I think this is a copperhead, but since it is dead you could look at the anal plates as described in this article to confirm.  Also, if the dark, hourglass features are thinnest at the top of its back and widest on the sides, it is a copperhead. However, copperheads are found everywhere in our environment, and they seldom bother people unless they are aggravated or stepped on.  Keeping animal and bird feed away from the garage, and dealing with mouse or rat populations is the best way to keep copperheads away - they are just looking for food. Also, keeping low growing plants (like English ivy) cut down and moving brush piles to areas further from the house will discourage their visits. They like cover when they move about.  But in general, I would not be overly concerned at finding one copperhead, they common in this environment. 

http://www.virginiaherpetologicalsociety.com/venomous-look-a-likes/copperhead-look-a-likes/copperhead.html