The answer to 'underlayment sagging' is that underlayment sagging is a common roofing issue caused by improper installation, moisture damage, or aging materials. Symptoms include visible sagging or dips in the roof surface, which can lead to leaks and other problems. To fix sagging underlayment, the solution typically involves removing and replacing the damaged sections.
In many cases, underlayment sagging is a job best left to professional roofers. Attempting DIY repairs can be risky and may result in further damage if not done correctly. Homeowners should consult a qualified roofing contractor to properly assess the issue and make the necessary repairs.