[MT-AU Public] Wifi blackspot coverage improvement

Hey, I've got an RB951G-2HnD doing routing & wifi for my network. It's doing a great job. I'm in a very old house with double-brick internal walls everywhere, and I've got a black spot out the back I want to get better coverage for. What's the best option if I want to stick with Mikrotik gear? (Which of course I do :) ) - Ben