The answer to 'underlayment water stains' is that they are a common issue that can have several potential causes, including roof leaks, improper installation, or damage to the underlayment itself. Water stains on the underlayment can indicate a more serious problem that needs to be addressed.
Some common causes of underlayment water stains include roof leaks, condensation, or poor ventilation in the attic. The underlayment is the layer installed between the roof deck and the shingles, and it plays a crucial role in protecting the roof from water damage. If the underlayment becomes saturated with water, it can lead to mold, rot, and other structural issues.