Hoping to help protect an IT installation, I've been looking into physical protection systems, specifically Access Control for protected areas. The field is quite big. Are there any US or International Standards on the subject? Any implementation guidelines?
So when it comes to security standards for physical security, I would recommend looking over the Department of Defense. Here's a relatively recent posting, but if you've ever spoken with anyone in their IT, they've got literally millions invested in the R&D behind security both physical and IT. Here's a (rather dry) read on the subject. I'd specifically recommend Enclosure 4: Physical security planning.