there is a thick, concrete, steel-reinforced wall running though the middle of my flat. it has been the same on my previous flat. while it does not matter much day to day, one thing that used to be a bit annoying was wifi signal strength. with my AP set to 100% power, signal was just enough to browse the web, on the other end of the flat. that was 2.4GHz of course. you can pretty much forget about (usable) 5GHz. while you can buy more powerful APs and more sensitive end-user devices, “bugger hammer” was not the option for me.
it turned out there is a good, standard-compliant solution to have multiple APs at home, serving the same network, with IEEE 802.11r-2008 wifi roaming. it is not exactly the same thing as roaming in cellular network – it is still very client-dependent. it does however work with any reasonably modern devices. i.e. my 5+ years old phone sucked when it came to wifi roaming. however it was kind enough to finally break and my “new” (2-3 years old) device work like a charm. same for all tablets and laptops. OpenWRT does support it out of the box. if you're in the same situation i am in – give it a shot. it does not break compatibility and allows to keep internet running, while roaming ones home. ;)