Put mothballs all around the outside of your house.
Mind you that mothballs are considered dangourous, by means, they should be placed out of reach of children, and the fumes off of them can be toxic, this is why I place them outside.
I also have thrown a few in the basement.
I once had a snake problem, snakes would enter under the threshold of the doorway, and other various orfices in the house. An old timer told me to spread mothballs around.
So I purchased a box, and heeded to warnings on this box, and here it is 3 years later, havent seen a snake yet. Or couse it could also be that the last snake I killed, I mounted on a stick and posted it out in the front yard as a wanring to other snakes.

(I smile, but I really did that)