Are some of your exterior wood elements being attacked by wood destroying insects?  This is common in the Pacific Northwest, but doesn’t mean you should ignore it.  Insects such as anobiid beetles can work away at damaging the structural integrity of your home leaving exit holes and underlying damage in their wake.   It’s all about moisture; elevated moisture attracts wood destroying insects leading to structural damage of building components.  Keeping exterior elements properly sealed and dry will go a long way towards preventing wood destroying insects from damaging your home.