Interesting to see different permit requirements!
Austria has 9 different construction codes (lovely for a country with just 8 million inhabitants) but in the areas I know you don't need permits for any work that does not alter the exterior appearance of the building. Minor exterior work such as adding or replacing windows, replacing an existing roof with same (i.e. without altering the shape of the framing, the roofing material can change) etc. are covered by a simplified process with is called a construction notification rather than a permit - you just tell the council what you're going to do in an informal letter and if they don't object within 6 weeks you can start.
In theory, anything but (possibly) painting is supposed to be done by professionals who are responsible for the compliance of their own work. I've never heard about issues with homeowner work though, as long as it's safe. If DIY wiring burns down the house or electrocutes something (which happens considerably less often than you'd expect seeing some of that stuff) it DOES become an issue of course.
On a side note, even painting can be dangerous if someone is stupid... 1 or 2 years ago two families barely survived a weekend of painting, because one guy had the insanely bright idea to move the charcoal grill into the living room overnight to make the paint dry faster!
