As well, is the router to laptop path perpendicular to the walls or at an angle? I've found this to make a big difference. There are some published approximate loses (measured in dbi) for certain materials such as wood, concrete, drywall, etc. that you might want to look up. It wouldn't be unusual to lose 1/2 your signal through a single cinder block wall, for example. You can also experiment with using different channels. Another nearby router or AP on the same (or near) channel can interfere with your signal. You can try channel changes, router relocation (make a more perpendicular path) or antenna adjustment for best signal.