I am turning a wooden shed into a chicken coop. Is there anything I can use to waterproof the interior so that it can be hosed down from time to time without having to worry about damage/mold? Thanks!
I have no suggestions about how to coat the interior so it can be hosed down. I do have a warning that you must not have a vapor barrier on both the inside and outside of any of the walls, ceiling or floors. You can easily trap moisture in the resulting sandwich and cause wood rot. What you can do here will be dictated by the details of the construction and the climate.
I suggest that you look at how small chicken houses are traditionally maintained. Tradition isn't everything, so check with close by Land Grant University (ag school) web sites to see if they have any advice about maintaining chicken houses.