A loud popping noise in the attic is often very common, especially when there are extreme temperature differences, such as large and rapid fluctuations between night and day temperatures. Also, when the temperature becomes very hot or very cold or when sunlight warms one part of a home and not another, these noises may become more pronounced. However, attic noises can happen at any time, though they are typically not a cause for alarm and are common phenomena, especially in older homes.
The most common cause of attic or house noises comes from the materials in your home undergoing changes as they increase or decrease in temperature. The materials used to build your home react when they absorb or lose heat. Because your home is built from different materials, different parts of your home react differently than others and may go through sudden, loud changes when the temperature fluctuates. If, for example, the ceiling joists are made of wood and the fasteners are made of metal, these different materials may expand or contract at different rates when the temperature changes. If any materials are resistant to movement, which many are, they may suddenly expand or contract, thus resulting in the loud noises.
The term "house settling" generally refers to the gradual movement process a home or structure goes through over time. Although a house settling is common, it is not generally responsible for popping noises or other such sounds. This phenomenon may give rise to cracks in masonry or foundation areas, as well as other places in your home, including the attic.
Sometimes loud noises in the attic may be caused by other factors not related to house settling or expansion-contraction issues. The noises may be due to roof damage, for example, or a pest, such as a raccoon, living in the attic space. If you are concerned about these noises, contact a home inspection professional for assistance.