That's a great question! Mould on buildings is a common problem, and it all comes down to water. ​ ​1. How Mould Gets Started (The Foundation Problem) ​Mould spores (tiny "seeds" of mould) are always floating around in the air. They only need three things to start growing: ​ Spores ​Food (anything organic, like wood, drywall, paper, or even dirt) ​Water/Moisture ​ The foundation is often the first place the moisture enters: ​ Wet Earth: When the ground around your home is soaked (from rain, poor drainage, etc.), the water pushes against the concrete foundation. ​Cracks and Leaks: If the foundation has tiny cracks, the water will be forced through them and into your basement or crawlspace. ​Concrete Wicks Water (Like a Sponge): Concrete isn't perfectly solid. ​Bad Drainage: If your yard slopes towards the house or your gutters dump water right next to the foundation, you are constantly feeding water to the walls. ​This foundation moisture raises the humidity. When the humid air touches a cold surface, it creates condensation (water droplets), which is the perfect signal for mould to start growing on your walls, wood, or carpets. ​2. The Remedy: Stopping the Water at the Source ​The only way to get rid of mould for good is to find and stop the source of the moisture. ​Step A: The Outside Fixes (Foundation Protection) ​Make sure the ground around your house slopes away from the foundation. You should never see water pooling near the walls. ​Clear the Gutters: Clean out your gutters and make sure the downspouts (the pipes coming down the house) send water at least 1.5 to 3 m away from the foundation. If you see cracks in the foundation walls, have them professionally sealed to stop water from coming through. ​If you have a dirt crawlspace, cover the entire ground with a thick plastic sheet. This blocks ground moisture from evaporating and making the air damp. ​Use Fans/Ventilation: Run your bathroom and kitchen exhaust fans every time you cook or shower. If your basement is damp, open windows when the outside air is drier. ​If you have water pipes or walls that are very cold and constantly "sweating", insulate them to keep the warm air from touching the cold surface. ​Step C: The Mould Cleanup For small patches, scrub the area with detergent and water. Crucially, ensure the area dries completely within 24 to 48 hours. ​If the mould mould covers a large area, you need to call a professional mould remediation company. They will safely remove the mouldy materials (like drywall or carpet) and clean the remaining structure. Do not just paint over mould—it will come back.