I am planning to replace the plank door in the basement with a proper exterior door. The basement floor is about 12 cm lower than the ground outside. Outside, there is a concrete slab with a drain for runoff. The threshold is cast and protrudes about 2 cm above the outer slab, but it is not as wide as the opening. Instead, they have allowed the door frame (frame and frame, just a regular stud) to go all the way down to the basement floor. Of course, the wood has become rotten. However, I haven't seen any water running in, but it will probably happen at some point.
I plan to cut away all the wood that is below the level of the threshold and a bit more, build a casting mold that goes all the way out to the wall in lightweight concrete, and is a few centimeters higher than the current threshold. That is to say, I want to cast a new full-width threshold that is also cast over the old threshold.
Do I need to reinforce? I was thinking of cleaning all the contact surfaces with a steel brush first. Should I drill some reinforcement into the old threshold? The cement will be cast against the lightweight concrete. Perhaps a bit vague description, but does it sound like a good plan? Otherwise, I can try to explain better. Attached is a picture of how it looks today.
