Possible to prevent iPhone from automatically joining known networks?

The Wi-Fi settings description of "Ask to Join Networks" says "Known networks will be joined automatically...". That "feature" is causing me problems.

I have a local wi-fi router in my home office which is above the garage and far from the family room at the other end of the house, where there's another wi-fi network with a different name. If I ever leave my office and walk towards the family room, my iPhone jumps to the family-room network but it doesn't jump back on to my office wifi network when I return to my computer. When I'm in my office, the reception for the FamilyRoomNetwork is very weak and it is very slow.

Can this be fixed, either by causing an automatic rejoin of my office wifi network when I return to my desk or by forcing the phone to ask my permission to switch to another known network?

P.S. I do want to join the FamilyRoomNetwork at the end of the day, so I don't want to remove it.

Go to the wifi network info , there is a a choice « auto connect ». You can configure auto connection network by network