I was told the installers would flash the new door system, but I guess threshold waterproofing wasn't part of the thought process. Not a huge issue, but yet another thing *I* need to address. The old threshold piece can be modified to fit and I'll coat this area with some Henry's before bonding the modified threshold and then caulking it all with black silicone. I'll run a piece of siding across the face of this before installing the threshold cover.