When I was struggling to get a signal through 4 damp redbrick walls, I finally used a USB device which had a flip up lid that you aimed here or there.
I also downloaded inSSIDer 2.0 (free) and with this I could swing the aerial to the best advantage. Small changes made a huge difference, not only in the signal, but in the ratio of strength against neighboring users.
A pal of mine uses one of the mains-born gizmos in a huge old house. Perfect.