While sometimes there are limitations in the ability to install or securely affix a safe to your premises, Safe Central will always recommend installing your safe to increase its ability to resist forced entry and removal.
While concrete and/or brick structures will provide the most secure anchoring, you will still dramatically increase the security of your safe by securing it to steel or even timber structures.
Make sure to use quality fixings and have them installed correctly to maximize the protection offered and seek professional assistance from a police licensed safe installer if uncertain.