I am asked all the time “How long will my cedar shake roof last?” Here in the Seattle area, there are miles of neighborhoods built with cedar shake roofs. This is particularly true in Redmond, Sammamish and Issaquah on Seattle’s Eastside.
You can expect an original cedar roof to last 17-25 years. The reason I specify “original” roof is because home builders don’t use a premium grade, pressure-treated, 3/4″ cedar shake. If they did, then your roof would last 25-35 years.
whether or not your cedar roof lasts 17 years or 25 years will depend mostly on how steep your roof is. The steeper, the longer it lasts because the water runs off much quicker and the sun doesn’t beat down on it at a direct angle. The sun does the most damage to a cedar shake roof for sure as the South facing side is always worse off then any other side. Having your roof shaded in the afternoon and having a pitch of 8/12 or greater will go a long way in how long your roof lasts.
You can have your shake roof pressure washed and treated but I wouldn’t recommend doing this after it’s 18 years old as it can definitely do more damage than good. We get a lot of calls from those who just had their old shake roof pressure washed. Having the roof treated without being pressure washed is the best bet and even then you really should just stop with any type of maintenance after it gets towards 20 years of age.
Sure there are many companies who will take your money in exchange for “prolonging the life of your cedar roof” but most often it shortens the life. Bottom line: When your cedar shake roof gets 18 years plus in life, don’t hire anyone to maintain it. Just save your money for a new roof.