We've had residential customers with a lot of 'blockage' and limited wireless abilities before, and sometimes we've used those PowerLine adapters instead of fighting with WiFi extenders, their password-sync-up and timing issues.
For example, the Wireless Router is in Room 1, and Room 3's computer has a kitchen between it ("Room 2"). Microwaves, freezers, fridge, tiles and stone work, ovens.
One good thing about the PowerLine adapters - they pretty much work out of the box OR THEY DON'T. We plug one into Room 1, hook it to the Router's Wired Port, then take the other Adapter into Room 3, plug it in and see if the SYNC light goes solid after 2-3 minutes. If it does, bingo, it works. If not, forget it and keep thinking of "Wireless Extenders".
The 'kits' are usually $100-120, but we get a kit, take it to a home and try it out. If it works, a good solid solution. If it doesn't, return it and get our money back.
Wireless Extenders can appear 'flakey' because of ?? the differences of radio-chip generations ?? There's a timing issue, too - some of them take minutes to 'sync up' to the Main Router. Sometimes this Sync-Up doesn't occur, other times it's fine. That inconsistency isn't much fun. Then, if you've got a password protection (WPA, etc.) on your wireless router, you've got THAT issue to deal with for the Extender too.
But that trick is usually "Disable all security from original Wireless Router first, then get Extender to function in an open, unsecure network. FIRST."
Then, go back and set up Security again on the main Router, then mimic that on the Extender.