The answer to 'why is my tile mildew' is that tile mildew is typically caused by excess moisture, poor ventilation, or lack of proper cleaning and maintenance. Tile mildew can appear as black, green, or gray spots or discoloration on the tile surface or grout. It's a common problem in bathrooms, kitchens, and other high-moisture areas.
Some common causes of tile mildew include inadequate ventilation, leaks, high humidity, and not cleaning the tile and grout thoroughly and regularly. Mildew thrives in damp environments, so it's important to address the moisture source and improve air circulation to prevent and remove tile mildew.