Even if local code requires the availability of building plans it might still lack the interior design plan.

In some places interior design changes doesn't require new permits or submission of plans, interior design usually includes interior, non load bearing, walls, doors, internal staircases and in some cases even external windows.

So it is critical to have the latest plans if you are planning to storm a building but like @Brian Knoblauch wrote- good luck finding those.

Using the Sweden example above [this][1] says:
"Du behöver inte bygglov för att ändra rumsindelningen eller göra någon annan inre ändring"

translated by google to 

"You do not need planning permission to change the room layout or make some other internal changes"


  [1]: http://www.boverket.se/sv/byggande/bygga-nytt-om-eller-till/bygglov/