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White Mold

Identifying white mold growth in your home

White mold growth, while a common problem in residential homes, does not receive the same attention as black mold.  Primarily this is due to the fears surrounding more well known black molds, such as Stachybotrys.  However, many white molds are still capable of producing negative health effects and should be dealt with promptly.

Can color be used to identify the type of mold?

You cannot positively determine the exact type of mold based on the color.  However, the color can be used to rule out certain types of mold.   For example, Stachybotrys is always black.  If you find white mold growth on a pair of shoes, you can rest assured it is not stachybotrys.  The same is true of chaetomium and a number of other mold types.

Unfortunately, many types of mold such as Cladosporium and Penicillium/Aspergillus come in a variety of colors.  These molds can appear in everything from white or green to brown and black.  This limits our ability to determine the exact type of mold by simply assessing its color.  To fully identify the species or genus of mold a sample must be collected and sent to a lab for analysis.

Common locations for white mold growth

Each type of mold has a preference for certain conditions.  For example, stachybotrys often prefers highly saturated materials, such as sheet rock after a flooding event.  Because of these preferences, white mold growth is often found in the same location.  Below are the most common areas.


Mold growth on furniture is often white in color.  Additionally, the mold typically has a 3 dimensional, fuzzy growth aspect.

White mold growth on dresser

White mold growth on back side of dresser.

Clothing & Textiles

Clothing, shoes, backpacks – when mold attacks contents within the home, it’s often white or light green in color.  This is especially true for leather items.  The good news?  It’s easier to remove white mold than black mold.  While the latter often leaves behind permanent stains, white mold can often be fully removed.

White mold growing on leather sandals.

White mold growth on leather sandals.

Backpack with white mold growth.

Textile, such as backpacks are often attacked by white mold.

Attic sheathing and framing

White mold tends to grow in high humidity environments rather than areas suffering from total saturation.  This is why it’s less common to see mold growth on base trim after a flooding event.  The vast majority of attic mold is caused by humidity, which is why white mold growth is common here.

White mold growth inside an attic

White mold growth inside an attic


White mold is often found in two locations in a crawlspace, exposed soil and the lower portions of the floor joists.  In cool climates, mold growth on floor joists is rare.  But when it occurs, it’s often white in color.

Heavy white mold growing on floor joists.

Heavy white mold growth on floor joists.

In wet climates, exposed soil in a crawlspace will often propagate mold growth.  Typically this is due to a missing or incomplete vapor barrier.  The combination of an organic food source (dirt), excess moisture and limited airflow creates the perfect conditions for mold growth.  In nearly all cases, white rather than black mold grows in the soil.

White mold growing on exposed dirt in the crawlspace.

White mold growing on exposed soil in crawlspace.

How can I tell the difference between white mold and efflorescence?

White mold growth provides an additional challenge because it is often confused with efflorescence, a crystalline growth structure found on concrete and masonry surfaces.  Efflorescence occurs when water moves through a masonry structure, bringing unbounded salts to the surface.  When the water evaporates, a white, fluffy structure is left behind.  This growth, while harmless, can appear very similar to white mold growth.

White mold can be found anywhere conditions conducive to mold growth are present.  Common areas of white mold growth include attic sheathing and crawlspace framing.

A trained mold inspector can readily determine if the growth structure is from white mold or efflorescence.  Additionally, efflorescence will typically dissolve under the application of a water mist, while mold growth will not.  Other helpful distinguishing characteristics include the material of the substrate.  Efflorescence will only occur on concrete, brick or other masonry structures.  If you find a white mold like substance on sheet rock or wood, you can certainly rule out efflorescence.  Another indication, though imperfect, is the presence of a mold smell.  Efflorescence is odorless, while mold growth often produces a musty odor.

Efflorescence on Concrete

Efflorescence on Concrete


Is white mold dangerous?

Many molds can provoke allergic responses in sensitive individuals.  No area of significant mold growth within the home should be considered safe.  Proper identification of the underlying cause, removal and cleanup should be performed regardless of the color of the mold growth.

What tests are used to identify white mold?

Direct mold sampling can be used to identify the species of white mold.  Types of direct sampling include tape lift, swab and bulk samples.  These samples are collected by a technician and sent to a laboratory for analysis.  The lab will first determine if the suspect growth is mold, and if so, what species of mold.

Are there any special concerns for mold remediation when dealing with white mold?

Your approach to mold cleanup should remain the same regardless of the color.  Remember, many types of molds, even non-toxic molds, are capable of causing an allergic response.  Because of this, the color of the mold is inconsequential.  Many non-allergenic molds are white, as are a number of allergenic molds.  Confusing the issue even more is the fact that we simply don’t know the allergenic capabilities of the vast majority of molds.  Conclusion = treat them all the same.

Your Questions – Our Answers

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I'm in a bungalow with 7month old twins. There is mold on every wall, most are black but one wall is whit and it is a fungal type growth on top of the wallpaper, it looks like rounded lumps of cotton wool. It's privately rented' what is it and what should i do?

If mold growth is visible on every wall, you’re likely dealing with a humidity based problem.  This occurs when a home has insufficient ventilation.  If the home has poorly insulated walls, the problem will be more severe.  Due to the severity of the mold growth, I recommend calling a local professional (but watch out for opportunist who overcharge).  In the meantime, I recommend improving your ventilation by running your bathroom exhaust fan 24/7 and cracking a window if possible.  This will reduce condensation throughout the home.  If the bathroom does not have an exhaust fan, install a Panasonic WhisperGreen fan.

Will painting concrete keep efflorescence from coming back?

If the problem is fairly mild, painting the concrete will reduce or greatly slow down the return of the issue.  However, if the problem is substantial, the vapor movement will cause the paint to bubble and peel.  Make sure you use clean and prep the wall and use a paint specially formulated for concrete.  Specialty coatings designed to stop vapor movement do exist, but they typically work best on new concrete.

It’s always best to begin with an investigation of the moisture source.  For example, check the downspouts above to ensure the water is directed away from the concrete wall.

Does bleach kill mold?

Yes, bleach can effectively kill/disable mold on hard surfaces.  See this study.  However, bleach has several negative characteristics (stains materials, unhealthy for humans, etc.)  Therefore, mold remediation professionals often use alternative chemicals such as quaternary ammonium compounds.  Organic, plant based chemicals such as Benefect are effective as well.


How do you clean the white mold off and keep it off? It’s on the bottom of wood doors and trim and cabinets.

It’s critical you first identify the cause of the mold.  Without addressing the underlying moisture source, the mold growth will return.  No chemical can prevent mold growth if elevated moisture is present.  In time, the mold will simply grow on top of the new dust that settles on top of the cleaner/coating.

Assuming the area of mold growth is fairly small, the mold growth can be scrubbed off with a detergent/water solution.   More powerful chemicals, such as bleach or quaternary ammomium compounds are necessary to kill the mold.  However, because you’re physically removing the mold by scrubbing and wiping, the killing power of the cleaner is not necessary.  White mold growth can typically be removed without leaving lingering staining.  If staining is visible after scrubbing, you’ll have to sand and refinish the material to address the discoloration.