Add non-background space between header and center column

I have a background tile for the #header space and one for the #middle space. I want to create a bit of separation between the two so that the body's background image is visible. I've tried adding padding and margin to both but all those do is extend the respective space with the background tile (i.e. adding padding/margin to #header simply extends the #header background tile rather than create a blank space). Is there a CSS way to do this?