Difficulty explaining to my boss that I'm busy

I'm a local site sysadmin for a manufacturing company that is currently under construction, and for some odd reason, my direct manager is the service tesk team leader. I've started butting heads with him because I feel he doesn't understand my workload.

He has a tendency to manage me and my work like I'm fresh off the 'What are computers 101' course, but I have nearly 10 years of experience and am currently wearing multiple hats, only one of which would fall under his scope.

He regularly pings me for leaving tickets open longer than a week, and despite me explaining that the building for that ticket literally doesn't exist and won't be built for 6 months, he hits me every single week to update it 'For the users benefit, you know, so they're updated'.

I'm really having a tough time figuring out if I'm approaching the situation the wrong way, or if I'm being managed by someone who thinks I'm an 18 year old level 1 service desk agent.

Has anyone else run into this? How did you handle it?