Looks like a ratsnake to me too. They can go right up the side of old barns and up trees (they like birds and chicks when they can get them). They can get big too. Our black ratsnakes here can reach 8 feet in length.
Just by looking at the snake, without having any close ups of the face. it is difficult to tell.
but just by eye balling the snake.....
i would like to say its about 7' total and probably about 2"s in girth if not more.
first guesses would be
Brown water snake *largest is recorded at 70"s*
Pine snake *can get up to 8'* and can vary in colors.
Midland water snake
Northern Pine snake
Southern water snake.