What is the minimum distance between two civil airplanes parked in a hangar?
If you look at some civil-aircraft hangars, you will see that the planes are almost touching each other, as you can see here:



The planes are so close to each other to fit a maximum amount of planes into a hangar.

There are different types of hangars. Some are built just to store aircraft when they aren't used, some are built for aircraft-maintenance-operations and can even contain robots. Hangars can be simple buildings with a big and open space or they can be very complex facilities. 

If you want more infos about aircraft hangars take a look here.

You can find the minimum separation distances between aircraft and minimum distances between the aircraft and other obstructions here

Take a look at this table from this document (page 30):



As you can see, the minimum distance between the wings from two parked aircraft is not always the same.


  Dimensions vary for different models and configurations of aircraft.


If you want to find out the min. distance of an A380, you need to take a look at the documents provided by Airbus. 

No, there is no basic rule. The safe distance is determined by the aircraft-type, configuration and the hangar (owner).

If the airliners are stored in the hangar, they can be pretty close to each other. However, maintenance of a big airliners takes up a lot of space: