living situation

So living with someone you've never met before is interesting.
We stay out of each others way most of the time and hide in our respective rooms. He's a nice guy and when we do run into each other we have polite conversations about stuff. The other day he even brought me to Ikea to get to my desk, that was really cool. But when you live with someone you pick up on some weird habits. Well, he slams doors.
Yeah, i dont really get it, at first i thought he was mad all the time but I guess he just doesn't know his own strength. It's a bit unnerving though because I hear him slam the door and I think "Is he mad this time?"
Damn! He just did it again. why do you have to slam the doors all the time? Just mellow out man, you're stressing me out and weakening the Integrity of the building.