In order to keep things in context, we must remember that Prohibition started in 1920 and ended in 1933.
My family home wasn't built until late 1933, so I doubt there would have been a secret room for a hidden still (or bathtub for gin), a disguised bar, etc. included in the plans!!
Regardless, the concept is fascinating! (I recall other threads about eating establishments/social clubs in the Outside Lands that served illegal liquor, and the pains they went to hide the fact...but that's not the same as private homeowners cheerfully thumbing their noses at the Volstead Act!)