I live in a condo which was built less than two years ago. In the last two weeks, I have been hearing a loud clicking/banging sound seemingly coming from the first floor flooring or from the basement ceiling. It does not go off or on when the gas burner is working or when water is turned on or off. It occurs more often at night. It can last 2 or 3 seconds and up to 30 seconds. The HVAC repair person did not find anything wrong. It is loud enough to wake me from sleep. Any ideas as to what this may be?

The source of a noise can be really tough to track down when on site. On the web? Almost impossible, sorry.