This is some boilerplate code to take the content of a WP Query and split the posts into relatively evenly distributed rows and columns.

loop-rows-cols.php

<?php
$args = array( 
	'post_type' => 'post',
	'posts_per_page' => -1,
);

$posts_loop = new WP_Query( $args );	
if ( $posts_loop->have_posts() ) :
	// Initialize Output
	$output = '';
	$started_last_row = false;
	
	// Set current counts to 1
	$cur_row = $cur_col = $cur_item_count = 1;
	
	// Get total items in query
	$total_items_count = $posts_loop->found_posts;
	
	// Set number of rows
	$num_rows = 4;
	
	// Set number of columns
	$num_cols = 3;
	$grid_markup = (int) 12 / $num_cols;
	
	$row_start = '<div class="row">';
	$row_end = '</div>';
	$col_start = '<div class="columns medium-' . $grid_markup . '">';
	$col_end = '</div>';
	
	// Determine the number of items per column
	$items_per_col = ceil( ( $total_items_count / $num_rows ) / $num_cols );
	
	// Initialize loop index
	$i = 1;
	
	while ( $posts_loop->have_posts() ) : $posts_loop->the_post();
		
		// Check to see if we're in the last row, we might need to do some balancing
		if ( $cur_row == $num_rows && ! $started_last_row ) {
			// Count the items remaining
	        $items_remaining = $total_items_count - $i + 1;
	        
	        // Determine the new number of items per column
	        $items_per_col = ceil( $items_remaining / $num_cols );
	        
	        // Signal that we don't need to do this again.
	        $started_last_row = true;
	    }
	
		if ( 1 == $cur_row && 1 == $cur_item_count ) {
			// START ROW
			$output .= $row_start;
		}
		
			if ( 1 == $cur_item_count ) {
				// START COL
				$output .= $col_start;
			}
		
				// echo item content
				$output .= "here's my item content";
		
		
			if ( $cur_item_count == $items_per_col ) {
				// END COL
				$output .= $col_end;
				
				$cur_item_count = 0;
				$cur_row++;
			}
		
		if ( $cur_row == $num_cols + 1 ) {
			// END ROW
			$output .= $row_end;
			
			$cur_row++;
			$cur_row = 1;
			$cur_item_count = 0;
		}
		
		// Check to see if we're at the end of our items and close everything
		if ( $cur_row == $num_rows && $i == $total_items_count ) {
			// END COL
			$output .= $col_end;
			
			// END ROW
			$output .= $row_end;
		}
		
		$cur_item_count++;
		$i++;
	endwhile;

endif;