@Oskarek: Vision (and thus ranged attacks) is checked by doing line traces from the attackers tile at “visibility trace height” (by default head height of the UE4 mannequin) to the same height on the target tile. This trace is done on the custom trace channel “Range trace”. To block vision there must thus be something blocking “Range trace” between the start and end Points of the trace. So you can for instance set the mesh of your building to block range trace (make sure it has an appropriate collision volume and collision enabled). You can also create a copy of the invisible wall tile and set all its edge costs to 1 and Place them wherever you want to block vision. Or just drag collision volumes into the viewport wherever you need them.