Stains & discoloration on brick surfaces:

This article describes the causes & cures for various types of stains found on brick surfaces both outdoors and indoors. We list the common sources of stains on brick chimneys, walls, walks, and ceilings.

The article distinguishes among common brick stain sources such as algae, bacteria, lichens, moss, soot, sulphur, fungal growth, and other causes of markings on brick.

Stains on Brick Surfaces

Article Contents

• STAINS on BRICK SURFACES
  • BRICK CHIMNEY STAINS
  • BRICK EXTERIOR WALL STAINS
  • BLACK STAINS on BRICK
  • GREEN STAINS on BRICK - ALGAE
  • RED STAINS on BRICK - RUST?
  • WHITE STAINS on BRICK
  • BRICK EXTERIOR CLEANING WARNINGS
  • BRICK EXTERIOR PATIO / WALK STAINS
  • BRICK INTERIOR WALL STAINS
  • BRICK SURFACE PAINT REMOVAL
  • BRICK STAIN REMOVAL GUIDES

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Photo above, brick (and stone) staining in the dungeon at Goodrich Castle, Ross on Wye, Herefordshire, England, UK.

Brick Chimney Stains

Below our photograph at left shows white gunk on the exterior surface of a chimney.

This is almost certainly efflorescence, a mineral salt left behind as water leaks into and evaporates out of the brick chimney.

The next photo (below) shows black soot staining at the top and sides of a brick chimney. If this soot is from an oil fired heating appliance, a service call is needed.

[Click to enlarge any image]

See EFFLORESCENCE SALTS & WHITE DEPOSITS for steps to cure efflorescence and to remove it from brick or other masonry surfaces.

Below we see black or brown tarry stains on the surface of a chimney visible in an attic.

These are most likely creosote, or creosote mixed with soot that has leaked through openings in this antique brick chimney and its flue. We discuss this chimney and what to do about it

at CHIMNEY STAINS, INDOORS

See CHIMNEY STAINS & LEAKS for a catalog of stains appearing on, in or around all types of chimneys.

Watch out: water damage or soot, creosote, or other blockages of chimneys may make the chimney or flue unsafe.

See CHIMNEY INSPECTION DIAGNOSIS REPAIR

Stains on Brick Exterior Walls

Black, dark, or green stains on exterior brick

A reader asked us for an opinion of the cause of the green and black stains on this exterior brick building wall.

While a closer on-site inspection or in some cases a forensic lab analysis of a tape lift of the brick wall surface would be needed for certain identification, this looks much like black and green algae growing on the wall surface.

The reader noted that the dark staining on this brick was occurring only below an area where roof drainage was spilling down the building wall, and s/he asked for advice about how to clean this surface, and whether power-washing would be ok.

To minimize the chances of damage, we like to start cleaning with the most gentle approach first to see if that's sufficient.

Power washing may be OK on this modern hard-fired clay brick wall as long as the washer does not spray water into the wall cavity through weep holes or other openings.

More black stains on an exterior brick wall are shown just below. These are due to rain-splash-up from the lower roof onto the brick sidewall. The increased moisture level has encouraged algal growth on the brick surface.

Green Stains on Exterior Brick Walls: Algae

Above the green stains on this structural brick wall (Vassar College, Poughkeepsie, New York, USA) are almost certainly an algae growth.

The wall is shaded and roof drainage system leaks have made this wall side particularly wet. Later, after the roof drainage system had been repaired, this wall was renovated and portions of it that had been frost-damaged were re-built.

Common Causes of Green Stains on Brick Surfaces

• Algae, Lichens, Moss on brick
• Green paint
  
  on brick: identify as pant from nearby surfaces or building history
• Vanadium salt staining
  
  on brick: vanadium salts combined with acidic environments that may in turn be due to use of muriatic acid or HCL to clean brick surfaces or in areas of acid rain can leave greenish crystalline salts on the brick surface. Stain may be chartreuse in colour, green, or yellowish-green.
  
  Remove vanadium green stains:
  
  using chemical cleaners such as VanGo, Oxcid (followed by a neutralizing agent such as Neutril) IF the staining was not due to use of an acidic cleaner as we mention above;
  
  Wallkleen may also work.
  
  Laser cleaning of moulds and rusts and oxides can work on artifacts but may not be cost-effective for buildings.
  
  Oxcid or Vital Oxide cleaner, various sources [citations needed]
  
  VanGo, from ATCO International, 1401 Barclay Circle, SE Marietta, Georgia 30060-2925 produces a series of cleaners and paint and graffiti removers. 1-800-723-2826 Website: https://www.atcointernational.com/prod-22-1-663-24/vango-ii.htm
  
  Walkleen, from Sanosil, active foam cleaner, is an acidic facade cleaner. Sanosil A.G., Eichtalstrasse 49 CH-8634 Hombrechtikon Website https://www.sanosil.com/en/produkte/wallclean-s-fassadenreiniger-sauer/ excerpt:
  
  Sanosil WallClean S is a powerful special active foam cleaner for pre-treating or cleaning façade surfaces infested with mould, algae or moss.
  
  Sanosil WallClean S does not contain any fungicides and is completely biodegradable in accordance with European directive 73/404/EEC relating to detergents and directive 73/405/EEC on biodegradability testing.
  
  Sanosil WallClean S effectively removes oil and grease, limescale, wax residue, algae and plant components, and soiling (mud, dust etc.). Particularly suitable for use as an active foam in conjunction with low-pressure foam applicators.

Question: why is my brick wall mortar turning green & what can I do about it

Can you please advise what I should do about my new garden wall? The mortar is starting to turn green. - Anonymous by private email 2021/03/31

Moderator reply: how to clean & prevent algae growth on brick walls

The green in your photos is almost certainly algae, though there could be some mold growing there too.

The algae growth occurs "naturally" outdoors on wet masonry (and other surfaces), particularly in a damp or wet climate and more-so where shaded from sun exposure. 

You can clean the algae using any of several cleaners that are discussed

at BRICK STAIN REMOVAL GUIDES

and also

at STONE, STUCCO & BRICK CLEANING METHODS - where there are also some prevention suggestions. 

Also see ALGAE & MOLD STAINS on EXTERIORS

A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer  than we can give by email alone. You will find additional depth and detail in articles at this website. 

Red Stains on Brick: Rust?

On 2018-09-16 1 by (mod) - diagnose and remove red stains on brick window sill

Mahmood

Regarding the dark red stains on the center of the brick window sill in your photo:

My best guess is that previously someone had a window air conditioner in the window in your photo and the A/C condensate rusted the air conditioner base and stained the brick as it drooled down the building wall.

If the red stains on the brick sill are from rust, try an iron or rust stain remover product.

The article STAINS on BRICK SURFACES discusses approaches to cleaning stains on brick as well as preventing their recurrence.

If the red stains on the brick sill in your photo are algae (which seems less likely given the circumstances portrayed in your photo, but still, not impossible), just about any household cleaner may remove it; use plenty of rinse water to avoid any bleach staining of the bricks below.

Sources of Red Stains in or on Brick Surfaces (also black & brown)

• Manganese dioxide (MnO₂) efflorescence:
  
  manganese dioxide inclusions in the brick (or mortar) may be dissolved by very soft rainwater or by use of muriatic acid (often used to clean mortar from brick surfaces after recent masonry work). The alkaline chemistry of mortar may react with MnO₂ to form a brownish-red stain or or sometimes a black stain on brick.
  
  Remove using a dilute acid such as 0.01M Hydrochloric Acid (HCL) and 3% Hydrogen Peroxide H₂O₂. Rinse thoroughly, promptly to avoid run-down stains.
  
  Cream of tartar + hydrogen peroxide may also work.
• Red algae, lichens, mold stains:
  
  some algae (and some fungi or lichens) are red in colour; correlate with moisture and shade.
  
  Remove from brick using soft brush scrubbing (avoid power-washing that may damage brickwork) and any household cleaner or deck cleaner. Rinse thoroughly, promptly to avoid run-down stains.
• Rusting metal components or hardware above the stain area
  
  such as iron window frames, failing galvanized iron flashings, hardware such as shutter bolts or metal fixtures, even iron or cast-iron piping, railings, etc. above or near the brick surface.
  
  Remove from brick using an iron stain remover product. Rinse thoroughly, promptly to avoid run-down stains.

• Rusting metal reinforcement
  
  in brick walls and chimneys such as iron wire, mesh, or re-bar too close to the surface of a mortar joint
  
  Remove from brick using an iron stain remover product. Rinse thoroughly, promptly to avoid run-down stains. Re-mortar open joints after sealing the exposed metal with a masonry-compatible bonding/agent or sealer or primer.
• Iron sulfide pyrrhotite inclusions
  
  in some bricks.
  
  Remove from brick using an iron stain remover product. Rinse thoroughly, promptly to avoid run-down stains.
  
  Re-mortar open joints after sealing the exposed metal with a masonry-compatible bonding/agent or sealer or primer. - Doubtful that this will provide long term success. Contaminated brickwork may need to be removed and replaced.

Other brick surface cleaners that might work:

• Paste of dish soap or borax or TSP substitute and salt, 10 -30 minute exposure, rinse thoroughly.

Also see research on red stains on buildings and red stain and iron stain removal suggestions found in these InspectApedia articles

FOUNDATION DAMAGE by MATERIAL or INCLUSIONS - red stains caused by inclusions of iron sulfide mineral (pyrrhotite) can appear in concrete and in some brick and stone materials.

RUST STAINS on ROOFS - examples of red rust stains from oxidizing corroding metal

STAINS on STONE, STUCCO DIAGNOSE & CURE - additional cleaning methods that can work on brick

WATER SOFTENER IRON & SEDIMENT REMOVAL - more rust stain remover products

On 2018-09-15 by Mahmood - what caused and what will remove these red stains on brick?

Our outer Brick walls few bricks stained along with window glass from outside due continuously dripping of A/C water. Kindly advice and help how to clean stains from bricks and glass.

The photo is shown above.

White Stains on Brick Walls: Efflorescence vs. Paint Pigment Run-down vs. Mortar SNAFUs

Earlier we illustrated white efflorescence staining on a brick chimney, a common spot where efflorescence appears outdoors on masonry buildings.

Our photo above, showing thick white deposits on a structural brick wall in New York (Vassar College) shows that efflorescence can show up anywhere that there are water leaks in or down brick walls.

See EFFLORESCENCE SALTS & WHITE DEPOSITS

But not all white stains on brick surfaces are due to efflorescence

Above the white stains on this brick veneer wall were caused by leaks into the white coated aluminum soffit. White pigment from the soffit has run down the wall leaving a white deposit. There was a bit of green algae in the top area of this stain too.

Really? Brick veneer? Yes.

Before you write to gripe that the small brick-ends indicate a bond course making this a structural brick wall let me explain that no, this is a brick veneer wall constructed by a retired mason who took delight in making it look like a structural wall.

The wall is actually a single wythe brick veneer fastened to a concrete block structural wall.

Below we illustrate another white area on a brick wall that is not due to water or leakage nor to paint pigment wash-down. .

The white "stains" on the brick exterior wall shown above are not stains at all but rather mismatched mortar used by a mason or an amateur who had little concern for preserving this pre-1900 home in Dutchess County, New York.

The bricks in this wall were already spalling but the use of a harder mortar for the repair work is likely to accelerate the spalling damage to this home located in a freezing climate.

Question: are these white stains on brick efflorescence?

Please see attached picture.

Is this efflorescence?

Is this the result of run off water from the exterior shutters?

I noted that similar staining on brick surfaces on inspectapedia and it was recommended to use a TSP (equivalent) cleaning solution would you recommend that here too?

Thinking of recommending professional cleaning.

• Dov Ber Kahn, a home inspector in Rockland County, NY has contributed photographs of various building features. Mr. Kahn is a licensed home inspector in New York and New Jersey, and can be reached at Website: Kahnbhomeinspectors, Tel: 845-445-8234, Email: kdovber@googlemail.com

Moderator reply: white paint pigment - oxidized paint runs down onto & stains brick veneer

Notice the pattern of white staining is most notable immediately below the edges of those white-painted shutter?

Most-likely it's white paint pigment runoff from the shutters.

There are some whitish bricks that may each be producing their own personal patch of efflorescence - take a closer look at

 

Brick wall stain removal by cleaning, power washing, sand-blasting: warnings

Watch out: Experts like Grimm (1990) widely warn against sand-blasting to clean brick surfaces of buildings. That aggressive approach damages the brick and mortar and can lead to rapid deterioration of the wall.

Furthermore, on antique, soft brick, even power washing can remove the brick's harder-fired surface, leaving the softer brick interior vulnerable to water and frost damage and causing costly building damage.

Power washing can also remove older soft mortars. And even on the modern hard clay brick wall, the washer needs to be used with care, starting from a more distant position in order to avoid leaving too-light power-sprayer marks on the wall.

Extra care must be taken if cleaning a brick-veneer wall as there may be more weep openings or leaks around window or door penetrations through which water may be inadvertently sprayed into the wall cavity.

Other brick wall cleaning methods such as using lasers, photocatalytics, or special cleaners are discussed both at
theReferences or Citations for this article

and
at STONE, STUCCO & BRICK CLEANING METHODS

Stains on Exterior Brick Floors, Patios, Walks

At below left the black stains on this exterior brick patio located in New York state are probably algae but might also be a fungus. We'd need to examine a sample in the lab. At below right we see moss growth on the same brick patio in a nearby area.

This is a shaded brick patio constructed in the late 1990's. As plantings grew and a shade tree's canopy began to keep more of the patio area in shade in summer months the area covered by algae, moss, and possibly fungi has grown.

Remedies to reduce the staining on the brick shown above include assuring proper drainage, increasing the sun exposure by judicious pruning, sweeping off organic debris that hold water on the surfaces (leaves), and occasional power-washing.

Watch out: algae and moss on a brick walking surface or on any walking surface for that matter, are very slippery and risk a slip-trip-fall injury.

See SLIPPERY STAIRS, WALKS, ROOFS for the static coefficient of friction of various slippery walking surfaces.

Below we illustrate outdoor brick patio or walk surfaces that are not slippery with algae, moss, fungi.

Below we illustrate that a brick walkway, even one built using antique bricks that have been in place for more than 50 years do not have to be slippery with algae, moss, nor fungi.

The Dutchess County New York brick walkway shown above is in a sunny area and is well drained.

However the property manager does need to keep alert for frost-heaved or broken bricks that might form a trip hazard.

Stains on Interior Brick Wall, Ceiling, or Floor Surfaces

Above at left, notice the dark stains on the rear wall and white efflorescence stains on the ceiling of the dungeon at Goodrich Castle, Ross on Wye, Herefordshire, England, UK.

Both of these stain sets can be ascribed to water entry, but we also observed moss and even some fungi growing on these walls.

Below are very black creosote and soot stains on the hearth-face of a stone fireplace installed in a hand-built log cabin at Elk Lake Michigan.

Also see STAINS on INDOOR SURFACES, PHOTO GUIDE.

Finding and fixing leaks into or onto brick structures is a key step in stopping the formation of algae, moss, efflorescence, or fungal staining on brick surfaces.

How to Remove Paint from Brick or Stone Surfaces

Here is a summary of good practices when you need to remove any type of paint from an exterior or interior brick wall, fireplace, or other surface. These methods also work well for stone surfaces.

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Question: How do I clean off paint run-down from white siding on brick

1 June 2016 dennis said:
how do i clean paint pigment run down from white siding on brick

Reply:

Dennis,

How to Remove Paint Chalk Rundown from Brick Surfaces

If you are asking only about the simple deposits of runoff from a chalking painted surface, I recommend gentle cleaning of the brick with a natural bristle brush and a TSP substitute cleaning solution.

You can also try household detergent. Please see our warnings below about the dangers of aggressive cleaning or power washing of brick surfaces.

Don't waste time trying bleach as some of our readers did. Bleach won't remove white paint pigment and bleach itself, running down building surfaces can leave white streaks if not washed-off quickly enough.

How to Remove Actual Paint or other Coatings from Brick Surfaces

Before starting, for best results in brick surface cleaning you need to know

1. The kind of paint you want to remove,
   
   as paint chemistry defines what solvents work best on it - latex is different from alkyd or old oil-based paint.
   
   I experiment with soap and water, mild cleaners such as vinegar, even dish soap or TSP substitute, and for some paints I might try lacquer thinner, odorless paint thinner, and peel-away paint stripping coatings.
   
   In the photo above we see thick black coating on part of a brick exterior wall of a Vassar Farm building in Poughkeepsie, NY, USA.
   
   This is tar, not paint. Most paint removal treatments will just make a mess on this surface.
2. The amount of paint to be removed,
   
   as a small scale cleaning project may take a different approach from cleaning an entire brick (or stone) surface that has been painted over.
   
   A large area project is going to require drop cloths, protective gear, and probably two stages of chemical stripping followed by gentle brush and wash cleaning of the brick surface.
3. The nature of the brick (or stone) surface 
   
   - as glazed brick or hard stone is easier to clean with solvent while soft brick or soft stone such as brownstone or sandstone are at risk of absorbing solvent-borne pigments.
   
   Soft brick and mortar also absorb more water and are at greater risk of frost damage if soaked right before freezing weather.

So I don't think there is a single "right" answer that's optimum for all conditions.

Brick Cleaning Mistakes to Avoid

Watch out: For people who are going to jump to "how to" let's first warn off some mistakes that you'll regret:

• I'd avoid power blasting 
  
  brick with sand or grit as that damages the brick, and even power washing with water can damage some brick and some mortar.
  
  Blasting or power washing can remove the glazed surface of brick thus causing it to deteriorate rapidly from subsequent rain and in cold climates frost. Much has been written warning about too-aggressive cleaning methods on historic or older buildings, as you'll see in our citations below.
  
  The badly-spalling wall of this Brooklyn NY building may have been damaged by sandblasting.
• I'd be careful to experiment with solvents 
  
  before making a mess on the surface.
  
  I scrape off thick coatings with a sharp scraper, then try scrubbing small areas of run-down with a toothbrush, rinsing liberally and frequently before the solvent borne paint soaks into the surrounding brick.
• Cold weather warning:
  
  I avoid soaking brick and mortar with water or starting any paint removal project when freezing weather is imminent, so now in the spring (if you're north of the equator) is a good time to scrub the surface using a stiff brush and the mildest solvent that works on the paint.
• I also avoid muriatic acid 
  
  as it's not a good paint solvent (and is dangerous to work-with). Muriatic acid is good for cleaning mortar from brick or stone surfaces as a last step when repairing or re-pointing masonry.
• Bottom line objective 
  
  when removing paint from brick: avoid damaging the brick such as by removing a hard glazed surface, avoid using very volatile solvents that carry pigment into the brick surface, and be very careful about personal protection from chemicals, lead, dust, etc.
  
  Test your stripping or cleaning procedure in a small, less-obvious area before tackling the main painted brick area.

Recommended Paint Removers or Cleaners or Strippers for Brick or Stone Surfaces

Choose a paint removal method that suits the amount of paint, type of paint, and condition of the brick or stone itself. A peel away paint remover may also work on some masonry surfaces.

Try Citri-Strip for a less-toxic cleaner that may work on your paint. Newer peel-away chemical paint remover systems that use a fabric + thick paint-on chemical paste can pull paint off of the brick.

1. Prepare the work site:
   
   Put down 6-mil poly to catch paint and drippings safely while avoiding contaminating soil below the wall.
2. Prepare the workers:
   
   Wear protective gear appropriate for the chemicals used.
   
   Some paint stripping chemicals are carcinogenic, some can cause dangerous burns or eye damage, some produce harmful VOCs and may require use of a respirator.
   
   Old paints contain lead that can poison workers who don't protect against dust or fumes.
3. Apply the strip or cleaning solution.
   
   If you are using a peel away method, basically you put down drop cloth, coat the surface, apply fabric strips, wait, peel away the fabric that carries away most of the paint.
4. Final cleanup:
   
   Wash / clean the brick surface after the main body of paint has been removed. Even after using the paint stripper you will probably have to do some additional gentle scrubbing on the brick surface as some pigment may remain.
5. Dispose of waste:
   
   Read the disposal recommendations from the manufacturer of the chemical or paint stripper you are using before starting the job. Lead paint chips or debris may also require special handling, wrapping, disposal.

Take a look at some of the brick cleaning references I will cite below, especially work where Grimmer was involved.

Guides for Removing Paint & Stains from Brick Block or Stone Surfaces

• STONE, STUCCO & BRICK CLEANING METHODS [web article] DIY cleaning methods for masonry surfaces, at InspectApedia.com
• Ashurst, Nicola. Cleaning Historic Buildings: V. 2: Cleaning Materials and Processes. Routledge, 2015.
• Beloin, Norman J., and Fred H. Haynie. "Soiling of building materials." Journal of the Air Pollution Control Association 25, no. 4 (1975): 399-403.
• Brocken, Harold, and Timo G. Nijland. "White efflorescence on brick masonry and concrete masonry blocks, with special emphasis on sulfate efflorescence on concrete blocks." Construction and Building Materials 18, no. 5 (2004): 315-323.
• Brick Industry Association (BIA), CLEANING BRICKWORK [PDF] in Technical Notes on Brick Construction, August 2018, BIA 12007 Sunrise Valley Drive, Suite 430, Reston, Virginia 20191 USA retrieved 2019/08/16, original source: http://www.gobrick.com/docs/default-source/read-research-documents/technicalnotes/20-cleaning-brickwork.pdf www.gobrick.com | 703-620-0010
• Brick Institute of America. "Cleaning Brick Masonry." Technical Notes on Brick Construction (No. 20) rev., November, 1990.
• Bryant, Terry. "Protecting Exterior Masonry from Water Damage: Moisture Control Procedures & Products." Technology & Conservation, Spring 1978, pp. 38-42.
• The Masonry Institute of America - https://www.masonryinstitute.org/
• Cotton, J. Randall. "Blasted... Now What?" The Old-House Journal, January/February 1987, pp. 38-41.
• Daniels, Alva E., John R. Kominsky, and Patrick J. Clark. "Evaluation of two lead-based paint removal and waste stabilization technology combinations on typical exterior surfaces." Journal of hazardous materials 87, no. 1 (2001): 117-126.
• 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.
• Grimm, Clayford T. REMOVING STAINS from BRICK [PDF] Mag. Masonry Constr. 3, no. 3 (1990): 117-121.
• Grimm, Clayford T. "Don’t sandblast brick." The Magazine of Masonry Construction (1990): 115-116.
  
• 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.
  
  Excerpt:
  Abrasive cleaning methods are responsible for causing a great deal of damage to historic building materials.
  
  To prevent indiscriminate use of these potentially harmful techniques, this brief has been prepared to explain abrasive cleaning methods, how they can be physically and aesthetically destructive to historic building materials, and why they generally are not acceptable preservation treatments for historic structures.
  
  There are alternative, less harsh means of cleaning and removing paint and stains from historic buildings.
  
  However, careful testing should precede general cleaning to assure that the method selected will not have an adverse effect on the building materials.
  
  A historic building is irreplaceable, and should be cleaned using only the "gentlest means possible" to best preserve it.
• 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.
• 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.
• Hocken, Jörg, and Bernd Proft. "Clean surfaces by utilization of the photocatalytic effect." (2003).
• Liu, Katherine, and Elsa Garmire. "Paint removal using lasers." Applied optics 34, no. 21 (1995): 4409-4415.
• Ma, Guang-You, Lin-Yan He, and Xia-Fang Sheng. "Characterization of bacterial community inhabiting the surfaces of weathered bricks of Nanjing Ming city walls." Science of the Total Environment 409, no. 4 (2011): 756-762.
• Mack, Robert C., FAIA & Anne E. Grimmer, ASSESSING CLEANING AND WATER-REPELLENT TREATMENTS FOR HISTORIC MASONRY BUILDINGS [PDF] (2000) U.S. National Park Service, Technical Preservation Services, retrieved 2022/10/02 original source: https://www.nps.gov/tps/how-to-preserve/briefs/1-cleaning-water-repellent.htm
  
  Excerpt: Inappropriate cleaning and coating treatments are a major cause of damage to historic masonry buildings. While either or both treatments may be appropriate in some cases, they can be very destructive to historic masonry if they are not selected carefully.
  
  Historic masonry, as considered here, includes stone, brick, architectural terra cotta, cast stone, concrete and concrete block. It is frequently cleaned because cleaning is equated with improvement. Cleaning may sometimes be followed by the application of a water-repellent coating.
  
  However, unless these procedures are carried out under the guidance and supervision of an architectural conservator, they may result in irrevocable damage to the historic resource.
• Mack, Roberty C., FAIA & John P. Speweik, REPOINTING MORTAR JOINTS IN HISTORIC MASONRY BUILDINGS [PDF] (1998) U.S. National Park Service, Technical Preservation Services, retrieved 2022/10/02 original source: https://www.nps.gov/tps/how-to-preserve/briefs/2-repoint-mortar-joints.htm
  
  Excerpt:
  
  Repointing, also known simply as "pointing"or—somewhat inaccurately—"tuck pointing"*, is the process of removing deteriorated mortar from the joints of a masonry wall and replacing it with new mortar.
  
  Properly done, repointing restores the visual and physical integrity of the masonry. Improperly done, repointing not only detracts from the appearance of the building, but may also cause physical damage to the masonry units themselves.
• 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.
• Rozniakowski, Kazimierz, Piotr Klemm, and Agnieszka J. Klemm. "Some experimental results of laser beam interaction with surface layer of brick." Building and Environment 36, no. 4 (2001): 485-491.
• Shahidi, Salman, Stéphane Mérillou, and Djamchid Ghazanfarpour. "Phenomenological simulation of efflorescence in brick constructions." In Proceedings of the First Eurographics conference on Natural Phenomena, pp. 17-23. Eurographics Association, 2005.
• Tiller, Teel Patterson, THE PRESERVATION OF HISTORIC GLAZED ARCHITECTURAL TERRA-COTTA [PDF] (1979) Preservation Brief No. 7, U.S. National Park Service, Technical Preservation Services, retrieved 2022/10/02 original source: https://www.nps.gov/tps/how-to-preserve/briefs/7-terra-cotta.htm
  
  
• U.S. GSA REMOVING BIOLOGICAL GROWTH FROM EXTERIOR MASONRY AND STUCCO [PDF] (2018) U.S. General Services Administration, retrieved 2020/12/14
  
  Excerpt: This procedure includes guidance on removing biological growth such as lichens, algae, mold and mildew from masonry and stucco. B. Biological growths such as lichens, algae, moss and fungi growing on masonry walls is usually an indication that there is excess moisture in or around the masonry.
  
  These growths should be removed, as they attract moisture to the masonry surface and hold it there, which can lead to more serious problems. Lichens and mosses in particular, produce oxalic acid which can damage certain types of historic masonry.
• US GSA Removing [BROWN] Manganese STAINS from BRICK MASONRY [PDF] U.S. General Services Administration, retrieved 2020/12/14
• U.S. GSA REMOVING CLIMBING PLANTS AND CREEPERS FROM MASONRY [PDF] (2018) U.S. General Services Administration, retrieved 2020/12/14
  Excerpt:
  
  This procedure includes guidance on removing climbing plants from masonry.
  
  It is important to remove heavy vegetative growth from masonry, as its presence can pose many problems, such as holding moisture against the masonry surface, blocking gutters and downspouts, scouring soft wall surfaces, eroding mortar and hindering or limiting access for maintenance inspections and repairs.
• US GSA Removing SMOKE STAINS From BRICK MASONRY [PDF] U.S. General Services Administration, retrieved 2020/12/14
• US GSA Removing [YELLOW GREEN] Vanadium STAINS From BRICK MASONRY [PDF] U.S. General Services Administration, retrieved 2020/12/14
  Excerpt:
  
  This procedure includes guidance on removing yellow or green stains from brick masonry resulting from deposits of vanadium salts on the masonry surface. B. Vanadium staining is a form of efflorescence that originates in the raw material used to manufacture certain brick units.
  
  It develops when moisture in the wall draws salts and color from the brick composition to the surface of the masonry. As the water evaporates, vanadium staining is left behind.
• US GSA REMOVING DIRT from BRICK MASONRY [PDF] U.S. General Services Administration, retrieved 2020/12/14
• US GSA CHEMICALLY REMOVING PAINT FROM and REPAINTING BRICK MASONRY [PDF] U.S. General Services Administration, retrieved 2020/12/14
  Excerpt:
  
  This procedure includes guidance on chemically removing paint from and repainting brick masonry.
  
  NOTE: Sandblasting is not recommended by the secretary of the interior's standards for rehabilitation and shall not be used. High-pressure water blasting is also not recommended without adequate testing or experience as it may erode soft brick and drive moisture into the wall.
• US GSA GENERAL CLEANING of EXTERIOR BRICK MASONRY [PDF] U.S. General Services Administration, retrieved 2020/12/14
  Excerpt:
  The work specified herein requires knowledge of older materials and methods and a high degree of skill to execute properly. This work should be performed only by an experienced, pre-qualified contractor. It is not recommended that building maintenance personnel perform this work.
• US GSA POULTICING COPPER/BRONZE STAINS FROM BRICK MASONRY [PDF] U.S. General Services Administration, retrieved 2020/12/14
• US GSA POULTICING RUST STAINS FROM LIMESTONE AND MARBLE [PDF] U.S. General Services Administration, retrieved 2020/12/14
  Excerpts:
  
  This procedure includes guidance on removing rust stains from limestone and marble by poulticing using different chemical solvents or by using a paste containing a commercial rust remover.
  
  NOTE: THIS PROCEDURE MAY ALSO BE USED FOR REMOVING RUST STAINS FROM BRICK MASONRY.
  
  Metallic stains from iron or steel have the appearance of rust. This type of staining is often caused by the run-off from flashing, gutters, statuary and fasteners.
  
  The source of the rusty runoff should be determined and cause abated. Cleaning should be undertaken after rectifying deficiencies causing the rusting.
• US GSA REMOVING SALTS / EFFLORESCENCE from BRICK & STONE MASONRY [PDF] U.S. General Services Administration, retrieved 2020/12/14 original source: https://www.gsa.gov/ technical-procedures/ making-solution-removing-beverage-soot-tar-and-other-stains-concrete?Form_Load=88552
• US GSA [PDF] U.S. General Services Administration, retrieved 2020/12/14

• U.S. GSA REMOVING COPPER-BASED STAINS FROM BRICK, CONCRETE AND LIMESTONE [PDF] (2018) U.S. General Services Administration, retrieved 2020/12/14
  Excerpt:
  
  This specification provides guidance on removing copper staining on exterior brick, concrete and limestone.
  
  Remove soiling, stains and crusts from the limestone and granite without damaging underlying material and to give all stone a clean, uniform appearance without blotches, streaks or other irregularities. Use the gentlest means to meet the cleaning objective.
  
  If the exterior masonry has been previously subjected to inappropriately harsh and uneven cleaning, it is expected that the cleaning will reveal the original colors and textures of the brick, but that it will not completely correct the differential effects of the previous cleaning.
  
  Clean brick to remove soiling, stains and crusts to the extent feasible without further damaging the brick.
• U.S. GSA REMOVAL OF FERROUS STAINING FROM BRICK, GRANITE, CONCRETE AND LIMESTONE [PDF] (2018) U.S. General Services Administration, retrieved 2020/12/14
  Excerpt:
  
  This procedure includes guidance on removing ferrous staining from exterior brick, concrete and limestone surfaces.
  
  Remove soiling, stains and crusts from the limestone and granite without damaging underlying material and to give all stone a clean, uniform appearance without blotches, streaks or other irregularities. Use the gentlest means to meet the cleaning objective.
  
  If the exterior masonry has been previously subjected to inappropriately harsh and uneven cleaning, it is expected that the cleaning will reveal the original colors and textures of the brick, but that it will not completely correct the differential effects of the previous cleaning.
  
  Clean brick to remove soiling, stains and crusts to the extent feasible without further damaging the brick.
• U.S. GSA REMOVING PAINTED GRAFFITI FROM MASONRY [PDF] (2018) U.S. General Services Administration, retrieved 2020/12/14
  Excerpt:
  
  This procedure includes guidance on removing painted graffiti from historic masonry (this includes spray paint and paint-based felt-tipped markers).
  
  Successful removal of graffiti from masonry is dependent upon the type and surface texture of the masonry as well as the particular substance applied.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2022-04-21 by Inspectapedia Com Moderator - cleaning efflorescence off of brick

@Anonymous,

If that's efflorescence then simple household vinegar will reduce it significantly. Try that followed by a clean water rinse.

On 2022-04-21 by Anonymous

@Inspectapedia Com Moderator,

Hi, thank you so much for the reply. I have not tried a detergent cleaner. Is there a specific method on how to clean these bricks or suggested detergent?

Also do you think behind the brick wall could have water damage causing this? It does look like it's getting lighter(see second image attached - this is what it was at first) ... and we have no water entry on the drywall in the house/insulation on that interior wall.

On 2022-04-19 by Inspectapedia Com Moderator - black algae or mold on brick wall

@James,

I agree that two years ought to be more than enough time for wet brick walls to dry out if the leak is truly fixed.

But water running down a brick wall may leave behind stains formed, for example by algae growing in the wet area.

For the dark brick areas, have you tried a simple detergent cleaner to see if that affects the staining?

Or are you talking about those white areas on the brick - efflorescence?

On 2022-04-19 by James

I had a roof leak about 2 years ago that leaked for a large part of the winter. We fixed the leak and we assumed summer time would dry the brick.

It did get better but still it looks like the brick is wet almost 2 years later. Any ideas on what can be done? Thanks in advance!

On 2022-04-19 by Inspectapedia Com Moderator - brick cleaning products available

@Kimberley,

That's probably soot or dirt washing down onto the upper wall sides from the wall cap-masonry. Try some simple detergent cleaners first. Other brick cleaning products are described in the page above.

Let me know how that works.

On 2022-04-17 by Kimberley

Perhaps you have some input for this photo of mine, how to get rid of the black on this colour of brick?

On 2022-03-23 by Inspectapedia Com Moderator - mold on bricks?

@George,

I can't see any obvious mold on the bricks in your photo. Mold of various genera/species can be found growing on almost any surface but when it's found on stone, brick, concrete, concrete block, I expect that there is a surface coating of either paint or organic dust and debris - some material that's mold-friendly and organic, providing food for the fungus to eat.

So perhaps there is something else on your brick, such as efflorescence or debris, even tar or paint, from having used old, re-cycled brick in construction of the fireplace.

If there is efflorescence you'll want to look for and fix the moisture source such as a chimney leak or missing chimney cap.

See details starting at EFFLORESCENCE SALTS & WHITE DEPOSITS https://inspectapedia.com/Wet_Basements/Efflorescence-White.php

and at

EFFLORESCENCE & BROWN DEPOSITS https://inspectapedia.com/Wet_Basements/Brown_Red_Effloresence.php

On 2022-03-23 by George

We have several bricks on an interior, lower level brick fireplace. We had them treated for mold with no results. I tried bleach and white vinegar with no results. The room is carpeted and heated.

On 2021-10-24 by Anonymous

@inspectapedia.com.moderator, @inspectapedia.com.moderator,

Then
And you very much for your guidance. Vey much appreciated.

On 2021-10-23 by inspectapedia.com.moderator -drying of bricks can take weeks or more

@Mike,

It can take weeks or in some cases even several months of dry and warm weather for watermark bricks to dry out such that you no longer see that dark area in your photo.

As long as it wasn't some chemical or other contaminants look leaks down the wall it's likely that that mark will mostly disappear with time.

I don't see weep holes in what I think is a brick veneer wall. Can I see water stains below the window.

Depending on how much water ran down your wall it's possible that the wall cavity itself as wet and it may be worth exploring the wall cavity from inside the building to be sure that you're not breeding a mold palace.

On 2021-10-23 by Mike

Hi, This is a new wall that got soaked when guttering was disconnected. Doesn’t seem to have dried at all in the last three weeks (October).

Will we be left with a permanent darkened area where the facing brick has absorbed the water? Or is there a likelihood or hope it will dry out eventually in warmer months? Thank you

On 2021-08-29 by inspectapedia.com.moderator

@Rob,

First I'd give the area time to dry, after you've fixed leaks at the sill or window that have let water run behind those bricks. (Remember to look inside for moisture, mold, water damage, insect attack, etc.)

When you're sure the dark area is not simply higher moisture, thus leaving us to guess that we're seeing a fungus or algae, then you can try some of the cleaning methods described at

STONE, STUCCO & BRICK CLEANING METHODS https://inspectapedia.com/exterior/Stone_Cleaning.php

On 2021-08-29 by Rob

Hi I have dark stain below window sill. Cement under sill is cracked and sill is tilted inside. I think stain is caused by water leak. I'm getting sill fixed but wondering how to remove stain from brick. Thanks

On 2021-07-10 by inspectapedia.com.moderator - how to remove black carbon

@Sam firth,

Please see

STONE, STUCCO & BRICK CLEANING METHODS

On 2021-07-09 by Sam firth

How to remove black carbon pollution of stone

On 2021-05-08 by (mod) - variations in brick mortar, color, stains on 100 year old Utrecht building

It would be expected that over its life some of the brickwork on a century-old building has been re-built, particularly over that door lintel, also in areas prone to water damage;

Moisture seeping into brick will often produce a white efflorescence; so we'll see at least three brick colours and may on closer inspection see differences in the mortar mix or even tooling details at the mortar joints - supporting an understanding of the building's history.

Dark brown or black stains I see in an area below the patio wall / flat roof parapet wall are often algae or on occasion, a mold that's invited where there has been extra wetness - perhaps from a leaky parapet capstone covering.

You will want to be sure that there are no leaks into the wall structure particularly from the patio roof above. Very often when we see white stains on brick is efflorescence from moisture. You can read about that in this article series.

[Click to enlarge any image]

On 2021-05-08 by Eva28

The building is in Utrecht, the Netherlands and was built around 1900-1920. Indeed the top left corner seems as if were totally different brick.

The stain I consider the darker patch around 2m high and it seems to be getting a little lighter towards the bottom (color matches the rest of the building there).

Could very well be just some unfortunate choice of placing different colored bricks.

It was built 100 year ago approx.

Please feel free to post it. I believe asking a builder to clean the brick would not hurt even if it would resolve the difference in color.

Perhaps I’ll try to get some brick friendly plants/English ivy.

[Click to enlarge any image]

On 2021-05-08 by (mod)

Ok now, which is the area that you are considering the stain? the darker brick, or the whiter brick?

It looks as if a portion of the wall has been re-built.

Where is this building and what is its age?

What is the history of repairs to the surface of the patio-roof?

On 2021-05-08 by Eva28

It is a roof terrace. I’ll try and get you more pictures. On the indoor on the ground floor is the bathroom but I did not see dampness there. It also was renovated recently.

 

On 2021-05-08 by (mod)

I see

- dark stains just below a wall top coping that looks like a roof parapet wall

- areas where mortar is more-white than others

- areas of more-red brick over a door, probably a repair or reconstruction

- area of redder brick below whiter brick that may also be an area of prior repairs.

I would need some more photo showing more of the building, at a distance so I can get some perspective in context, also what's above, is that a flat roof?

On 2021-05-08 by Eva28

Hi! I can’t figure out why there’s a discoloration on the brick of my house I just bought. [Photo above]

Thanks
Eva

I hope you are keeping well in these strange times! I wonder if you have an idea why the below brick wall is discolored (if helpful, on the inside it’s a recently renovated bathroom). Is there any way to fix it ?

On 2021-04-18 by (mod) - dark red-brown soil stains on white brick, near ground lee3l

@MC,

The most likely cause of the discoloration of brick on your veneer wall close to the ground is rain splash-up, caused, in turn by spillage of water from the roof edge.

The proper solution, if that's the case is to make sure that the gutters are cleaned and properly sloped and draining away from the house and not spilling over into that area.

When you've taken care of that it would make sense to clean the brick surface and if the paint has actually come off of the brick then you'll need to repaint the bricks.

On 2021-04-18 by MC

I have a brick face facade on my home. I believe it has a white wash finish.

There are reddish brown stains on it. When it gets wet, you can literally see a what appears the red brick from underneath. I would like to apply sealer but fearful that the red color of brick will stay permanently on the surface.

Is there anything I can do for remedying the staining and waterproofing it somehow so that there is no discoloration when it gets wet ?

On 2020-09-16 - by (mod) -

Try gentle brushing with vinegar or other household cleaners; rinse thoroughly

On 2020-09-15 by meryl

A hibiscus bush with big red flowers greww nest to a newly painted white brick wall, I tried to remove the dried leaves with a sponse and water and it let i light green stain. How can i remove the stain so the brick will return to white color

On 2020-09-10 - by (mod) -

That is weird, David. Try attaching a sharp photo or several (one per comment)

On 2020-09-10 by David

I have a weird issue on the outer brick wall of my house. It is a clear substance--completely transparent--that looks like very thin melted plastic adhering in irregular patterns, almost like it was dripped and pooled in random patterns. .

At first I thought maybe a small clear piece of plastic had melted on the bricks--but then more of the stuff showed up after the previous spots had started to fade.

I'm pretty sure no one is deliberately doing it in the night. So far my best guess is maybe some kind of pollen or sap is being blown and splattered occasionally on that wall.

Haven't found it on any other wall. I am really perplexed as to what it might be. Any thoughts?

On 2020-08-14 - by (mod) -

Marie

Thank you for the interesting photos and question about mortar deterioration in your brick veneer wall.

I think we have a combination of leaks into the wall

(see those openings in the mortar joints in your photo at top left?)

and perhaps variations in the mortar mix.

Start by finding and sealing leaks into the veneer wall.

On 2020-08-11 by Marie

Why only in a couple of area of our home but both under cover do i have the mortar turning to dust and in some places turning green.

Also a brick is turning white.

Please help, How can I treat this.

On 2020-07-09 - by (mod) -

There are several commercial iron-stain removers such as Iron-Out that may work. Try first in an unobtrusive spot.

On 2020-07-09 by Tim

Iron water stain on brick(boat house). What is the safest chemical and environmentally friendly with plants by the wall?

On 2020-06-14 - by (mod) -

Liz

After cleaning off the soot or creosote,

and having the flue inspected for fire-safety,

be sure the chimney is tall enough - 2 ft. above the ridge or 2 ft above point of contact with roof surface of a horizontal line drawn from chimney top to touch the nearest roof surface;

Ask your chimney sweep if your chimney has the right type of cap - preventing downdrafts;

I'm reluctant to rely on a larger cap since we'll just move the stain from the chimney to the roof surface, so we're left with taking care to burn dry, low-sap wood at sufficient temperature.

On 2020-06-13 by Liz

How can I prevent a black stain on the outside of my house just below the chimney I have a wood burning stove

On 2020-05-18 by Anonymous

Thank you

On 2020-05-18 - by (mod) -

Gabriel

Two approaches to removing the reddish stain on your brick are

1. try some masonry cleaners or iron removers as discussed in the article above

2. check out the list of likely causes of red stains on brick - also in the article above - to see if, by narrowing down the probable cause of the reddish stains in your photo we can home in on the most-effective cleaner

3. inspect the building, rooftop to siding bottom, including interior, plumbing, mechanical systems, to find the leak or defect that is causing this stain to appear in this particular location.

In my view this is an important step as otherwise we don't know that the stain isn't just a telltale of a more-serious hidden problem.

On 2020-05-18 by Gabriel

It seems that my aluminum siding has run into my bricks. Not sure if it’s rust or just the siding color. Hi do I safely take off without compromising the brick color?
Thanks

Hi, it seems that my brown aluminium siding is running down on my bricks. I’m not sure if it’s rust or just the color of the siding. Any suggestions how to take it off without compromising the color of the bricks

...

Continue reading at STONE, STUCCO & BRICK CLEANING METHODS for cleaning approaches useful for brick or stone surfaces, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see STAINS on BRICK SURFACES FAQs - questions and answers posted originally on this page.

Or see these

Recommended Articles

• BRICK FOUNDATIONS & WALLS - home
• BRICK WALL REPAIR METHODS
• CHIMNEY STAINS & LEAKS
• CHIMNEY STAINS, INDOORS
• EFFLORESCENCE SALTS & WHITE DEPOSITS
• GRAFFITI REMOVAL FROM BRICK CONCRETE STONE SURFACES
• MASONRY CLEANERS
• MOLD APPEARANCE - STUFF THAT IS NOT MOLD or other discolouration found on brick surfaces.
• STAIN DIAGNOSIS on BUILDING EXTERIORS - home
• STAINS on BRICK SURFACES
• STAINS on INDOOR SURFACES, PHOTO GUIDE
• STONE, STUCCO & BRICK CLEANING METHODS
• STONE SURFACE CLEANING & ORGANIC GROWTH PREVENTION (Algae, Fungus, Lichens, Moss) from Stone, Brick, or Concrete Surface
• VINES & SHRUBS on BUILDING WALLS, CHIMNEYS

Suggested citation for this web page

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

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING STAINS

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