The shaded parts of the roof were getting moss/lichen collection and that will accelerate deterioration faster than anything. I had consulted some friends in home construction and they advised against the following steps. Don't power wash, don't go up on the roof in the summer [dry shakes crack and add to leaks] and only use Hi pressure air to clean the moss/lichen. They suggested a 3 stage process to help the roof reach it's full life.
- Hi pressure air clean.
- Apply anti-moss formula to the roof shakes [spray on].
- after 6 months re-clean and apply an oil for shakes.
- Repeat in 5-7 years.
I have had a leak over a small roof over the kitchen area in the back but this roof has a very shallow slope and therefore drainage is slower and stay wet in winter.
My advice is don't talk yourself into a new roof unless clear global failure is evident. Get advice from several sources and let them know what your goals are for your roof. If you want it to last you likely will hear feedback that involves maintenance but if you ask "do you think it needs replacement" you will likely only hear about replacement. I think it all depends on what you want to do. Anyone out there able to tell us what a new roof costs these days and who's a good contractor?
-ted
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