ᐅ How flexible is a building permit / planning permission?

Regarding my extension and the thread about symmetries, I have a question about building permits in general. How flexible is such a permit? In other words, what changes can be made without involving the authorities, risking a penalty, or failing to receive final inspection approval (completion certificate)? For example, the width and height of the windows—if they are built 10cm (4 inches) wider than planned? These are rather minor adjustments that don’t drastically change the overall design.

If larger changes are necessary, does the permit need to be renewed? Or is the authority simply informed?

Just to avoid any misunderstanding, I don’t have any plans for changes myself. I’m asking purely to gather information and for future reference.

You can do quite a bit with a change order. It costs around a hundred (or so) and doesn’t take as long as the approval itself.

Building height, setbacks, exterior colors, etc., should be handled through this process—basically anything that relates to the zoning plan or state building regulations and might deviate from them.

Moving a window, making it 20cm (8 inches) larger or smaller, or any changes that only affect the floor plan and layout are generally not of concern to the building authority.