What Causes Mold in a House?


Mold is a toxic, smelly fungus that can lower the value of a house and sicken those exposed to it. Mold can be found in any moist area and grows on floors, walls and ceilings. The National Association of Homebuilders says mould is most likely to grow in the bathroom, basement or kitchen.

But no area in the house is immune to mould infestation. Therefore, mould must be dealt with quickly to prevent it from spreading.


Moisture is the key factor in mould growth. Millions of mould spores are always in the air. They sometimes attach themselves to a surface and form a colony if environmental conditions are right. The colony is commonly known as mould. Unventilated areas of a house with moisture and stale air are breeding grounds for mould. Mold can form in cold temperatures, which is why it can be found in refrigerators. But it prefers temperatures between 4.44 to 37.7 degrees C.

Health Concerns

Mold fumes are harmful to breathe and exposure can cause allergies and asthma. That is especially true for people susceptible to those ailments. Mold produces organisms called mycotoxins which can also cause irritation of the eyes, skin, nose throat and lungs. The symptoms can be immediate or appear later. The EPA reports that symptoms beyond these are not likely. Research is ongoing to determine if mould exposure causes other health problems.

Property Value

While mould may not always totally destroy a home's value, it can affect it. A house with a mould problem will probably not sell as quickly or for as much as one without mould. Some real estate agents have said mould could cause a 10-percent drop in the price of a house, according to the Wall Street Journal. Since mould can be removed, it's best to get rid of it before putting the house up for sale.

Removing Mold

The Environmental Protection Agency recommends scrubbing a mouldy surface with detergent and water, then drying it thoroughly. Scrub until there are no more visible signs of the mould. Absorbent materials like ceiling tiles or carpet may have to be thrown away if they are too mouldy. Be sure not to paint over mouldy surfaces because the paint may peel away. Always wear gloves, goggles and a respirator when removing mould.

Preventing Mold

There is no way to prevent the amount of mould spores in the house. But it is possible to control the amount of moisture and lessen the chance of the spores forming colonies. Fix any water leaks and dry water-damaged areas within 24 to 48 hours. Keep the humidity level in the house between 30 and 50 per cent. It is also important to keep gutters clean to prevent water from entering through the roof.