I am trying to install the following door threshold on a concrete slab. The door leads outside and the old threshold was rotted from water penetration. The following pictures show the concrete subfloor and the rotten threshold.
The person that installed the old threshold first placed a bunch of caulk directly on the concrete slab, then placed a sheet of plastic over that, and then placed the threshold over the plastic and held it in place against the door frame with some staples.
I believe that the plastic might have contributed to the rotting by trapping moisture. Is the correct way to install the threshold to the concrete slab to:
Lay down a bead of caulk (I have the DAP Alex Plus) at the very edge of the slab to prevent water from running under the threshold,
Add more caulk to the rest of the underside of the threshold and put in in place on the slab,
Fasten the threshold to the concrete with screws?
And should I leave the plastic sheet out of all of this?