On my recovery project in Apple Valley, the back door threshold was loose, and kept making a racket as we walked in and out. When I got to checking it out, I found that the subfloor underneath was rotted away and couldn’t hold it properly, AND, it was undersized.
I picked up a new threshold at the hardware store, and got the old one out to see how bad the subfloor was damaged.
I took all the old rotted stuff out, trimmed it out very neatly at the edges with my Oscillating tool, then trimmed some new pieces to go back on the joists, which were in fine shape.
I cut two pieces that would meet in the middle so I could be sure to get the ends of the board underneath the door casing without having to remove the casing; the owner was quite impressed!
I got it all lined up nice and neat, screwed in on both sides, and most importantly, not rotted! Last, I installed the new threshold, and adjusted it so it would fit snugly underneath the door.
Now when you close the door, it’s a snug fit with no drafts, AND, the threshold protects the siding piece underneath it, too!