As aart said, plan for any maximum snow load! Chicken wire will work pretty well to keep out hawks, but nothing else. You will need supports or the whole thing will sag and bag in no time, and hold ice really well too. I can't imagine myself crawling around in a 4' high structure!!! How about at least a center line of at least 7' or 8' poles? Your tarp will fail unless very well supported also. Mary