First see PR for general tips → https://github.com/home-assistant/home-assistant.io/pull/18864 (latest revision at → https://github.com/home-assistant/home-assistant.io/commit/970295a277e8f01d3ee39eeeaacf453625b988d3 )
also of couse read and follow → https://www.home-assistant.io/integrations/zha#best-practices-to-avoid-pairingconnection-difficulties
Suggest buying one “IKEA Trådfri Signal Repeater” for each area to build a good baseline for the mesh:
https://www.google.com/search?q=IKEA+Tradfri+Signal+Repeater
Alternatively buy a few of ITead’s “Sonoff Zigbee 3.0 USB Dongle Plus” and flash them with Zigbee Router firmware → https://community.home-assistant.io/t/iteads-sonoff-zigbee-3-0-usb-dongle-plus-based-on-texas-instruments-cc2652p-20dbm-radio-mcu-now-sold-for-14-99/340705
Known limitation with Aqara/Xiaomi firmware. Only way is to manually re-pair device at final location.