The city came by last year and took a look at my haunt and approved. It is out doors and the walls are pallets screwed together with cardboard stapled to them to make a wall. They didn't count it as a structure because it had no roof. Think of it as an outdoor pallet maze converted to a haunted house, i use tarps as a roof like a carnival. Plus it's located on private property behind a locked gate. I simply meant in my previous post that you could use these materials to make some pretty elaborate props. If you are on public property you will have to be inspected by the city your in and get a permit to operate, and yes, just about any county in the US anything in the public domain with a roof will be considered a structure and subject under the city's jurisdiction including, a city permit to operate, compliance with all fire codes, and insurance.
I used to run a professional haunt with an old partner out of a vacant motel. 2 years of codes and regulations, not to mention insurance and payroll was enough for me to walk away and start home haunting and a year later my former partner called it quits and sold it off. you might have an easier time since your in PA, we ran it in California and CA has a ton of extra rules that other states don't have. Good Luck i hope everything works out well for you and if have any questions about building codes, props, or anything else just PM me and i will be happy to help out another fellow haunter.