Your footer is fixed positioned and has no relationship with the rest of the page. You cannot account for the footer other than applying a fixed padding to the bottom of the body element.
e.g.
body{padding-bottom:70px}
Of course that assumes the fixed footer never exceeds its given height and the text in the footer does not wrap or all bets are off. That’s the problem with fixed elements and they should be used with considerable care and require good management.
At the moment you have an empty p element creating what space there is but this is not a good technique. The padding bottom on the body element is better but still smells of magic numbers.