I have used polyurethane foam to cover a 5 cm (2 inch) horizontal gap between a metal door and the ground. Polyurethane foam , as I know , needs to be covered with cement in order to withstand the corruption. In order for cement to apply I am going to use a metal frame. I am not sure how to try to stuck the metal frame to the foam in order to be able to use the cement then.
Below is a photo to get a better idea.