How to Design Custom Chimney Caps that Work

by DoItYourself Staff

what you'll need

Drawing board and pencils
Tape measure marked in centimeters
Notebook or tape recorder

Well-designed and fitted custom chimney caps will keep debris, birds and animals from getting into your chimney. Precise measurement and simple design will create a chimney cap that enhances the safety of your home and family.

Step 1: Measure Your Chimney Flue Top

Measure the length and width of the mortar crown of your chimney, where it narrows just below the flues. Add 1 inch to this dimension for the base size of the chimney cap. If you have more than 1 chimney flue, design a cap to surround all of them, allowing a more exact fit. Add 1½ inches to the base length and width for a mounting flange. This will be bolted into the mortar crown.

Step 2: Measure the Height of the Flue Tops

Measure to the top of all the flues. The chimney cap must be at least 4 inches higher than the tallest flue top for adequate ventilation of the chimney when capped.