I think it's a type of Sedum. Do you have a photo of the flowers. ? It might be easier to identify with the flowers.

I have not had any flowers on it yet. It was grown last year from a small piece, which I found growing out of a wall on the way home from work one day.

I have something similar which was growing on a wall. It's a Sedum.

I think it might be blue stonecrop or Sedum reflexum but I'm not 100% sure. It's very pretty.

I have some thing simular to this it is a sedum of the Alpine family I think I have tall yellow flower from mine. Good ground cover to surpress weeds which I use it for