sweep on roof inspecting chimney

Have A Damaged Masonry Liner? HeatShield® May Be Able To Help

HeatShield Joint Repair Diagram

A crack in a masonry chimney liner can be a pretty big deal, but with the price tag of a new liner, you may think it’s overkill to reline the whole flue. Well, if we’ve just described your situation, we have good news for you. Depending on the size of your flue in relation to your firebox, we may be able to repair your cracked liner with HeatShield®, so you can enjoy your home heating system without installing a whole new liner.

HeatShield® is a cerfractory sealant that was developed over 20 years ago, specifically for flue liner repair. The sealant is able to withstand the moisture and corrosive flue gases produced by the fire, and temperatures in excess of 2900 degrees F. HeatShield® is also approved for all fuels, has passed extensive testing, and surpasses the mortar requirements of both the National Fire Protection Association (NFPA) and the International Residential Code (IRC). It’s an eco-friendly product created from naturally occurring and recycled materials, and it carries a 20-year material warranty.

Not just anyone can become a HeatShield® certified installer — you must be chosen based on your experience and industry certifications, and train in the HeatShield® factory. But as HeatShield® certified installers, you can expect us to do the job right.

There are a couple of different applications for different situations — here’s how each works:

  • Joint Repair — The joints that rest between the clay tiles of a masonry chimney liner can really take a beating over time. The heat of the fire and the corrosive byproducts and creosote produced by the fire can eat away at these joints, and cause cracking, holes, and gaps, which negatively impacts the safety and efficiency of the chimney. But with the HeatShield® joint repair system, we can restore these damaged joints, missing joints, or gaps in the liner. We simply apply the cerfractory sealant to the damaged joints and use a foam applicator (which is custom-fitted for your chimney) to press and smooth the product in and over the holes, cracks, gaps, and voids. When we’re finished, the flue is smoother, stronger, and smoke-tight, so you can enjoy your heating system again. 
  • Flue Resurfacing — Damage isn’t always isolated to a few mortar joints here and there — sometimes the clay tiles themselves crack or spall, and the surface of the entire flue is worn, deteriorating, or otherwise not conducive to proper draft and a safe fireside experience. When the damage is more widespread and damage can be found all along the flue liner, as long as the structure itself is still sound, we may be able to completely resurface the liner using the HeatShield® flue resurfacing system. The system involves the application of a prep or tie coat, which is applied using a custom-fitted foam applicator. Once the prep coat dries, we pour the HeatShield® cerfractory sealant down into the flue, and use the foam applicator to ensure the coat is evenly spread out and smooth, and that all gaps, cracks, voids, and holes are filled. What you’re left with is a stronger flue and a smooth, smoke-tight surface.

No matter which HeatShield® application we use, we’ll perform a video scan and provide you with both a before and after view of your chimney flue, so you can see the difference.

Are you interested in learning more about HeatShield® and whether or not it’s right for your flue repairs? Give us a call at 610-626-2439 or fill out our online appointment request form — we’d love to talk more about it and help you decide if HeatShield® is right for you.


Stainless steel liners are another flue relining option that you can discuss with our expert technicians.