How thick must unlined masonry chimneys be?

Unlined masonry chimneys must be at least 8 inches thick to meet safety and structural requirements defined in building codes. This thickness is essential to ensure the chimney can withstand the high temperatures produced by the flue gases and adequately contain any condensation that may occur, thus preventing structural damage and increasing fire safety. The thickness also helps provide sufficient insulation and stability to the structure over time, reducing the risk of deterioration from environmental factors. In contrast, thinner options such as 4, 6, or even 10 inches would not provide the necessary protection and structural integrity needed for safe chimney construction.