Historically, the only available method to repair defective or deteriorated mortar joints between flue liners in a masonry chimney was to reline the flue. Using the FireGuard ceramic sealant, the need to reline the chimney is negated, saving time and expense.


The Problem

During original construction, it is not uncommon for masons to improperly align the flue liners or neglect to fill the joints between the flue liners with the appropriate refractory mortar. As stated in The BOCA National Mechanical Code, M-1207.2.1 Fire-Clay flue liner:  The fire-clay flue liner shall be installed ahead of construction of the chimney as the chimney is carried up and carefully bedded one on the other in an approved medium-duty refractory mortar, with close joints left smooth on the inside. Even if the mason filled the joint with mortar, it most likely was the same mortar used to lay the brick, block or stone, which is not an approved refractory. In fact, standard mortar has almost no refractory properties. Standard mortar in the joints of flue liners cannot withstand the adverse conditions present within a chimney environment. The result of using standard mortar is rapid deterioration of the joint, ultimately leaving dangerous openings between the flue liners.

The Danger of the Problem

The results of these improper practices are dangerous openings within the flue area. These openings allow flammable creosote (by-products from wood combustion) to build-up between the outside of the flue lining and the inside of the chimney casing. Should these flammable deposits ignite, the heat and quite possibly the flame could transmit to the dwelling. As recommended by the National Fire Protection Agency 211 – Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances,  If the flue liner in a chimney has softened, cracked or otherwise deteriorated so that it no longer has the continued ability to contain the products of combustion (i.e., heat, moisture, creosote, and flue gases), it shall be either removed and replaced, repaired, or relined.  In the past, relining was the only option . Now, you and your chimney professional have a viable, safe alternative – FireGuard ceramic sealant; it is the most cost effective product addressing dangerous gaps between flue.

The Solution

The FireGuard ceramic sealant is a high-duty, refractory mortar specifically designed to correct open mortar joints, thus negating the need to reline the flue. The 3,200 degree service temperature far exceeds the requirements for residential chimneys. Applied by chimney professionals, the unique FireGuard material forms solid, smooth, water and acid resistant joints throughout the entire flue area. Once properly installed, the new FireGuard joints prevent the passage of flammable creosote through the joints, thus preventing the build-up of flammable creosote outside the flue area. In addition, the new FireGuard joints reduce heat transfer through the joints to the interior wall against the dwelling. Under normal operation of a masonry chimney, FireGuard is guaranteed not to loosen or dislodge from the joint(s) for a period of twenty years (please see your chimney professional for details).

Closed-Cell applicator with vibrator

Closed-Cell applicator being installed through clean-out door opening

Preparing to mix FireGuard material

Winch with cable to applicator

Winch with cable to applicator

Fireguard as it approaches a deteriorated mortar joint

View of FireGuard on the exterior of a flue liner as the as the FireGuard seeps through the joint

Heater setting the ceramic compounds in FireGuard

Completed FireGuard installation

Why FireGuard?:

The FireGuard process costs substantially less than traditional relining; in some instances as much as 50% less.

The FireGuard process is in full compliance with standard building codes. In fact, the FireGuard material far exceeds the service temperature requirements for residential applications.

The majority of the FireGuard process is usually completed within a single day, with much less disturbance to the inside of the home since the flue liners do not require removal.

The FireGuard process does not appreciably decrease the area of the original flue; therefore, the performance of the fireplace or appliance should not change.

The FireGuard material improves the durability of the vitreous clay flue liners comprising your flue.

The FireGuard material is guaranteed for twenty years not to fail (please see your chimney professional for details).

The FireGuard process was developed by Firesafe Industries, a company special- izing in chimney restoration products and processes for over 45 years.

For whatever service need, The Atlanta Chimney Doctor will send out a technician to fully appraise the situation. Please call our office at (770) 429-8320 to schedule your appointment.

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