Metal storage structure for 20 foot long travel trailer?

My 32' rv trailer stays in a 16' X 40' X 14' interior height pole barn/metal structure with the long south side metaled down 40" off the ground for airflow.
The floor is 1" crusher run limestone.
I've always had tractor/implements shed and trailer sheds big enough for various sizes of non rv trailers.
The sun ruins every thing over time...long and short.