalt shingles or roll roofing, caused by extractive bleeding (product defects) - see Bleed-Through and see Roofing material defect / environmentally-caused roof shingle stains.
Black, brown, or gray stains on roofing products due to debris left on the roof surface, such as piles of leaves and organic waste from nearby trees. See Debris Staining and see Proximate cause roof shingle stains
Black or other colored stains on roof surfaces may be caused by soot from chimneys, both wood-fired and oil-fired devices. Black or other colored stains may also appear on roof surfaces from nearby industrial activities. See Soot Staining.
Black stains on building interiors: such as on carpets, drywall, or trim: see STAIN DIAGNOSIS on BUILDING INTERIORS and then STAIN DIAGNOSIS on BUILDING INTERIORS and also see STAINS on INDOOR SURFACES: PHOTO GUIDE
Brown or red stains on roof surfaces are often caused by rust from wearing steel flashing or other on-roof metal products. See Rust Stains on Shingles.
Catalog of Biological Substances that Alter Stone or Other Inorganic Materials lists the causes and types of damage that raise aesthetic and conservation issues on cultural artifacts, buildings, and art works.
Chimney stains on roofs - see see SOOT STAINING - Black Soot Stains on Roof Shingles Around Chimneys and see Proximate cause roof shingle stains
Debris stains on roof shingles - see Debris Staining - Black Debris Stains on Asphalt Shingle Roofs
Extractive bleeding stains on asphalt roofs - see Bleed-Through and see Roofing material defect, and see Proximate cause roof shingle stains (types of roof stain by color, location, probable cause)
Green roof stains on roof shingles, clay tiles, cement tiles, and asbestos cement roof shingles or newer fiber cement roof shingles are often caused by algae. For details see ALGAE STAINS ON ASPHALT ROOF SHINGLES. Moss on roofs is also often green and should be unmistakable in appearance. See ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES.
Lichens growing on building surfaces - Lichens are not the same growths as moss or algae, and are difficult to remove without damaging the roof surface. See Lichens on Stone Surfaces, and also see Lichens on Roofs for details about how lichens can cause roof damage. See Methods for Cleaning Stone Surfaces and ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES for a guide to preventing lichen growth and stains. Also see ALGAE, FUNGUS, LICHENS, MOSS COMPARED for an explanation of the difference among these.
Mold or fungus growing on roof surfaces or on other building surfaces - see ALGAE STAINS ON ASPHALT ROOF SHINGLES. See FIND MOLD in buildings, HOW TO for a guide to looking for mold contamination in or on buildings, and see WHAT MOLD LOOKS LIKE for a guide to just what mold looks like on building surfaces. Be sure also to see Stuff that is Mistaken for Mold to avoid becoming excited about harmless substances that people think are toxic mold. If you know your building has a mold problem, see ACTION GUIDE - WHAT TO DO ABOUT INDOOR MOLD.
Moss on roofs and other building surfaces: see ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES, and Green Stains on Stone. Green or other colored mosses are a bit easier to remove than lichens on roofing surfaces, but both can carry away mineral granules and damage the roof surface. Moss tends to hold more water and moisture on the roof surface. So in our opinion moss is more likely to damage a roof surface than lichens or algae. Also see ALGAE, FUNGUS, LICHENS, MOSS COMPARED.
Rust Stains on buildings - see Rust Staining - Red or Brown Rust Stains (on shingles)
Soot or Creosote black or brown stains on roof surfaces near or below chimneys - see SOOT STAINING - Black Soot Stains on Roof Shingles Around Chimneys and see Proximate cause roof shingle stains
Stains on stone or masonry surfaces - see STONE CLEANING METHODS for cause, cure, and prevention
Tree-caused stains on roofs - see Proximate cause roof shingle stains
White stains on roof surfaces may be from wash-down of pigments in paint on surfaces above the roof such as a gable end or dormer wall; white or less-black roof surfaces may also be found below copper or aluminum flashing whose salts run down the roof surface in wet weather, preventing algae or moss growth and leaving a white area on an otherwise stained roof surface. Our article at ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES includes a photograph of this condition on a wood shingle roof.

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ROOFING INSPECTION & REPAIR
  ALGAE STAINS ON ASPHALT ROOF SHINGLES
  ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES
  STAINS on ROOF SHINGLES

STAIN & BIODETERIORATION AGENT CATALOG
STAINS on buildings - QUICK GUIDE
STAIN DIAGNOSIS on BUILDING EXTERIORS
STAIN DIAGNOSIS on BUILDING INTERIORS
STAIN DIAGNOSIS on ROOFS
STAIN DIAGNOSIS on STONE

ALGAE, FUNGUS, LICHENS, MOSS COMPARED

STAIN & BIODETERIORATION AGENT CATALOG
STAINS on buildings - QUICK GUIDE
STAIN DIAGNOSIS on BUILDING EXTERIORS
STAIN DIAGNOSIS on BUILDING INTERIORS
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
  Bleed-Through
  Chimney-Caused Roof Stains
  Debris Staining on Roofs
  Lichens on Roofs
  Moss on Roofs
  Power Washing Roofs
  Rust Stains on Shingles
  Soot Staining

Guides to identifying mosses, lichens, algae
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
Also see the sources listed at worldofmosses.com/ggom/ggomBibliography.html
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
The Ecology of Algae, F.E. Round, Cambridge University Press, 1984 ISBN-10: 0521269067 ISBN-13: 978-0521269063 (Available at Amazon.com)
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.
Lichens of North America, Irwin M. Brodo, Yale University Press, 2001, ISBN-10: 0300082495, # ISBN-13: 978-0300082494 (Available at Amazon.com)
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

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What does Algae look like on buildings and under the microscope?

What does Lichens look like on buildings, in nature, and in the microscope?

What does Moss look like on buildings, in nature, and in the microscope?

What Moss Looks Like Under the Microscope - photos

Online Guide to Types of Stains on Building Surfaces:

Questions & Answers regarding this article

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