https://www.homebuildingandrepairs.co... Visit our website to learn more about masonry, home building and construction repairs. In this video I will provide you with a few different methods you can use to calculate or figure out the height of a fireplace chimney built over a roof.

Here's a reference for similar building code.

R1003.9 Termination. Chimneys shall extend at least 2 feet (610 mm) higher than any portion of a building within 10 feet (3048 mm), but shall not be less than 3 feet (914 mm) above the highest point where the chimney passes through the roof.