On Sun, 16 Feb 2014 13:00:00 -0800 (PST), Greg Rodenhiser
wrote:

The door swings in and the threshold is plastic. I've taken a few more pictures:

https://plus.google.com/u/0/photos/1...99290487074449

This shows the install from inside and outside. Should I be able to see the rail like that from the outside? I have the exact same door on my walk out basement, its also on the same side of the house. It has the same symptoms. Since the basement is unfinished I'm able to get a pretty good view between the door frame and house frame. Everything is dry and see no evidence water ever got in. I can also look under the door threshold of the door in the pictures (from the basement, no sign of water getting down there either).

My thoughts a

1. door needs better stripping at the bottom
2. bad design rip out and replace
3. get a storm door and hope that eliminates the issue

I'm not sure what you are calling the "rail". Is it ribbed plastic of
the wood piece under the door? Cold can make the plastic flex.

It was mentioned by another, about the separation of the trim - top
right corner outside. I'd stick a small (wire) probe in the opening
and see how deep it is. Driving rain may be entering there. so it
needs to be caulked with a paintable exterior acrylic caulk.

The screws on the wood piece under the door can be adjusted up or down
for a tighter seal.