Herriman · Salt Lake County
Spark Arrestors and Caps in Herriman
On the western edge of the valley, where the subdivisions run up to dry open ground below the Oquirrhs, the mesh in a chimney cap is doing a job that has nothing to do with keeping rain out.
The mesh is a spark arrestor
A wood fire lifts embers. Most burn out inside the flue, but a hot fire in a strong draft can carry live material out of the top of the chimney still glowing. That is why a cap has a screen: the mesh catches embers and holds them until they die. In a built-out neighborhood with irrigated lawns on every side, an ember landing on the ground is a non-event. On the edge of Herriman, where dry grass and brush run right up to the back fence and stay dry from June onward, it is not something to be relaxed about.
The practical points are simple. The mesh has to be intact, which means checking it rather than assuming it, since screens corrode and get damaged by cleaning. The mesh size has to be right, coarse enough not to clog with soot and fine enough to hold embers. And it has to be fastened, because a cap that has lifted in the wind is arresting nothing.
Wind off the canyons
Air moving out of the Oquirrh canyons and across the open bench works on hardware. We routinely find caps here missing fasteners, or held by screws driven into thin metal that has since torn. Stainless hardware, enough fixing points, and a check every time the chimney is swept is the whole maintenance regime, and it is not much to ask of a component that protects everything below it.
Water, and the dampers most of these houses do not have
An open flue takes every storm straight into the smoke shelf and the damper, where the water sits and rusts things in place. A cap stops that, which is the reason a cap pays for itself even where embers and animals are not a concern.
On dampers, know which system you have. Factory-built fireplaces, which is most of what is installed in Herriman, have no throat damper at all; they are sealed by design and there is nothing to open or close. Masonry fireplaces do have one, and where the original plate no longer seals, a top-mounted damper with a gasket closes the flue at the roofline and stops the house losing heated air up the chimney around the clock. Where masonry is exposed, a vapor-permeable water repellent is the finishing step, and it has to be the breathable kind. A sealed surface traps moisture in the brick and the next hard freeze uses it.
Questions
Caps & Dampers in Herriman — common questions
How do I know if the spark arrestor screen is still intact?
It needs looking at, since a corroded or damaged screen is not visible from the ground. We photograph the cap on every sweep. If you burn wood and live near open ground, it is worth confirming rather than assuming.
Our cap has no mesh, just a lid. Is that acceptable?
A lid keeps rain out and does nothing about embers or animals. On a wood-burning chimney anywhere near dry vegetation, a screened cap is the sensible specification, and on many installations a spark arrestor is required rather than optional.
Do gas fireplaces need a cap on the vent?
Direct-vent gas appliances come with a manufacturer's termination that serves that purpose and should not be modified or covered. What they do need is clear space around them, since anything that obstructs the terminal affects both the exhaust and the combustion air.
Is chimney waterproofing worth doing on newer masonry?
On exposed masonry, yes, provided the product is vapor-permeable. It slows the freeze-thaw damage that gets into the joints. What it must not be is a film-forming sealer, which traps water inside the brick and makes the damage worse rather than better.
Also in Herriman
Our other services here
Chimney Sweep Inspection Chimney Repair Fireplace Repair Installation Gas Fireplace Dryer Vents All Herriman services
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