Dunno if this will help your situation, but we put our chicken "house" on pallets....that helps a LOT for rain not getting in from under it....our problem is sideways rain.
Ick
...we have to change out all the hay bedding on the south side (well most all of the bedding),that is wet from our recent rains.
(north Houston area).
In fact, we're re-thinking how to keep sideways rain out...it's an open (4 sides) house, with only partial tarps on 3 sides...hmmmm?
Ick

(north Houston area).
In fact, we're re-thinking how to keep sideways rain out...it's an open (4 sides) house, with only partial tarps on 3 sides...hmmmm?