Local chimney cap replacement for Fernandina Beach homes

How a galvanized cap runs out of zinc

A galvanized cap is steel protected by a zinc layer that corrodes in the steel's place. The zinc wears away fastest where water lingers: along the screen wires, at folded seams, and around fastener holes.

Once it is gone in a spot, the steel beneath rusts, and rust takes up more room than the steel it came from, so the wires swell and break. Streaks of orange on the crown or the brick below are the visible sign of that stage. By then recoating is not practical, since the zinc cannot be put back on the roof, and the cap is replaced in a longer-lived metal with the old fasteners removed as well.

A damper that doubles as the rain cap

Fitted to the flue tile in place of a cap, a top-sealing damper has a hinged lid with a gasket and is opened and closed by a stainless cable that runs down to a bracket inside the firebox. Closed, it seals the flue at the top, which keeps conditioned air in the house and rain out of the flue. Models with a screen in the frame also keep animals out, as a cap would. It is chosen when the throat damper is rusted or warped, and it follows its maker's sizing just as a cap does. The one thing to remember is to open it fully before any fire is lit.

Cap metal where salt reaches the roof

Salt carried on the wind settles on a cap and draws moisture to it, and chloride salt attacks metal that would last for years further inland. Some cap makers offer a Type 316 stainless line, sold as marine grade, for sites near salt water, since the molybdenum alloyed into 316 resists chloride pitting better than the common grade. A stainless-steel guide from the International Molybdenum Association adds that sheltered, rain-shadowed crevices hold salt longer than surfaces rain rinses, and a cap screen is full of such crevices. We follow the maker's grade guidance for the exposure, name the grade, and suggest rinsing the cap when the chimney is serviced.