To be fair, loads of years when a housemate is evicted that the rest of the group believed to be popular, someone pipes up that it can't be a real eviction and that they're moving to a secret house.

Although in this instance it was pretty obvious they knew there was a secret house. I don't think they've been in on the twist from the start but simply put two and two together when they heard Natalie and Ryan rowing. With Sam recognising Ryan's voice, and having already revealed that Ryan had tried countless times to get on BB in the past, it was obvious then and there that there was another house.

Most of the time there is a secret room.

indeed, just like the jasons ex when "she said we split up 3 weeks ago"


so over the past 3 months you was together u didn't mention the auditions for BB to each other

I'm sure the housemates heard rumours of a 2nd house being built before they even entered big brother so could have suspected a possible house.
And then them hearing the arguing over in the garden from the others.