Chimney caps not only shield the inside of your chimney, but they are also designed to protect the cap area at the top of the chimney. The primary reason for capping a chimney is to protect the inside from water, which can lead to moisture damage. Damage also can be caused by dust and debris. Capping your chimney will lessen the risk of burning embers or sparks escaping the open chimney and falling on your roof or in your yard. An uncapped chimney will invite birds and animals to “nest” inside. This can block your chimney, and can result in a chimney fire.
Chimney caps come in many different styles and sizes. When deciding which style is best for you, first, know what kind of chimney you have. Also, dimensions are important to determine the cap size needed. You will need to know whether you have a single-clay liner, multi-clay liner, or no liner at all. Measure the top of the clay liner depending on what type you have and then decide the cap needed.
The five basic dimensions to measure a chimney cap:
- The first dimension is the length of both flues together.
- Second dimension is the width of both flues together.
- Third dimension is the width of the whole chimney crown.
- Fourth dimension is the length of the whole chimney crown.
- Fifth dimension is the height of the tallest flue. Allow 5 inches taller than the tallest flue for the screen altitude to keep the right draft.
Also when computing the mounting of your chimney caps, you may cover both the length and the width of the flues or you may cover the perimeter of the crown. Keep 2 to 3 inches of space for the mounting rims to attach to the crown. You will need the total dimension of the crown in the inside and outside measurement if you do not have clay flue tiles.