Chimney Cap Installation in New Jersey

Every open flue is better off with one, even though New Jersey's residential code does not require a rain cap on each chimney. The code sets the terms for a cap once it is installed. The value is practical: a cap stops rain from running down the flue, keeps wildlife out and holds back the leaves that would otherwise choke the draft of a boiler or water heater on the same stack.

That goes for flues nobody uses. A stack with one working boiler flue and one dead fireplace flue takes on rain through both, and the idle one has no heat to dry it. Water that gets in there soaks the masonry shared with the working flue. Covering the whole stack, or capping each flue on its own, keeps the unused side from damaging the side the house depends on. A brick or stone chimney built with a good crown still wants a cap, since the crown protects the masonry and only the cap protects the opening.

Stainless steel is the usual choice for most New Jersey houses, and copper is the other long-lasting option, while thin galvanized caps rust out soonest. A galvanized cap can look fine for a few years, then the mesh goes at the corners and the lid starts to shed flakes onto the crown. Black painted steel behaves the same way once the paint fails.

Salt changes the math. Within reach of the ocean and the bayshore, ordinary metal corrodes sooner than the same cap would in Bergen County, and the fasteners often go before the lid does, so a cap that looks whole can lift off in a nor'easter. On those houses the metal and the fasteners both get chosen with the salt in mind. On an oil-fired flue, the acidic residue in the exhaust is hard on thin metal too, and a screen sits in the flue gas every time the burner runs. What decides the life of a cap is how it is fastened and what it is made of.

A single-flue cap is sized to the outside of the flue tile, and a multi-flue cap is sized to the top of the stack so one lid covers every flue at once. Single caps clamp or fasten to the tile that stands above the crown. Where tiles sit at different heights, or a chimney has no tile showing at all, a multi-flue cap usually fits better, fastened to the crown or the brick.

The cap cannot choke the flue. New Jersey's residential code says the net free area under a rain cap, and through a spark arrestor screen, has to be at least four times the net free area of the flue outlet. A screen's openings cannot be larger than 1/2 inch, and the cap or screen has to be removable so the flue can be cleaned. That is why a cap is measured to the flue it serves and not picked by eye, and why a tight lid set low over a large flue can cause the same smoke problem it was bought to prevent.

An old cap has to go once the metal is rusted through, the mesh has torn or the fasteners no longer hold, because none of those failures can be patched for long. A cap that rattles in wind, sits crooked or leaves rust streaks down the crown is on its way out. Torn mesh is an open door for birds and squirrels, and a nest in a flue that shares a stack with a furnace can block the draft.

A screen packed with soot or creosote is a different case. The sweep can often brush it clean, but on a heavily used wood flue the mesh clogs again, and a fire that used to draw starts to smoke. If that keeps happening, a cap with a larger open area may suit the flue better. Where the fire has a real share of the heating, as with the stoves in Howell and Hopewell, the screen gets checked every time the flue is swept.

A cap keeps water out of the flue, not out of a cracked crown or lifted flashing, so a leak that continues after a new cap was fitted is coming from somewhere else. The evaluation looks at the crown and the flashing before the cap goes on, and if the crown is split, chimney crown repair belongs on the same scope. A cap also will not cure a flue that drafts badly because it is too short, too large or blocked lower down.

A factory-built fireplace is its own case: the metal chimney was tested with a matching top, so the replacement has to match the label on the unit. Every cap job begins with a free estimate. AMG is veteran owned, licensed and insured as NJ HIC 13VH13654300, and the line stays open 24 hours a day, 7 days a week, so a cap lost in a storm can go on the schedule before the next rain. When the flue has not been swept lately, chimney cleaning usually comes first, so the new cap closes over a clear flue.