Ours are at 5'. I sometimes wish they were at 4', but since I didn't have to do the work, I won't complain. If I remember right, 5' is about right for those areas that don't have to worry about snow load. Don't forget the purlins (pipes) that will help with holding together when the winds blow.

Vicki, how cold are you getting tonight? I'm in southern IL and am thinking about visiting AR before we go home this weekend.

We will get down to thirty two tonight We've been hovering at frost at night and between fortys up to sixty in day depending on sun. They're predicting a little. Cold snap this weekend. Mid 20s. I hope my brocs do okay

I use 4' centers. 5' or 6' works for some people, too.

I just built a high tunnel with 4' high side walls. It's 18.5' wide. My hoop is 21' and my peak height is 8.' The lower your height, the easier it is to handle strong winds. 12' is really tall. If you don't need that height for the sake of fitting a tractor inside the high tunnel, you might consider using shorter hoops to give you a lower structure. That would make it much stronger against wind.

Having built 4 PVC tunnels and I am still using them, consider dropping that space down to 3 feet. It will make it much stronger, especially with 1 inch pipe. If it was 1.5 inch pipe, 4 feet would be ok.

Jay

Let me clarify, my hoop house is metal NOT PVC. Makes a big difference.