layout-wrap leaves spaces in column

I am trying to create pinterest like layout. I am able to list all my cards. I am using below code.

`
<div class="layout-row layout-wrap">
{{#each model as |item|}}
<div class="flex-45"> {{#feed-small class="col-xs-5" feed=item}} {{/feed-small}}
{{/each}}
</div>
`

My cards are listing properly for cards with same height. When i receive cards with different height it leaves blank spaces