Local chimney cap replacement for Crawford 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.

Why a screen needs four times the flue's open area

Beyond the opening size, the code sets how much total open space the screen must have. After the wire and frame are subtracted, the screen's clear area has to reach at least four times the clear area of the flue outlet under it. Wire takes up part of every square inch of mesh, so the screen's overall size must be well beyond the flue opening to leave that much air path. The rule explains why a cap for a large flue is noticeably taller or wider than one for a small flue. A cap that looks generous from the yard can still fall short once the wire is counted, which is why we size from the maker's data rather than from appearance.

A flue tile cut level with the crown

Some crowns were poured up to the top of the flue tile, or the tile was cut off level with the concrete. Most single-flue caps need tile standing above the crown to clamp around or seat on, so a flush tile leaves them little to hold. The practical answers are an outside-mount cap that fastens to the crown itself, or a crown repair that re-forms the top with the tile standing proud and a caulked joint around it. We explain both, since the second also corrects a crown detail the chimney design note from BIA treats as standard: the tile standing at least 2 inches above the crown.