Expert: James Ball - 12/21/2011

Question
I have a 4' tall by 8' wide by 4' deep firebox with an 18' dual flue chimney plan. However, the plan does not give me the "Draw" design or requirements for build or design build. Thank you for your attention.

Answer
IHello George, there are different requirements in different areas of the country, your building department should have the formulas you need, if not s local mason should have that info it is based on the flue size, "a round shall have a minimum net cross-sectional area of at least one twelfth the fireplace opening" NFPA,211.
Happy Holidays
James