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What is Indoor Mould and What Causes It?

Updated on
April 17, 2024

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What is Mould?

Mould is a fungus that can grow indoors if the conditions are right. Mould likes darkness, and feeds on feeds on moisture (damp or condensation) and cellulose (found in most building materials). When mould is visible to the human eye, it's typically a mould colony that you're seeing. In other words, it's a mould factory formed of vast numbers of mould spores. A mould colony produces spores that are transported through the air or by becoming attached to clothing, belongings, human skin or animal fur. They can also be inhaled or absorbed through skin. Once a mould spore finds a new home it can germinate and form a new mould colony. Mould is often identified as black spots or patches on walls or ceilings, often associated with a musty smell. The reality is that mould can take many forms, be it shape or colour. Colour doesn't indicate species either, often the colour of mould is a result of the food available to it. If you suspect that mould is present in your home or building, it's important to take action and remove it. Indoor mould can be tough to remove, so it is important to get professional help.

Types of Indoor Mould

As eluded to in the previous section, mould can take many forms. It can be black, white, red, green and anything and everything in between. It can appear fluffy and dry or sludgy and wet. A lot depends on the conditions in which it has taken root. Twelve common indoor mould strains include; Acremonium, Alternaria, Aspergillus, Aureobasidium, Chaetomium, Cladosporium, Fusarium, Mucor, Penicillium, Stachybotrys, Trichoderma and Ulocladium. Each strain produces their own array of mycotoxins which can cause a range of adverse health effects. If you're interested in learning more about mould strains, feel free to peruse this article.

What Causes Mould?

Mould is an extremely common problem that can affect any home. It can come from a leaky roof, flood, or any form of structural damage. In the vast majority of cases however, it is caused by condensation - often caused by a mix of everyday activities and poor ventilation. Let's take a look at some of the most common causes of indoor mould growth:


Mould is a fungus that thrives in moist environments, your home is no exception. High humidity levels are caused by everyday activities like cooking, showering and drying clothes to name a few. Making sure to keep your home dry and clean will help keep humidity levels down and ventilation plays a key role. Opening windows, using extractor fans and dehumidifiers are extremely effective in this regard.


Mould growth is always a concern, especially in damp and humid environments. Condensation, which is water vapour turned into liquid, is the result of humidity. The most common cause of mould growth is condensation - which occurs when water droplets from the humidity in the air combine with oxygen. If you already practice humidity reducing behaviours, i.e. good ventilation, and you're still seeing damp surfaces in your home or building, reach out to a mould removal company like ourselves. We don't just remove mould, we also conduct surveys which help identify the cause of excess moisture.

Structural Damp

If you notice any signs of mould growth, it's important to take action right away. This includes dealing with the source of moisture or dampness, as well as improving ventilation and air circulation. Mould can cause a lot of problems such as allergic reactions and asthma attacks. As mentioned above, if you ventilate your property well and still experience excess dampness and moisture in your property, there's a good chance you may have structural issues that need addressing. Some mould remediation specialists, ourselves included, will help you identify the source of any water ingress and, by extension, the likely source of any mould growth.

Poor Ventilation

Proper ventilation is one of the most important factors in controlling moisture and mould growth. If your home doesn't have proper ventilation, humidity levels will be high and condensation will occur, which can lead to mould growth which opens up a host of possible dangers including health problems and structural damage. Condensation (often caused by poor ventilation is the Number One Cause of Indoor Mold Growth: Poor ventilation is by far the biggest cause of indoor mould growth - 75%! In other words, if you want to keep your home free from mould, make sure that adequate ventilation is ensured at all times.

How to Prevent Mould From Occurring

Finding mould growth in your home can be stressful and frightening given the possible adverse health outcomes and structural damage. Outside of the causes listed above, mould can also grow on dry surfaces like wallpaper or wood. This means that even if you don't see any visible signs of mould, it might still be present and growing. It's important to know what causes it, so you can take preventative measures to stop it from occurring. Below are some simple ways to reduce the environmental factors that can cause mould growth:

Reduce Moisture

There are various ways to reduce air moisture levels in order to prevent mould from growing. One of the most common methods is by using a dehumidifier. By removing excess moisture, this helps stop mould growth. There are other measures that can also be taken, such as airing out your home on a regular basis and using air purifiers. All of these steps will help keep your home healthy and free from mould!


It's important to keep your home clean and free of dust, dirt, and other debris. This will help to prevent mould problems in the house as one source upon which mould feeds is something broadly termed '. In addition to regular cleaning, it may also be necessary to use a dehumidifier if the humidity levels are high. And make sure you follow the mold prevention guidelines below so that you don't have any issues with this pesky fungi in the first place: - Keep food storage areas clean - storing food near damp surfaces can lead to bacteria growth leading to spoilage; - Use proper ventilation - Make sure windows and doors are open during dry spells for fresh air circulation; - Avoid using bleach or ammonia products on carpets or furniture because they can damage them; - Clean all surfaces regularly - Mold loves damp, dark environments so make sure everything is cleaned at least once a week including ceilings, walls & flooring.

Ventilation Helps Prevent Mould

Mould is a dangerous fungus that can quickly form in damp and humid environments. If you find mould growing on any surfaces in your home, it's important to call a professional as soon as possible. Good ventilation is one of the key factors that helps prevent mould from growing. Make sure all windows and doors are open at all times to allow fresh air into the building, and clean up any spills or messes immediately so they don't cause moisture build-up. In addition, always keep your home clean by regularly cleaning areas where mould may be present with mold-free cleaners.

Dispose of Mouldy Belongings

Mould is a fungus that can cause serious health problems if it grows unchecked in your home. To keep mould from forming and spreading, make sure to maintain good air ventilation and clean up any spills as soon as they occur. If you notice any signs of mould, don't hesitate to contact a professional - they can help you take steps to prevent its spread. When it comes to mould, organic materials like hair and dander are especially prone to growth. This is because dampness and darkness provide the perfect conditions for the fungus to grow rapidly. So if you live in an area with high humidity or poor air quality, make sure not only do you take preventive measures against mold; but also take care of your personal hygiene by wearing gloves when washing hands or clothes in direct sunlight.

Make Sure Your Home Doesn't Let Moisture In

Mould is a common problem in damp environments, and can cause a lot of discomfort for people living in them. If you notice any mould growing on surfaces or walls, it's important to take action as soon as possible. To clean up the area and prevent moisture from entering again: seal off the moisture source with bricks, tiles, or plastic sheeting; clean up the mess created; and replace damaged materials. If signs of mould are present: remove all contaminated items including carpets, wallpaper, insulation etc.; pump out waterlogged areas using a dehumidifier; install airtight doors and windows (or double-wall PVC pipes); use mold inhibitors if needed; hire professionals to conduct further restoration work if necessary.

Keep Your Home Insulated

There is a lot of talk these days about mould and its potential health risks. It's important to be aware of the reasons why mould can grow, as well as the various steps you can take to prevent it from happening in your home. For starters, moisture accumulates due to many causes like excess humidity, poor ventilation, dirty surfaces etcetera. This built-up moisture creates ideal conditions for mold growth. To combat this problem, seal cracks and gaps in the building envelope; use dehumidifiers or air purifiers; install ventilation systems if needed; and insulate your home properly with R-19 insulation (or higher). If you experience any signs that your home has become too humid or dry - itchy eyes, asthma symptoms etc.- then it's probably time to act on behalf of both your safety and wellbeing by seeking professional help. A damp environment only promotes fungi growth so leaving everything as is might not be such a good idea after all.

How does it affect your health?

Mold is a fungus that grows in damp environments, such as homes and offices. It can cause a variety of health problems, such as allergic reactions and asthma attacks. If you experience any of these symptoms, it's important to get tested for mold. In addition, mold can lead to more serious illnesses like bronchitis and pneumonia. To protect yourself and your family, it's important to follow a few simple steps every week to reduce the amount of mold in your home. Start by cleaning it every week to rid it of any dirt, dust, or debris that may be harboring mold. Also, be sure to keep your home free of excess moisture - this can be done by installing air conditioning, using dehumidifiers, or using rainwater harvesting. And last but not least, if you notice any mold growth, take action right away.


Mold is a common indoor fungus that can cause health problems in people of all ages. It starts as a tiny fungus and can grow rapidly, invading any dry and damp areas of your home. Even small amounts of mould can cause serious health problems, including asthma, allergies, and respiratory problems. If you are concerned about your health and the health of your family, make sure to get tested for mould and take appropriate steps to prevent its growth. Thanks for reading.