If it s not what paul ward said water hammer which usually occurs when a water valve abruptly shuts off then it s probably temperature change in the attic.
Loud thud in the attic.
It is unrelated to plumbing usage or to start and stop of hot water heating system.
Heating ducts as they cool also make banging noises as do.
It happens irregularly almost like someone dropped a heavy weight or fell and the house shakes a bit.
It is very loud on the first floor coming from different places on the ceiling not so loud on the second floor.
If it s the fall or.
Sometimes two or three in a row a few minutes apart.
The thump occurs several times a day usually in the evening.
If you hear thumping in your attic at night it s most likely a larger animal such as a raccoon or opossum engaged in jumping from one area of the attic to another actively shoving or destroying something or dragging something heavy.
No that s not the sound of chains rattling in the attic.
There are a few possible sources for this sound but none of them ghostly or even worrying enough to call in the pros.