Common Fireplace Installation Errors

Common Fireplace Installation Errors

While improper design and lack of maintenance are often the causes of fires, an often-overlooked cause is improper installation, including common errors such as:

• Framing – Combustible materials can catch fire if they are placed too close to the fireplace, which violates both building codes and manufacturers’ installation requirements. The protection of adjacent combustible material must allow for the fact that wood and other combustible materials suffer from decreased resistance to ignition after exposure to continual heating at even moderate temperatures. When wood is exposed to heat over a period of time, it undergoes a gradual change in its molecular structure through a process called pyrolysis. The complex organic molecules of which wood is composed are slowly broken apart, and much of the original weight and structural integrity of the wood is lost. As this process continues, the material left behind is charcoal, which is also known by the more ominous sounding and technically correct term pyrophoric carbon. Pyrophoric carbon is different from wood and has different properties. It has a significantly lower ignition temperature than that of the original wood. Various studies have fixed this temperature at 200 to 250 degrees Fahrenheit. Concealed areas such as floor/ceiling assemblies and wall penetrations are particularly vulnerable, and the on-off pattern of heating from chimneys probably contributes to the problem. Wood exposed under these circumstances is converted to pyrophoric carbon and is "primed and ready" to burn. Often an unusual incident such as accidental overfiring provides the occasion for ignition. The temperature produced by the chimney need not become extremely high. A rise into the 200 degrees F range, together with the self-heating properties of the carbon, may be sufficient to initiate the combustion process.

• Mantel – If installed too low or too close to the top of the firebox, the mantel can catch fire.

• Finish materials – Combustible materials are often used in areas that require non-combustibles. The paper facing on drywall, for instance, can be a combustible material.

• Gas line entry – The gas line entry must be properly sealed with a high-temperature sealant.

• Flues – The flue must be adequately sized; if offset, the flue’s size is reduced.

• Gas log sets – If gas logs are too large or installed too forward, this can pose both a fire and burn hazard.

• Chimney shrouds – When using metal shrouds, they cannot be constructed around the termination cap unless authorized by the manufacturer.

• Cellulose Insulation - Blown cellulose insulation products should never be installed in direct contact with any combustion appliance chimney, vent or flue pipe, nor against or over any non-IC (Insulated Contact) rated recessed light housings or fixtures. Most fire codes mandate a minimum two-inch space between combustible materials and masonry chimneys, some types of triple-wall vent pipe. For single-wall vent pipe, these minimum clearances to combustible materials increase substantially to eighteen inches. For double-wall vents, these clearances are typically reduced to nine inches for ‘Type L’ oil and solid fuel vent, and six inches for gas ‘B Vent’.