Plenty of times. There was one I never saw the finished stages of that was basically an entire apartment accessible only by a small hatch in a closet. Either the homeowner was planning to harbor criminals, or a mistress, a man in an iron mask, or just really wanted to be able to get away from his family. Hope it wasn’t like an HH Holmes thing.
Did a lot of mansions and this wasn’t insanely common but far more than I expected. There was one builder that did a lot of these houses who managed to find a retired electric chair that he kept in a hidden room. He ‘joked’ that when his kids were bad he would make them sit in it for few hours. It didn’t have power running to it but still.
Not a secret room, but a friend of mine had a weird compartment in her house. In the middle of the dining room, there was a door that was about half the size of a normal door, maybe about 3 1/2 feet tall, same style as the rest of the doors in the house, knob in the same place halfway down as any other door. It led to a room, about 3′ x 5′, same height. It came wallpapered and carpeted similar to the rest of the house, but definitely intentionally decorated–my friend and her family never changed it. It was just this weird, half-sized room/finished crawl space.
Yeah, working on a big house that this eccentric couple owned, there was a secret underground Olympic swimming pool, we installed a pool table that came out of the ground floor. Basically dug a big hole, some other dudes sorted all the pneumatics and electrics. Don’t know what the table looked like at the end, but his swimming pool was dope.
My house has two secret rooms and here are the photos of it in construction (almost finished). It is off of my movie room behind one of two black velvet curtains.
The main secret room is huge (20 foot by 9 foot), large enough for five or more people to escape tornadoes.
Ceiling and walls are 18 inch thick concrete. The ceiling also has a steel roof with 10 inches of concrete poured atop it.
All wired, vent and return, internet wired. Nothing wireless works in this room. We some times call it the black hole because the bars on your phone just disappear when you enter.
The room is finished now and decorated (like rest of house). It gives it less of a creepy vibe. Enjoy.