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Originally published in the September 2016 issue of Sweeping Magazine


Question: I recently swept a wood burning masonry fireplace and observed that mortar is missing from the joints between clay tile liner sections in multiple areas. Should I recommend joint repair, or a reline with a stainless steel liner?


by Mike Segerstrom 


That depends. As chimney service professionals, in addition to sweeping and inspecting chimneys, we should understand available repair options and methods. Even if our company does not perform these services, having a thorough understanding demonstrates our professionalism and provides a better service to our clients.

Looking at the question, there is much to consider when making a recommendation in this situation. The first step in making any accurate repair recommendation, is inspection of the chimney. Did we do level 2 inspection, or at least perform an internal camera inspection of the clay flue liner? Even if we have scanned the flue, it is prudent to perform a level 2 Inspection when defects in a liner are present. This will help us determine if other components of the system are also in need of repair or corrective action. Often times completing a level 2 inspection will give us information that has a direct impact on our liner repair/replacement recommendations.

If we are considering relining, the NFPA 211 specifies that a level 2 inspection shall be performed "prior to relining or replacement of flue lining". It also states that a level 2 inspection should be performed when "level 1 inspection is insufficient to determine the suitability of continued use of the chimney." Completing a level 2 inspection will help us confirm If joint repair is an option, as joint repair products will have specific chimney requirements.

Take for example, chimney exterior airspace clearance to combustibles requirements. We know that an exterior chimney has a 1” requirement, where an interior chimney has a 2” air space clearance requirement. The installation or application instructions of the joint repair products available to us require that chimney air space clearances to combustibles are maintained. In other words, these products do not reduce chimney clearance requirements. A UL Listed insulated stainless steel liner (and other UL Listed relining products and systems) will reduce chimney exterior clearance requirements to 0 inches.

So if we have performed a level 2 inspection, there's a good probability that we will have been able to confirm if chimney clearances are present. If they are not, then we have to recommend a repair method (relining) that reduces these requirements to 0 inches. If chimney clearances are maintained, then a joint repair could be a viable option.

Not technical, but often very important, is the cost difference between a joint repair product or a full stainless steel reline.  Relining a fireplace with a stainless steel liner can be a costly project. Joint repair can be a more cost-effective alternative. If the chimney is suitable for either method, the client should be educated on the benefits of both, including cost aspects.

Product warranties can also play a role in our client's decision. Over the last 10 years or so, most of the stainless steel liner manufacturers are now offering limited lifetime warranties.  These warranties may even be transferable if the client sells the home. These warranties typically cover use with multiple appliance types and fuels, including an open hearth wood burning masonry fireplace. Clay liner joint repair product warranties are similar, with some differences. As an example, one joint repair product has a limited lifetime warranty, but this warranty only covers the product when it's installed in a chimney that is connected to Listed Appliances. Since our chimney in question is a masonry fireplace and not a Listed Appliance, this product may work well, but there would be no warranty if it were installed. In addition to having a working knowledge of repair options, we should also know the warranty information.

Back to the technical side of things. Let's say that the fireplace chimney we are discussing does meet clearances. Since we are talking about voids in the liner, we have to pay special attention to inspection of those voids. Specifically, are they clean voids, or are they full of soot and creosote? If we see soot and creosote in these voids, there is a significant likelihood that soot and creosote have traveled into the structure between the clay tile and masonry of the chimney. If the voids are large enough, we may actually see it. These deposits may be in the form of creosote carried out by condensation leaks at the joint, or smoke entering this area.

A mortar joint repair does not address these deposits. Creosote is combustible, and may be exposed to excessive heat and ignite. A stainless steel reline would also not address these deposits, unless the clay liner was removed. Clay liner removal would provide access to the chimney structure interior, and allow for removal of soot and creosote in these areas. So even if the existing clay liner would accommodate a properly sized and insulated stainless steel liner, it would still be necessary to remove the clay liner if evidence at the mortar joint voids indicates that creosote is present outside the clay liner.

There is often more to repairing or restoring a fireplace system than just addressing the liner. Level 2 inspection will help identify additional issues. The focus here is on options for liner joint repair or replacement, and a few of the important aspects we need to consider when making a repair recommendation.

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