I had a question on this caulking done on the outer part of the exterior door threshold. I have marked with the white arrow what looks like where the extension connects (seems to create a large gap that I am concerned water will form and leak from?) and a red arrow where the caulking is done. I'm curious if this will cause an issue with water.

Annotated image of door threshold

I was also wondering if this part of the door frame should be caulked as well. highlighted in white on the photo:

Annotated image of the corner of the threshold

  • I can't really see what I'm looking at in the first photo. In the second, isn't it already caulked?
    – isherwood
    Commented Apr 26, 2022 at 3:21
  • done - thank you Isherwood. As for it being already already caulked, yes it is but I have my worries if it was done properly as this is a new home for me and I have already found a few caulking errors. As for the first photo, theres just a very fine gap created from the extension that I am worried water could get into and somehow under the threshold. I wasn't sure if by caulking the exterior portion of the extension to the sill, if it would trap the water.
    – kevin044
    Commented Apr 26, 2022 at 13:16
  • The sill, and the stone below it, should be arranged so water flows away. If you seal the gap under the plastic sill that seal should never come into play. I'd be more concerned that the unsupported edge of the plastic sill will break eventually. I'd fill it with something solid, a strip of composite or hard plastic, to support it, and then maybe use caulk or whatever works to decorate it.
    – jay613
    Commented Apr 26, 2022 at 14:15

1 Answer 1


In my experience there's usually no caulk exposed on the threshold. It would look bad and fail quickly due to movement. One or more beads should have been applied underneath, and a threshold shouldn't be a drain plane anyway--there should be housewrap or membrane below, lapped over the wall sheathing.

The caulk joint at the bottom of the side jamb looks ok. I'm still not sure what has you worried.

Caulk should never really be the primary water management mechanism. It's highly prone to failure in that task. Any modern home has house wrap, window sill drain systems, etc. which handle that. Caulk is just a first line thing and is often mostly aesthetic.

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