Using @span for grid

grid.scss

    &.columns{
      /* Layout options */
      @for $i from 2 through 8 {
        &-#{$i}{
          $value: 12 / $i;
          .grid__image--item {
            @include span( $value, 12 );
            &:nth-of-type(#{$i}n+#{$i}){
              margin-right: 0;
            }
          }
        }
      }
    }