Chimneys and fireplaces continue to be built with design and construction flaws. These flaws occur in small fireplaces and sophisticated ones, in rural and urban areas, in all parts of the country. Ten of the most common problems are described here. 1. INADEQUATE CLEARANCE FROM COMBUSTIBLES Inadequate clearances are common at the header supporting the stud wall above the fireplace opening. 2. INADEQUATE WALL THICKNESS Firebox and smoke chamber walls commonly don't have full lining or thickness. BIA requires the firebox wall to be at least 8 inches thick. 3. POOR LINER JOINTS Flue liner joints are frequently incompletely filled. 4. HOLLOW OR MORTAR-FILLED FIREBACKS The space behind the fireback is often improperly left empty or packed with rubble and mortar. 5. SEPARATED FIREPLACE FACE 6. IMPROPERLY SUPPORTED INNER AND OUTER HEARTHS 7. POOR SMOKE CHAMBER CONSTRUCTION Many smoke chambers are poorly proportioned and actually inhibit the flow of gases. 8. IMPROPER CLEARANCE BETWEEN FLUE AND CHIMNEY 9. IMPROPER CROWN CONSTRUCTION Most observed crowns are composed of a thin mortar wash that deteriorates rapidly. 10. CHIMNEYS TOO SHORT OR TOO TALL