How it works

The technician inspects and cleans the flue, lowers a centered inflatable form, and pumps the cementitious slurry into the annular space between the form and the existing flue. The slurry fills cracks, voids, and missing tile sections, bonding to the masonry as it cures. After 24 to 48 hours, the form is deflated and removed, leaving a continuous interior bore typically smaller than the original tile but optimized for draft.

Cast-in-place liners shine when the original flue has lost integrity from a chimney fire, when the tile has shifted at multiple joints, or when the flue is oversized for the appliance it serves. The poured material reinforces the surrounding masonry and improves draft characteristics. Limitations include longer cure times, higher upfront cost than stainless reline, and non-removability if the appliance changes.

DFW context

DFW masonry chimneys with documented chimney-fire damage or extensive tile displacement are common candidates for cast-in-place lining, particularly in pre-1980 homes where the original clay tile has reached end of life. The method’s structural reinforcement is valuable on chimneys with foundation movement from Blackland Prairie clay shrink-swell. TSE specifies cast-in-place when stainless reline cannot adequately address structural integrity concerns.

Related terms

• [UL 1777 listed liner](/glossary/ul-1777-listed-liner/)
• [HeatShield](/glossary/heatshield/)
• [Flue tile](/glossary/flue-tile/)
• [CSIA Level 2 inspection">Level 2 inspection](/glossary/csia-level-2-inspection/)

Sources

• UL 1777 Standard for Chimney Liners
• NFPA 211 (2024), Section 10.6
• CSIA Reference Manual