The answer to 'why is my flashing water stains' is that there are several common causes, including improper installation, damage, or deterioration of the flashing. Flashing is the thin metal or plastic material used to create a waterproof seal around roof features like chimneys, vents, and skylights. If the flashing is not installed correctly or becomes damaged over time, it can allow water to seep through and cause staining on the interior or exterior of your home.
Some common symptoms of flashing issues include visible water stains, mold or mildew growth, and leaks around the affected areas. To fix the problem, you may need to re-seal or replace the flashing, which is usually a job best left to a professional roofing contractor. Attempting to repair flashing without the proper skills and tools can lead to further damage, so it's generally advisable to call in an expert unless you have extensive roofing experience.