I live alone in an old house. It was built in 1905, and is situated in a historic village in Upstate NY.
I work long hours, usually from 5am until 6pm at night +/- driving time. So I usually don't get to enjoy sleeping in during the week.
Well during the weekends, I make it at habit of sleeping in until at least 8 or 9 am. During these "sleep ins" I have noticed that around 6am, I'll get woken up by a slight scratching noise.
Assuming it's Professor Moriarty, my cat, I just close my eyes and smile, knowing I don't have to be anywhere. Then I hear her purr, and realize she's next to me, not making the scratching noises.
So I sit up. scratch scratch scratch. I realize it's coming from the wall behind my bed. I think alright, well I guess there's a mouse in the wall, or perhaps something else. I uneasily lay back down and just pull the covers up to my nose.
All sudden there's a loud SIGH and a huge bang, like a door being slammed shut. It's at this point that I'm already in the corner of my bedroom, holding a baseball bat, intently listening for anymore movement.
There will usually be one or two more SIGH's and a bang, and then nothing else for the rest of the day.
I still have no idea what it is.
tl;dr When I try to sleep in on weekends, there's scratching, banging, and sighing going on in my empty 105 year old house
edit- Alrighty here's the specs-
No central heating, I use space heaters instead (no, it doesn't cost me an arm and a leg in electricity :D).
The plumbing goes from the kitchen to the bathroom to the outside.
The water heater is outside by the propane tanks on the outside of the building (propane tanks are empty, as the downstairs furnace runs off of them, but propane is expensive, man).
I'm used to living in old houses, and I know what old house sounds sound like (say that 10 times real fast!!!) and it's definitely something else.
Edit 2: I know most everyone here says its squirrels and raccoons building broad swords and sighing in my attic. Well, I will record this noise and let you be the judge. Expect an r/askreddit post on saturdayish with the soundfile. I'll upload it to Grooveshark. Does that work for everyone? I'm not claming its ghosts, but scratchy sighing things creep me out anyways.
Edit 3: Ok. Forget grooveshark!!! I'll do youtube. I'll make you guys a movie. Expect a plot. Professor Moriarty will be involved. Skip your saturday morning cartoons, and grab yourself some Saturday morning News_and_coffee