What can mold look like inside a house?

Nov 15, 2018

When people think of mold inside their house, they typically think of a big black splotch on the wall or ceiling.  More times than not, this would be correct. But mold has tens of thousands of species and can have a wide variety of colors and show up in different areas for different reasons.  Although the species may look different, they often act the same way; beginning with little dots that are usually circular in shape that grow and get larger when they have ample moisture and nutrients.

Mold from a plumbing leak

Mold on Wall

Photo #1 – Mold on the wall

Moisture Meter


 Photo #2 Moisture meter shows dampness

If you think that this is mold in the pictures above (See Photos #1 and #2), you are correct.  Not only is it mold, but multiple species of mold. You can tell immediately because of the different colors.  In these pictures, mold grew in a washroom when a pipe burst behind the wall. Water, more than any other factor, is the single greatest cause of mold growth.  Obviously, this mold would require extensive remediation, but before any remediation, the source of the moisture (i.e. the burst pipes) needs to be repaired https://www.epa.gov/mold/brief-guide-mold-moisture-and-your-home .

Mold in a basement

Mold in Basement

 Photo #3 – Mold growth on a basement wall

Mold Stains

 Photo #4 – Another example of mold stains

When there is mold in a basement, it usually occurs from a flood or from seepage through a basement wall.  In these pictures (See Photos #3 and #4), mold developed near the basement floor and grew in those areas where the wall was sufficiently damp.   Damp materials can be found several feet away from the liquid water. This is a process called “wicking” and can be seen by taking a paper towel and dipping it into a bowl of water.  In the instances above, the mold is occurring both on the inside and outside of the walls and it became necessary to cut the drywall out to ensure the proper removal of the growth.

After a flooding event occurs in a home, it is very important to dry the area as quickly as possible.  By drying an area within 24 to 48 hours of the flooding, you can interrupt the life cycle of the mold and prevent it from growing https://www.epa.gov/sites/production/files/2015-09/documents/floods.pdf .

Bathroom Mold

Bathroom Mold

 Photo #5 – Mold on a bathroom ceiling

This photo (See Photo #5) shows slightly discolored spots growing on a ceiling directly above a bathroom shower.  Bathrooms can provide the two important factors in promoting mold growth: moisture and nutrients. In this case, the big culprit is elevated humidity (a form of moisture) caused by not providing adequate exhaust and ventilation.  

Often times when we test this, we find that this is Cladosporium mold.  Cladosporium is sometimes referred to as a bathroom mold; it is a common “outdoor mold” and if seen right away can oftentimes be wiped away with a damp cloth.  Unfortunately, if the growth has been there for a long enough period of time and has grown into the wall, the only way to get rid of it is to remove the drywall.

Mold in the attic

Mold in Attic

Photo #6 – Mold on attic sheathing

bathroom duct

Photo #7 – Improper connection of bathroom duct

What can mold in the attic look like?  Sometimes it can look like spots on the sheathing (See Photo #6).  This mold is in the beginning stages of growth, but if left unchecked the mold can grow into large colonies.  Condensation from an improperly connected bathroom exhaust duct (See Photo #7) can provide the moisture for the mold to flourish.  In this situation, you might see dark stains surrounding the roofing nails which may appear to be heavily rusted. Sometimes the stain is nothing more than iron deposits forming around the nail, but it is possible that it is mold growth.  The only way to be sure is to have it tested by a professional with a surface sample.

Mold in Roof

 Photo #8 – Mold due to a roof leak

The mold in the Photo #8 was due to a roof leak.  At this point, the roof needs to be repaired to prevent further moisture.  It should be noted that there are several ways to remove attic mold. We typically recommend roughing the stain with wire brushes, sandpaper, or media blasting as opposed to the common practice of only spraying it with a chemical and painting over it with an antimicrobial paint.      

Mold on furniture, clothing, boxes, etc…

Mold on Chair

 Photo #9 – Mold on a wooden chair

In Photo #9, the mold growing on this wooden chair has the appearance of a white powder.  Mold doesn’t necessarily have to be a dark stain and, as mentioned above, can be seen in a wide variety of colors.  It can show up on boxes, books, papers, paintings or anything else that was derived from a plant or animal. It’s also possible for mold to show up on clothes and shoes.  If it’s on leather, often times it needs to be thrown away. If mold is on a paper-based product or a porous fabric, unfortunately, it probably needs to be thrown away as well.

The final word

Mold spores are everywhere, but if there are moisture and nutrients, mold can grow anywhere. The important thing to realize is that you can not determine with 100% certainty if you have mold unless you test it.  What looks like dirt can, in reality, be mold. If mold is a serious concern due to health issues, be sure to have a professional test it and determine the underlying causes so you can take the necessary steps to eliminate this indoor air quality hazard.