On Sun, 5 Aug 2018 14:56:50 -0700 (PDT), wrote:

On Sunday, August 5, 2018 at 4:25:24 PM UTC-5, Davej wrote:
In a 20 year old house how common is it to find windows
were not properly flashed? The Tyvek is simply cut out
around the windows. It isn't even taped to the window
frames.

Sounds like a DIY person did not know what they were doing.

I'd be surprised if there isn't some structure damage from rain or
even high power bills from leaking windows.