Profile: eWeb

Problem:
wrap all the rows in a wrapper to achieve min 100% height of "main" element, And only one function lets to do it - using grid system in layouts. But that have huge disadvantage - it adds gaps between columns with each inner grid added, which makes this hardly usable for my goal.
Solution:
1) the easiest way is wrap all the rows into a single grid cell.
2) Or you can simply edit your theme file, find the Layouts function the_ddlayout( ), and wrap it with what you want. for example:

echo '<div class="my-div">';
the_ddlayout( 'page-default' ); // Loads 'page-default' layout by default
echo '</div>';

Relevant Documentation: