Beginner problem - sections, I must be missing something obvious

I’m trying to create a few sections but for some reason I don’t understand there are no pages generated for the sections. I have the following layout

   +-- en
   +-- se
   +-- twr
          + cs

This site doesn’t contains any blog posts but should only contain pages. The en/se directories seem to work perfectly and I get pages in English/Swedish and I can select what to use. However, the ‘twr’ section isn’t rendered at all (these are pages without any translation what so ever, it should just be a section for specific topics). If I move this section to the ‘en’ the pages are rendered and I get my ‘twr’ directory.

English is the default language for the site, does this mean that all sections I want to have should be created as sub-directories to the ‘en’ directory? Should the top level be “language directories” only (if not, what could be the reason that the ‘twr’ directory isn’t rendered)?

As you can see, I’m slightly confused.