Choosing Caps and Chase Covers for Hideout

Staying attached

The most common cap failure we are called out to on exposed ground is not corrosion. It is departure. Caps that friction-fit over a flue tile, or that are held on with two short screws into thin metal, come off. On a ridge with little to break the wind, that happens sooner than the installer expected, and until somebody notices, the flue is standing open to the weather. Caps here need to be mechanically fastened, into sound material, with stainless fixings that will not seize or corrode into the fitting they were meant to allow removal from.

Chase covers earn their specification

On a framed chase, the cover is doing the work a masonry crown does and it is made of sheet metal, which means the specification is the whole story. Sloped rather than flat, so meltwater leaves. A cross break down the middle, so a wide pan cannot pond in the center. An overhanging drip edge so water leaves the assembly rather than running back down the siding. A collar around the pipe that is mechanically formed and sealed, not just caulked. Stainless where the exposure is real. A flat galvanized pan rusts through in a few winters and the damage happens inside the chase where nobody sees it.

Spark arrestors and dry ground

Summers here are dry and the vegetation on this kind of open, sagebrush and scrub ground carries fire readily. A spark arrestor is the screen in a chimney cap, and its function is to stop an ember leaving the flue and landing on that. It matters most for wood-burning appliances and for anyone with a fire pit or an outdoor fireplace. The screen has to be the right mesh: too coarse and it stops nothing, too fine and it blinds with soot and chokes the draft.

Snow and the termination

Direct-vent terminations have their own caps, and those need to be the appliance manufacturer's approved component. It is worth choosing the wind-resistant version at the outset on an exposed elevation rather than after the first winter of nuisance pilot outages.

Sealing veneer and exposed masonry

Where a chase is faced in stone, the veneer and its joints will absorb water. A breathable siloxane sealer reduces that. A glossy film-forming product traps moisture behind the face and makes freeze damage worse, so it is worth checking what is being applied before anyone starts spraying.