Not every change is the same
Some corrections may not require changing the building permit decision, while others may require obtaining a decision amending the permit or carrying out another procedure. The assessment depends on the specific solutions, the regulations and the documentation approved for the investment. Do not assume on your own that a change is insignificant just because it seems small.
What to do before introducing a change
Do not introduce a change solely on the basis of arrangements with the contractor. Before starting works in a changed scope, give the designer a description of the planned modification and ask for an assessment of its impact on the design, the structure, safety, compliance with the regulations and the conditions of the decision.
When may a change of the permit be needed?
If the designer classifies the deviation as significant, it is in principle necessary to obtain a decision amending the building permit before carrying out such a change. In certain cases a different procedure may be appropriate, so each situation must be assessed individually.
How to reduce the risk
It is best to refine the key decisions at the concept and documentation stage. If a change appears later, hold back its execution until you have the designer's assessment and have established the required formalities.