It depends where you live and what the building codes in that area try to address. Here in Tokyo the biggest worries are earthquakes, so my apartment walls usually incorporate wood instead of concrete and the 5GHz signal through my closed door and six layers of rooms only just drops to 2/3 on my phone.
Unfortunately, this also means I'm competing with nearly a hundred different APs in the apartment alone - of which many broadcast in both 2.4GHz and 5GHz - to the point that my Macbook less than a meter away from the router still takes a hot minute to automatically find the AP unless I manually select it.
Unfortunately, this also means I'm competing with nearly a hundred different APs in the apartment alone - of which many broadcast in both 2.4GHz and 5GHz - to the point that my Macbook less than a meter away from the router still takes a hot minute to automatically find the AP unless I manually select it.