You may need a cricket behind the chimney to provide drainage for water that accumulates on the roof. The cricket is a small sloped structure that diverts water away from areas where it could cause damage, such as along the sides of the chimney. It also helps prevent water from pooling around the base of the chimney, which can lead to moisture problems.

Additionally, having a cricket behind the chimney can help reduce staining and discoloration of the masonry in this area. By diverting water away from these surfaces, you can help keep your chimney looking its best for years to come.

Finally, if you have an older home with a brick or stone chimney, installing a cricket behind it can help protect it from weathering and other damage caused by moisture accumulation. This will help ensure your chimney remains structurally sound and in good condition for many years to come.