We recently replaced an ancient chimney-vented boiler with a direct-vented one. This boiler was the only thing using our chimney. The chimney is brick and sits in the center of our 120-year-old house. On top, it has an old, rusted rain cap (now closer to a funnel than a cap).

The heating contractor sealed the old exhaust opening in the basement using a metal plug and concrete patching compound. (There is also a cleanout in good condition in the basement.)

What's the right thing to do to seal or cover the top? Masonry cap, cover with sheet metal, regular chimney cap, or something else?

  • Update: we simply ignored this unused chimney for about a year. Then we decided to remove it completely. I hired roofers to remove the portion above the roof line and patch the roof. Then I removed it in the attic, two floor of living area, and basement. Lots of heavy lifting, but it enabled an improved layout of our kitchen/dining room! Aug 11, 2015 at 18:42

1 Answer 1


The answer is going to depend on whether or not you intend to ever use this flue again. If it is never going to be used, I'd seal it up with a solid cap, mortared down. if you think you may need it again, then a simple rain cap with a vermin screen would be fine.

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