The answer to 'why is my underlayment missing shingles' is that the underlayment is likely damaged or improperly installed. This can happen due to factors like severe weather, poor workmanship during the original roof installation, or simply normal wear and tear over time. When the underlayment is missing or damaged, it leaves the roof decking exposed and vulnerable to leaks and further damage.
Some common symptoms include visible gaps or holes in the underlayment, shingles that are curling or lifting up, and water stains or leaks inside the home. Addressing this issue promptly is important to prevent more extensive and costly roof repairs down the line.