That is the default theme design unfortunately.
The workaround we came up with was to use a child theme to solve that problem. The now deprecated but still good as a starter child theme FourteenXTD available here: http://wpdefault.com/fourteenxtd-child-theme/ has code in it for that particular issue.
For a fully fledged child theme with more options you can try out the Sequel theme available here: http://wordpress.org/themes/sequel
Hopefully either one of them will help you address that issue satisfactory :)