Carpet and tile are in: They are over a concrete slab. There is about a 1/4-1/2 inch space between the two/ How do I fill in the area between?

If the space is in a doorway area, use 1 1/2'' binder bar. U can get it in the carpet section of a big box store or carpet/tile store. U will have to install it with plastic mollies drilled into concrete.

This can also be done in the middle of room, but it will look like u made a mistake.

Chuck