Do I have to use them if I'm building directly on a perfectly level, completely intact, 2' thick concrete pad? I wasnt going to use them, but the concrete pad stays damp because its in the shade most of the time during the summer. Now I'm wondering if I should have the ventilation under there? OTOH, I dont want to have to worry about something (an opossum or any other rodent, for example) deciding to live under there which means I'd have to find a way to secure hardware cloth under the coop.