Flue Liner Repair, Replacement, and HeatShield Options

Why the liner matters

The liner contains combustion gases, protects the masonry from heat and acidic byproducts, and helps the chimney draft. Cracks, missing pieces, or open joints can let gases and heat reach the masonry or the house. Assessment usually starts with an inspection and often a camera scan. See camera inspections.

The main options

• Repair in place: sealing localized joint gaps or cracks where the damage is limited.
• Resurfacing: coating the interior of an existing tile-lined flue where the structure is otherwise sound.
• New liner: installing a stainless steel liner or a cast-in-place liner. See chimney liners.
• Removal and relining: more extensive work where the damage is severe.

What HeatShield is

Per the manufacturer’s product label, HeatShield Cerfractory is a flue sealant made by SaverSystems. Used on its own, it is intended to repair and restore an existing, structurally sound masonry chimney so it can keep containing and conveying the products of combustion. It is not a liner by itself. Manufacturer materials describe three approaches:

• Joint repair, for defective mortar joints between flue tiles
• Resurfacing, for mortar joints and minor tile defects in tile-lined flues with limited damage
• CeCure sleeve relining, for serious defects or unlined chimneys, where a ceramic-insulated sleeve reinforced with stainless steel fabric is installed between coats of HeatShield. The manufacturer states that this sleeve system functions as a chimney liner and is listed to UL 1777 for residential chimneys serving Category I gas, oil, and solid-fuel appliances.

The manufacturer also says the product must be installed by trained personnel. Whether a particular flue is a candidate depends on its condition, which is why the flue is examined before a method is chosen.

Material and appliance compatibility

Whatever liner or repair method is used, it has to suit the fuel and appliance. Wood, gas, and oil appliances produce different gases and temperatures, and a change of appliance or fuel can mean an existing liner is no longer suitable. Ask for the manufacturer’s documentation for any product proposed. Do not change venting or an appliance yourself.

Repair or replacement: decision factors

• The extent and location of the damage
• Whether the flue is sized correctly for its appliance
• The condition of the masonry around it
• Whether the flue is tile-lined, and whether the tiles are intact enough to repair
• Cost, disruption, and expected longevity as described in the product’s documentation

Questions to ask

• What is the defect, and how was it found?
• Is this flue a candidate for repair, or does it need a new liner?
• Which product is proposed, and what are the manufacturer’s conditions for it?
• How will the finished work be checked?

Related projects and pages

Our chimney flue repair and chimney liner pages describe our work. See project write-ups in Plainsboro, Hillsborough Township, and Jersey City, or browse Our Work.

Source: HeatShield Cerfractory product label, SaverSystems.