Local chimney cap replacement for Murray Hill homes

Slip-in caps and the inside of the tile

A slip-in cap has a lower section that drops inside the flue tile and holds with screws or spring clips against the tile wall. It suits a tile with a clean, square top edge and inside dimensions that match a standard size. The fit is measured right at the top of the tile, where old mortar, chips or a rough cut can make the opening smaller than the tile's nominal size.

A slip-in section forced into a tight tile can crack it, and one that sits loose will rattle and walk. When the inside of the tile does not measure true in both directions, a band-mount or outside-mount cap is the better choice, and we explain which and why.

A flue serving a furnace or water heater

When a masonry flue carries exhaust from a heating appliance or water heater, that appliance's installation instructions govern the vent, including what may sit on top of it. Those instructions can call for a particular cap type or rule out a fine screen, because mesh on an appliance flue can collect debris and restrict the exhaust. We identify the appliance on each flue before choosing a cap, follow its instructions, and record which cap went on which flue. If the appliance vents through its own metal pipe running inside the chimney, that pipe stays with the termination its own maker specifies, and we leave it as it is.

Clearing nest material before capping

Putting a cap on over an old nest traps the problem inside. Twigs, leaves and droppings on the smoke shelf block the draft and can catch fire from the first ember that reaches them. So the flue is cleared from the top and the shelf is cleaned from below before a new cap goes on.

If an animal is still inside, it has to come out first, and that is a separate job, priced on its own. The room below is covered while the debris comes down. The cap is the final step, the one that keeps the cleared flue clear, and it goes on as soon as the clearing is finished, the same day when the cap is already on hand.