Force page layout (full width / content sidebar)

functions.php

/** Force full width layout */
add_filter( 'genesis_pre_get_option_site_layout', 'child_do_layout' );
function child_do_layout( $opt ) {
    if ( is_single() ) { // Modify the conditions to apply the layout to here
        $opt = 'full-width-content'; // You can change this to any Genesis layout
        return $opt;
    }
}