In the early 1990s I moved into a small 3 bedroom house on the east side of Athens, Georgia while attending the University. I ended up living in the house well after graduating for a total of about 9 years. During that time I had a number of roommates come and go. Odd thing is the house was new when we moved in so it had no history to account for the experiences that occurred.
One of the first unusual events I remember happening is an occasion when I was walking past the kitchen which was to my left (the kitchen had a cut-out opening with a counter top which faced the living area). As I passed I heard a loud "clack" of something hitting one of the bar-stools and realized that a small glass bottle that had been on the counter top had evidently come off the counter, hit the bar stool and landed on the floor in the living room next to where my roommate was sitting. We both were bewildered as the bottle had come way too far to have just fallen and since it was a square bottle it would not have rolled to where it ended up. I definitely had the sense that it had been thrown at me as I was walking by.
In those days the University was still on the quarter system and once finals were over the first week of December there was about a month without classes. My roommates went home for the break but I had a job so I stayed alone for that month. One night I woke up to the sound of my dog growling. She was looking out my bedroom door into the house as she continued to growl. I peeked out but saw nothing out of the ordinary in the dark. I tried to get her to come out with me to investigate but she dug her feet in the floor and refused to budge (this was very unusual for her because for a lab she had an aggressive personality). I crept to the kitchen and got a knife, quickly looked around and went back to bed, locking my bedroom door. Can't swear this was paranormal but it definitely stuck with me.
Over the years a number of other things happened, often several things happening close together then no activity for a long time. Radios would turn on, a growling noise in the front bedroom, one roommate reported seeing a shadow figure. Shortly before I moved out I was vacuuming and noticed a hand-carved lion statue was turned facing the fall. I realized that I had had to turn the statue around several times before but this was the first time I wondered why it kept happening. I fixed its position and continued vacuuming, making a circle around the table. When I got to the other side I looked up and saw the lion was again facing the wall.
Although the activity seemed to come and go, what I remember most is how heavy the air seemed... It had this hard to describe weight to it. Often at night when I was trying to go to sleep I would have a strong sense of dread that I couldn't explain. When I would try to pin down the feeling or what was causing it I just came up empty. This was particularly true when I was using the front bedroom, the same room one roommate once told me gave her nightmares.
I wish I had known about EVPs at the time, I would be curious to see what that might turn up. Also, not sure if it's worth mentioning, and I don't really have the sense that there is a connection, but for much of this time I worked in an old (1800s) supposedly haunted building on campus where I had two paranormal experiences.
Also you mentioned that you work in an old building... You may have had a ghost become attached to you.
I hope you find more about the ghost and I'll be waiting for more of your experiences. Placing you in my faves.:)