Hi there.
Finally, I’ve found a solution, maybe it isn’t the better, but for me works fine.
I’ve added this code to my custom.scss or custom.css stylesheet:
#g-page-surround {
padding-bottom: 10rem;
}
#g-footer{
position:absolute;
bottom:0;
left:0;
width:100%;
}
With this option, in pages with few content, the footer in Gantry allways keeps its position at the bottom of page.
I hope have helped.