Independence · Wasatch County
Capping an Open Flue in Independence
An uncapped chimney on the edge of open country is a warm, dry, sheltered vertical cavity in a landscape that does not offer many. Something will find it.
What moves in
Birds are the most common, and they build in spring, high in the flue where the shaft narrows. The nest is dry twig and grass sitting directly above where you intend to light a fire, and it is also a blockage that pushes smoke and carbon monoxide back into the house. Squirrels get in and often cannot get out, because glazed tile gives nothing to climb. Bats will use a flue as a roost. Wasps build in the sheltered top of a stack over a summer.
All of it is prevented permanently by a stainless mesh cap, which is one of the least expensive things anyone will ever fit to a chimney.
We will not seal something in
Worth saying plainly, because we get asked. If there is an active nest or an animal in your flue, we remove or exclude before capping. Sealing a living animal into a chimney is inhumane, it produces a far worse problem when it dies in there, and some species and nesting seasons carry legal protection. Occasionally the right answer is that the cap waits a few weeks. We will tell you when that is the case rather than doing the quick thing.
Screen mesh, and getting it right
A cap screen is doing two jobs at once and they pull in opposite directions. Fine enough to stop embers leaving and animals entering, open enough that soot and moisture do not blind it. Too fine a mesh on a wood-burning appliance clogs within a season, and a clogged screen is a blocked chimney. Sizing it correctly for what you burn is the difference between a cap that works for twenty years and one that causes a callout every fall.
Snow, ice and the crown
Meltwater running off a cap refreezes on cold metal, and a cap can ice over enough to restrict the flue during a thaw and refreeze cycle. Height and lid clearance matter for that reason. Underneath it, the crown is the surface actually protecting the masonry, and a cracked crown lets water into the top of the stack where it will freeze and open the joints. A cap over a failed crown is a lid on a leaking box.
Not every chimney around Independence is masonry, either. A good share of the houses here are recent builds and cabins with a factory-built metal fireplace inside a framed and sided chase, and on those the crown's job is done by a sheet-metal chase cover. Covers made flat pond water rather than shedding it, rust through at the low point, and then drain into the chase around the flue pipe where nobody sees it happening. If your chimney is a sided box with a metal top rather than brick, that cover is the first piece to look at.
Top-sealing dampers
Where a chimney is used occasionally, a damper at the crown with a gasket seals better than a cast plate at the throat, keeps the whole shaft dry, and stops the steady loss of heated air up an unused flue across a long heating season.
Questions
Caps & Dampers in Independence — common questions
There is something living in our chimney. Can you just cap it?
Not until whatever is in there is out. Capping over an animal is cruel, creates a worse problem, and in the case of some nesting birds there are protections on timing. We clear and clean first, then cap so it cannot recur next spring.
Will a cap stop the smell of smoke coming down the chimney in summer?
It helps, because it keeps rain off the deposits that produce the smell, but the more effective answer is a top-sealing damper that closes the flue at the crown. A thorough sweep to remove the source is usually part of it as well.
Our cap keeps clogging with soot. Is that normal?
It means the mesh is too fine for what you burn, or the fire is running cooler and dirtier than it should. Both are fixable. A cap should not need clearing every season, and a blinded screen is effectively a blocked chimney, so it is worth sorting out.
Should the crown be repaired at the same time as fitting a cap?
If it is cracked, yes. The cap keeps the weather out of the flue opening, and the crown keeps it out of the masonry itself. Fitting a cap above a failed crown leaves water entering the top of the stack, which is where freeze damage does the most harm.
Also in Independence
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Chimney Sweep Inspection Chimney Repair Fireplace Repair Installation Gas Fireplace Dryer Vents All Independence services
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