Oregon State University did a study explaining how moss can damage your roof and when it is time to take action. Studies have also shown the effects on a roof over a long period of time in a controlled setting and based off experience based data moss can remove 5-15 years in the PNW region. Depending on the size of your house you could be looking anywhere from $15,000-$25,000 for a roof replacement due to grainule loss and water damage that moss brings take action early and give us a call to receive a free quote