You should first have the written consent of the landlord before bigger renovations. Minor changes are allowed as long as they do not cause damage to the apartment. The modification must be easily undone. Individual holes in the wall or portable, removable items that can be bolted count as such minor changes. One speaks of a structural innovation only when the structures of the dwelling is altered by the renovation work. This is the case when a door passage is enlarged or a wall is torn down.
The landlord may renovate and rebuild, but must take consideration of your needs as a tenant. He must also inform you about the work process. During the period of reconstruction, the tenant is entitled to a rent reduction. The landlord can not refurbish during a termination period.