Why does the floor creak at night?
All matter—gases, liquids, and solids—expands when heated and shrinks when cooled. This principle explains some of the funny and unexpected sounds that your house makes at night. During the day, the Sun’s rays warm the materials your house is made of—like the wooden frame that supports its roof and walls—and they expand. Heat from the Sun may also make the interior of your house warmer and even shine on some of its furniture. When night comes, the temperature outside can drop 30 degrees or more as Earth turns away from the Sun. Things like wooden floors, house-building materials, and furniture become cooler, too, shrinking and slipping a little, which can sometimes cause creaking and groaning sounds. These noises are particularly noticeable at night because your home and neighborhood are so much quieter than they are during the day.