I assume they built the foundations with expansion in mind. Or they used Nerf for the upper floors.

Says the card’s official motto: “Once a guest you will want to come again.” Basic, but typical for the 20s. The card was mailed on July 15, 1927; it either says “just taking train for Mich” or “Just laluig hair for Mich.” Signed, Bill, and sent to Della Nelson in Mayville, North Dakota. The blot on the card is not his room – that was made by the postal cancellation.

Or Bill was sleeping in the space between the floors, which is entirely possible; that's where you find the hair to laluig. Mich says so, anyway.