Cardboard is cheap, light and temporary, and dream books read it as a makeshift arrangement or a situation not built to last. A cardboard house points to feeling that your footing is flimsy.
Does the traditional reading fit your dream, or did it mean something else to you?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.