
Hey Alex,
What you could do is fire it manually once the modal even open even is firing. So something like that:
$( '.yourModalSelector' ).on( {
'show.uk.modal': function() {
UIkit.grid( 'yourElement', { /* options */ } );
}
} );
Have fun,

Thank you! for the moment, i have managed to have all the boxes with the same height, but it will be usefull if it changes. and if i want to implement the parallax i have also to do it the same way, or for any js element that i want to have to the grid (scrollspy for ex) ?