the more you know

Creosote Removed FROM FLUE

Expanded Creosote removed from a wood burning fireplace during a typical inspection. This type of buildup is known as “expanded creosote”. Creosote, once ignited, expands into a mass. This is evidence of a flue fire. A flue fire cannot only damage the existing chimney liner but also exposes the wood structure against the chimney to intense heat. Build up like this comes from either green wood, wet wood, burning the wrong type of wood or a lack of maintenance.

Gap between Flue Tiles in Masonry Chimney

View looking down a wood burning fireplace flue during a typical inspection. The clay tiles are not only misaligned but have large gaps between the tiles. This can be caused by settling, but the more common cause is original construction defect. The gap between tiles was too large and the wrong mortar was used. Expansion and contraction of the flue tile when heated and cooled causes the mortar to fall out, leaving an even larger gap. Chimney liners (whether stainless steel or clay tile) must be free of gaps, voids and cracks. Voids, gaps and cracks can allow flue gas to escape the system. Flue gases contain all the byproducts of combustion. Once these escape the chimney lining, they become unpredictable and can potentially be release into the living area.