The answer to 'why is my underlayment' is that the underlayment, which is the protective layer installed beneath the roof shingles, may be damaged or improperly installed. Common causes include water damage, improper installation, or deterioration over time. Symptoms may include visible cracks, tears, or areas where the underlayment is lifting or coming loose.
In many cases, the underlayment can be repaired or replaced as a DIY project, but it's important to properly identify and address the root cause. However, if the damage is extensive or the underlayment was improperly installed during the original roofing, it's best to consult a professional roofing contractor who can properly assess the situation and recommend the appropriate solution.