Restoration: to preserve
Restoration aims to preserve a building's historic and architectural value. Intervention is kept to a minimum, original material is retained wherever possible and every action is documented.
Renovation: to update
Renovation adapts an existing building to current expectations of use and comfort. Design freedom is wider, though the building's character can still be deliberately retained.
Which is right?
The building's protection status, its condition and the owner's goals decide. Some projects combine both: the façade is restored while the interior is renovated.

