I want this, but 5GHz doesn't permeate the walls in my bedroom as well. :( I figured we'd be living in a dual-band world for quite some time.

Weren't mesh wireless networks made to help this issue?

Also 802.11aX is out soon, it will use 2.4/5ghz just with a bit more bandwidth on both, so you may want to just wait for that instead. (edit: looks to be maybe +25% or so more)

I had the exact same propagation issue as you. Fortunately, I found a solution that's both inexpensive and incredibly effective.

http://amzn.to/2AgqfsI

A drill bit for wood... for drilling through walls? Wat?

We just leave all our doors open!

Sadly there are other things (proprietary or Bluetooth wireless accessories, for example) that only operate on 2.4GHz.

makes me wonder if the problem was accidental.