You might notice a strong, musty smell or see black spots on walls or surfaces. Mold can grow behind wallpaper and appear as gray-brown, gray-green, white spots, or thread-like strands. If mold begins to grow in your home or business, it can cause several health issues, like allergies and respiratory problems. If you're experiencing any of these symptoms, you may have mold in your property. If you've had long-term moisture issues in your structure, you most likely have mold growing inside it. Any surface abnormalities like peeling, cracking, warping, bubbling, bowing, or bulging could be signs of water damage somewhere in your property, and that mold has started to grow.