text: I think the only thing missing here is fence_type. You can set whichever you want. Why do you need such detailed mapping: wall and fence at the same place? Where did you see a fence mapped together with a wall at the same place? And on which map I can see that?
  
  Anyway, even these two ones:
  https://wiki.openstreetmap.org/wiki/File:Seeboden_Kraut_Rumpler_2012_a.jpg
  https://wiki.openstreetmap.org/wiki/File:Waziers_-_Presbyt%C3%A8res_fran%C3%A7ais_et_polonais_de_l%27%C3%A9glise_Notre-Dame_des_Mineurs_de_Waziers_(32).JPG
  are tagged as barrier=fence + fence_type=concrete.
  https://wiki.openstreetmap.org/wiki/Key:fence_type