Got Mold?

Mold spores are like tiny seeds, and they are floating in the air all around us. They stick to most surfaces in our homes. When you add moisture to these areas, it can allow the growth process to start. Think of a seed in the dirt . . . the seed can remain in dirt for a period of time doing nothing until water is introduced. If these surfaces remain dry and within good ventilation, the tiny spores can remain on these surfaces for an extended period of time with little to no issue.



The most common places that I find mold in homes when I am performing a home inspection are attics, bathrooms and basements. The presence of mold in an attic is often caused by one or more of the following issues: 1) unsealed openings such as where wiring, plumbing or ductwork enter the attic or at the attic access location between the attic and living space, 2) a roof leak that was left unrepaired for a period of time, 3) inadequate roof/attic ventilation, 4) bathroom exhaust fans discharging into the attic, or 5) inadequate attic insulation, including the attic access panel or door.

All ventilation systems should terminate to the home’s exterior. If a bathroom or kitchen ventilation fan discharges into the attic, even just above the soffit venting, the warm, moist air from these conditioned spaces tends to condensate on the underside of the cooler side of the roof that faces away from the sun. This portion of the roof generally stays cool longer each morning and these cold surfaces will allow for condensation just like a cold bathroom mirror during a hot shower. In most cases, it is easy to reroute bathroom or kitchen exhaust fans beyond the home’s soffit or through gable end siding. If the vent tubing runs above attic insulation, an insulation sock should be installed on the exposed vent tubing to prevent condensation within the tubing in the winter. Otherwise, condensation can run back down the tubing and drip back into a bathroom through the fan for example.

A properly vented attic will allow the warm and moist air from the living space to exit to the exterior through the ridge venting and not within the attic, as well as help preserve the life of many roof types and lower the amount of energy needed to heat and cool the home.

During my home inspections, I always recommend that the client periodically checks around all accessible plumbing to look for small leaks. A small leak is often easier and inexpensive to repair and will most often cause less damage to occur than a full-blown burst pipe. A small leak undetected may lead to mold growth and/or insect infestation.

Mold growth in basements is most often related to exterior drainage and grading. Downspouts should drain at least four feet from the home’s foundation, and the exterior grading should encourage drainage away from the home. Having your inspector also perform an infrared inspection of a finished basement is recommended since even if no mold is visible in the accessible areas, this extra inspection could indicate if there is unforeseen recent or active water infiltration occurring behind those fixed surfaces that could potentially lead to mold in the future.

So what if you see mold?

Don’t panic. A qualified and properly trained mold professional can perform mold testing. The person performing the mold testing should have mold-specific errors and omissions insurance (E&O). Basic home inspector E&O insurance alone specifically excludes mold.



Mold testing generally consists of one or both types of sampling techniques. A swab test will determine what type (or types) of mold exists specifically on the surface where mold, or suspected mold, is visually seen. This is often on a wall or ceiling. Air sampling will entail measured amounts of air being pulled into a special plastic testing cartridge and will give a general idea as to what type(s) of mold(s) exit in the tested area/room as well as the spore count(s). If no visible mold exists, air sampling will probably be the only test able to be performed. When air testing is performed, an exterior reference sample is required so that the lab analyzing the samples has something to compare the interior air samples to. Since there is no set standard as to most mold types and spore counts, the exterior sample sets the ‘standard’ to allow comparison with the interior air sample(s).

As an example, an exterior air sample shows 150 spores per cubic liter of air of type A, 50 spores per cubic liter of air of type B and 0 spores of mold type C. Interior air samples show 180 spores per cubic liter of air of type A, 1,500 spores per cubic liter of air of type B and 2,000 spores per cubic liter of air of type C. The analysis would indicate that the sources of mold type B and C are within/inside the home. There is no recognized standard regarding what is safe for mold spore counts, assuming none are the types considered to be toxic. Since mold counts and types vary depending upon where you are located and what time of year it is, the comparison between indoor and outdoor samples is used. Of course any spore count of a toxic mold type in the home would be an issue.

Mold types are commonly broken down into three types: allergen, pathogen and toxic. An allergen is the most common type and may affect certain people who have sensitivities to specific molds. Pathogenic molds are ones that most often affect people with an immune-deficiency such as those who have certain illnesses. Toxic molds are the most severe and will most likely affect anyone who comes in contact with it.

Someone who has no known allergies can actually acquire an allergy to a type(s) of mold simply from exposure to it over time. You could have 10 people in a room with a certain type of mold and possibly only one or two people who have an allergy to that type may show symptoms whereas the rest of the people may show no symptoms. If a toxic mold type exists in that room, chances are good that just about all 10 people would show some adverse reaction or symptoms over a period of time.

After the testing is performed, the mold tester sends the testing samples to a certified lab for analysis. Once the lab report is received, the next step is most often to consult a qualified indoor air quality specialist, industrial hygienist or a qualified mold remediation professional should the lab report indicate high interior spore counts. Some local companies who specialize in cleanup after fire or flood may also be qualified for mold remediation. Of course also addressing the source of the water moisture or lack of ventilation must always be part of any mold remediation process and should be performed as soon as the problem is determined to help minimize the damage.

Keep in mind that mold detection and mold testing is considered well outside the scope of the American Society of Home Inspectors Standard of Practice. In other words, mold is not part of a home inspection. If a home inspector sees visual evidence of mold during an inspection, he should note this in his inspection report and recommend evaluation and/or removal of the mold and any affected building materials such as drywall, trim, carpet, insulation, etc. by a qualified mold professional.

Don’t ‘bleach it away’!

Many people assume that bleach is the be-all-end-all of mold cleanup, but this simply is not true. Some mold spore types may be eradicated using bleach; but many types may come right back, and others will not be affected at all by bleach. Bleach may simply mask a mold problem for a short period of time, and the mold problem may get considerably worse.

Some mold types need to be professionally treated to ensure that the spores can’t grow back again or are fully removed. I’ve seen some homeowners spray chlorine bleach on ceiling mold and appear to remove the mold only to see the mold come back a few days later. If mold is observed growing on bathtub caulking, it very well may be able to be cleaned with certain bathroom cleaning products or even by simply removing the caulking. If visible mold growth covers 10 square feet, professional remediation is often needed to properly address the mold problem. An improper treatment may actually encourage further growth into a larger mold problem.

Mold growth on certain household surfaces may be able to be removed. An example would be surface mold on wood studs that could be sanded. Other surfaces like drywall need to be completely removed once they get wet and moldy since the cellulose that exists in paper is the very food that mold needs to grow and thrive. If mold grows on books or drywall, these materials need to be carefully removed from the home to help ensure the mold spores don’t get disturbed and released into the home’s air. When building a new home, for example, rain water often gets into the partially constructed home before it is fully closed up by siding, roofing, windows, etc. The home should be allowed to fully dry before any insulation, drywall, flooring, etc. are installed.

You can’t typically determine the type of mold simply by its color. Mold types come in all different colors from black and yellow to green and brown to orange. If you see what appears to be mold growth in the home, that is a sign that something needs to be done promptly . . . time to call in a professional. A delay could put the home’s inhabitants in jeopardy for health problems and possibly lead to the home not being able to be occupied.

Matthew Steger, ACI, WIN Home Inspection 

Facts, opinions and information expressed in the Closing Comments Blog represent the work of the author and are believed to be accurate, but are not guaranteed. The Lancaster County Association of Realtors® is not liable for any potential errors, omissions or outdated information. If errors are noted within a post, please notify the Association. Posts represent the author’s opinion and are not necessarily the opinion of the Association.