Chimney caps and spark arrestors in Seattle

It sheds rain away from the flue opening, its mesh screen stops birds, squirrels and raccoons from treating an open flue as a nesting site, and where it doubles as a spark arrestor, it contains embers so they cannot drift onto a nearby roof. On a wood-shake or composition-shingle roof, which is most of what Seattle and King County are built with, that ember containment is not a decorative feature. It is the reason spark arrestors are written into fire code at all.

Where one is installed on a masonry chimney, the open area left by the mesh, once the wire itself is discounted, has to come to four times the flue opening or more; undersizing the mesh restricts draft and can push smoke back into the room. The mesh openings themselves have to fall between three-eighths and one-half inch: small enough to stop embers and animals, large enough not to clog with creosote and choke the draft. The screen material has to resist heat and corrosion to a standard equal to 19-gauge galvanized steel or 24-gauge stainless, and the whole assembly has to stay removable, since the code also requires that the flue underneath remain accessible for cleaning.

Fitting a universal or masonry-style cap onto a factory-built chimney can void that listing, and with it, in some cases, the coverage a homeowner’s insurance policy assumes is in place. We confirm which kind of system is on the roof before ordering a part, and for a factory-built chimney, that means sourcing the model the manufacturer actually lists for it.

Rain reaching an unprotected flue opening is what keeps a crown wet longer after every storm, which is a large part of what drives the cracking that eventually needs a full crown repair. Needles and moss collect faster on an exposed crown than a capped one. Birds and debris in an unprotected flue restrict draft and, in the worst cases, block it outright. A cap replacement is a small job next to a crown rebuild or a full repointing, and a large part of preventing either from becoming necessary sooner than it should.

A chimney that has never had a cap at all sometimes has an opening that is not a standard size, which we measure rather than assume. And a cap that failed early, corroded through in a few years instead of lasting decades, is often a sign the crown underneath is already letting water sit against the metal from below, worth mentioning before we fit the replacement rather than after.

Tell us whether your fireplace is a brick masonry chimney or a factory-built system in a metal chase, and whether you know the manufacturer if it is the latter. That lets us bring the right part on the first visit rather than a second trip. Most single-flue installations finish in under an hour. We work every day from 7 a.m. to 9 p.m. across a twenty-mile radius from central Seattle.