Sort by Checkbox

I have the following code:

perch_content_custom ('Properties Listing', array (
    'sort' => 'sold',
    'sort-order' => 'DESC'
) );

'sold' is a checkbox within the multiple content template.

I am trying to order the items by the value of 'sold' , from 0 to 1, or checked to unchecked, but when I use the code above, only the sold properties are display, I've tried using 'sort-type' and mixes of 'filter' but none of these return entries where the checkbox 'sold' is not checked.

Does anyone know if it is possible to sort by checkbox value?

Running version: 2.4.9