Chimney cap replacement in Nassau Village-Ratliff by local cap pros

The half-inch and three-eighths rule for screen openings

Florida's residential code sets the screen opening size on a masonry chimney spark arrestor with two spheres. An opening may not let a sphere larger than 1/2 inch pass, which holds back embers large enough to start a roof fire. It also may not block a sphere smaller than 3/8 inch, which keeps the mesh open enough for the chimney to breathe. Screens outside that window fail in opposite ways: too coarse lets embers out, too fine clogs with soot and slows the draft. Any cap we propose has its mesh checked against both limits, and caps sold for other uses, such as gas vents or roof vents, may not meet them.

Rain that slips past a cap

A cap sheds rain that falls straight down, but wind-driven rain can travel sideways under a shallow hood and into the tile. Some cap makers offer deeper hoods or models with side baffles for chimneys that stand exposed, and their literature says which.

Before we recommend a deeper hood, we confirm the water really arrives through the flue opening. Rain soaking through the crown or the brick shows up in the same firebox, and a larger hood does nothing about it. So the answer names the path we found, what closes it, and whether a bigger cap belongs in it at all.

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.