Mulch storage

This season I am looking to get away from the high price of mulch and get bulk delivered. As far as getting a bunker setup for the mulch I've got that figured out. I was curious if I could make it a three sided barn so that I would have more space to get equipment out of the weather during the winter months. I thought on one side I could store salt there as well. I've got it stored elsewhere at the moment.

I just didn't know if keeping the mulch out of the sun and rain during the summer...

Mulch storage