Structural

• Over the years, houses deteriorate structurally. Loose utility wiring can knock against the side of the house or a creaking in the roof may indicate some roof siding problem. Also, it's common for pipes and other metal objects to make what sounds like knocking as they are cooling down.
  
  

Mechanical

• Everyday conveniences, like ice makers, air conditioners, furnaces and dishwashers, are prone to make noises at unexpected times. They are the round-the-clock appliances that never really stop chugging away.
  
  

External

• There may also be external conditions contributing to house noises, like a tree branch scratching against a window during a wind storm. Another possibility is that a downspout, which is a gutter-pipe designed to catch and funnel rain and snow from the roof, may be out of alignment.
  
  

Weather Conditions

• When the temperature fluctuates, the wood or aluminum sidings of the house tend to expand or contract. On a particularly windy night, energy-efficient storm windows will also make a rattling noise, similar to the sound of a loose downspout, causing alarm.
  
  

Critters

• Aside from structural or mechanical issues, the creaking sounds could be a number of living things. Termites have a tendency to weaken the structure of a house, causing it to creak and groan as it shifts. Squirrels, rats and raccoons have also been known to climb through chimneys, walls, attics and basements, causing scuttling or scraping noises in and around the house.