All speakers in the same system are visible to all users of that system.

You can however have multiple systems on the same network.

In theory, as I’ve never tied this, you could separate the 3 floors into their own separate system per floor.

Each system would only be able to control the speakers on that floor and in order to control speakers on a separate floor, they would have to “switch system” in the app.

However, separating speakers into different systems may cause streaming issues depending on how music is currently being streamed to the speakers on the 3 floors. A music service with only one account may restrict streaming to only one system at a time.

That’s great! We don’t care about streaming, we only use radio stations. How do I setup multiple independent systems on the same network? through the app, I can only see one main system

Thank you!

I think the easiest way to create separate systems, without having to factory reset speakers, would be to power off all speakers, leaving only the speakers powered on that you wish to be in one of the separate systems. 

Then, use the Transfer System Ownership option in the app (I believe you have to sign out the app for this to work) to temporarily transfer those speakers to a separate Sonos account (you will need to create an account using different email address). Once the respective speakers are registered under the new Sonos account they will be a separate system, you can then again use Transfer System Ownership to register that system back to the original email being used. You can then power off those speakers and power on the speakers you want in a separate system. You may have to reset the app, then join existing system. Once the respective speakers are visible in the app, follow the same process. Once done, you can power on all speakers and the original speakers that have never been transferred should be the 3rd available system. 

Then app should then be able to discover the 3 separate systems on the same network and be able to switch between systems in the app.

Bit of a long winded process, but I believe that should work to split the existing system into 3 separate systems.