So I have an ongoing leak that we're having trouble figuring out. Here's the deal... The dormer walls on the second floor of my house meet up with a roof at the bottom. The walls of the dormer are wood shake. We can go a few months with some pretty hard rain and no leaks in the pitched ceiling that the dormer meets, but then all of a sudden, it leaks randomly during a heavy rain storm. I went on the roof, sprayed the hose and was able to recreate the leak, however, all gaps seem to be secured and I can't see any visible gaps for water to leak in. In addition, I noticed a lot of the wood shake along the bottom half of the dormer seem soft and easily torn when wet and brittle when dry. Also there is no visible flashing where the roof and dormer meet. Is it possible the shake is soaking up water when soaked really good and seeping the water down the wall behind them?

Can anyone offer any thoughts?