What is a Single-Flue Cap? | TSE Glossary

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A single-flue cap is a stainless steel, galvanized, or copper hood that bolts to the top of a single flue tile, keeping rain, snow, debris, birds, and other animals out of the chimney while allowing combustion gases to exit. Most include a stainless mesh screen that doubles as a spark arrestor. NFPA 211 strongly recommends caps on every chimney and codifies minimum mesh-opening dimensions for spark arrestor function.

The cap consists of a flat or sloped top hood supported by sidewall posts attached to a base flange, which is anchored to the flue tile by tightening setscrews against the tile’s exterior. The mesh sidewalls keep birds, squirrels, and bats out while permitting full exhaust flow. Quality caps use stainless or copper hardware to resist corrosion, while builder-grade galvanized caps rust through within 10 to 15 years and must be replaced.

Single-flue caps work for chimneys with one flue tile per chase, the dominant configuration in DFW masonry construction. For chimneys with multiple flues serving different appliances, a multi-flue cap or chase cover with individual collars is required. Sweeps inspect cap condition during CSIA Level 1 visits, looking for damaged mesh, rust through, missing setscrews, and storm damage from hail or wind.

DFW chimney caps are heavily exposed to hailstorms, with the June 2025 events damaging tens of thousands of caps across the metroplex. TSE replaces hail-damaged single-flue caps with stainless or copper units featuring welded seams and reinforced mesh, sized to the existing flue tile dimensions. Quality caps deliver 25-plus years of service in DFW conditions when properly installed.

• [Multi-flue cap](/glossary/multi-flue-cap/)
• [Spark arrestor](/glossary/spark-arrestor/)
• [Custom copper cap](/glossary/custom-copper-cap/)
• [Bird guard](/glossary/bird-guard/)

• NFPA 211 (2024), Section 10.4.5
• IRC 2021, Section R1003.9.1
• CSIA Reference Manual

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