Here is a diagram which shows how to make a bog standard cardboard dolls house with four rooms and a slightly interesting roof. The most fun you can have with a cardboard box, in my opinion. The stronger the cardboard the better but you will usually find that your horizontal floor needs an extra cardboard floor adding for strength and to stop it sagging. No glue required. No paper fasteners required (though I am trying to find a way to work them in) just slots cut in the walls and the partitions so they fit together.
Check out the printables and patterns section for some free dolls house scale wallpaper to decorate your cardboard house or keep an eye out for future blogs posts with more decorating ideas.