I think I got super lucky with my playhouse then. I got it for free and just added a floor, a door, and hardware cloth to the openings. Never have had a leak. We've also extended on it since this picture and it still stays nice and dry.
We converted a playhouse but as the girls grew (and chicken math hit us) we realized it wasnt big enough. We did lift it but the add on is big enough for me to stand in. Every time I post on here i realize i dont have a finished picture but here it is with the add on, it now has hardware cloth...