Causes of Mold in Homes
What Mold Needs to Grow
To grow in your home mold needs the following things:
- Moisture or humidity
- A food source
- Mold spores present in the air
- Darkness
- Warmth
- Oxygen
- Time
How Mold Grows
Molds reproduce by spreading microscopic spores through the air. Once mold spores land on a damp surface they can begin to grow and digest the substance they are growing on.
Nearly any organic material is suitable for mold growth as long as there is a build up of moisture. Most molds only need the surface to be damp for 24-48 hours before they can start to grow.
Therefore all mold problems in the home involve moisture problems as the cause.
Humidity Causes Mold
Mold only needs the humidity level in your home to be higher than 55% in order to grow.
If you live in an area of high humidity such as on the coast or near a large body of water then the humidity in the natural air can cause mold growth in your home.
Also when moisture from other water sources in your home (such as drying wet clothes) evaporates into the air it raises the humidity inside even higher than the air outside. If your home has poor ventilation then the humidity will often remain high for a long time.
Using your home's HVAC system's climate control can also make the humidity vary inside greatly compared with outside as it artificially heats or cools your house.
Some people also use humidifiers in their homes. If you need to use a humidifier in your home you should make sure to keep the humidity below 55% to avoid mold growth.
Besides feeding mold a high humidity level also means standing water and damp surfaces and materials take longer to dry out which can exacerbate the problem.
Leaking Pipes Cause Mold
Water leaks from pipes are a common cause of mold growth. Often the leak can be in a place out of view and can go undetected for a long period of time. By the time the leak has been discovered mold will probably have already begun to grow, especially if the leak is in a place hard to find such as within a wall cavity.
Leaks in Roof and Walls Cause Mold
As with leaking pipes, a leaking roof may not be discovered until it has already caused mold to grow. You should check the attic for any water intrusions caused by the roof leaking and also look at the ceiling for water damage or for any mold growth.
Blocked gutters can create a build up of water which may also seep into your home through the walls or ceiling. Cracks in walls might also let outside water leak into the house.
Condensation Causes Mold
Cold surfaces in the home can create condensation. Condensation collects on cold metal pipes as well as on cold concrete floors, even if there is carpet over the top, and on walls. Places like this where condensation occurs are prime spots for mold growth.
Poor Ventilation Causes Mold
If your home is poorly ventilated it can create pockets of stagnant moist air which mold thrives in. Steam and water which evaporate into the air create humidity inside which then needs to be circulated outdoors through windows to keep the moisture level balanced.
Poor ventilation will also mean wet surfaces dry out more slowly. Ventilation is especially important in rooms such as the bathroom and the kitchen where there is a lot of steam.
Wet Clothes Cause Mold
If you leave clothes wet for a long period of time in your house mold can grow on them as well as on other surfaces because of the moisture the clothes release into your home.
Damp clothes left in a pile waiting to be washed for more than a day can lead to mold growth. Clothes left wet for over a day after being washed may also end up fostering mold.
Clothes dried in a dryer instead of outside on the line release a large amount of moisture into your home if the drier is not vented to outside the house. Drying your clothes inside on indoor clothes lines or racks also releases moisture inside unless the room is well ventilated.
Flooding Causes Mold
It is almost inevitable that some mold problems will develop after your home has been affected by flooding. Obviouly your house will be very wet for a long time during a flood, taking days or even weeks to dry out. Since mold only needs a suitable surface to be wet for 24 hours before it can grow there is a huge risk of mold growth.
Some dangerous toxic molds require more extreme conditions than common molds do, such as the toxic mold Stachybotrys chartarum which requires material to be very wet for several days to grow. A flood can create these conditions putting your home more at risk of being infested with dangerous toxic molds.
Damp Basement Causes Mold
Basements often have higher moisture or humidity because they are usually not well ventilated. They are also often colder and more condensation occurs in colder temperatures which leads to dampness and humidity.
Also any water from leaks in your home will often end up running down to the basement because it is below all the other rooms in the house. Not only is mold likely to grow in these rooms but because they are usually neglected mold growth may not be discovered until it is well set in.
Water at the House's Foundation Causes Mold
Water building up in the yard and ground around the base of your house can cause frequent water problems for the foundation of your home. If the ground around your home slopes towards your house rainwater will end up building up at the foundation.
If this causes constant problems you might even need to do some landscaping to modify the slope of the ground around your home so water drains away from the house. Alternatively ditches and drains can be dug to channel water away from the home.