I am creating a house that will have two levels and a loft space, and I want to create tags for each level so that I can work on them individually whilst still having the who house available to view. I select all the contents on the first floor and assign a tag to it, and I can switch this on and off fine. However, when I try for example to raise the walls using the push/pull tool it assigns its to the first floor tag. Not only this, but if I create the second level floor that covers the entire level parts of the floor are not visible if I turn the tag off for the first level.
It would be helpful if you share your model. It sounds like you are not using tags correctly. In SketchUp ALL edges and faces should be created and remain untagged. Tags are to be given to groups and components. The correct workflow would be to draw the floor plan and raise the walls, then make a group to contain all of that geometry and give the group a tag. Do that before you begin on the second floor.
How will you use this model of the house you are making? There are likely other things you need to consider.