Sandy · Salt Lake County
Caps, Dampers and Keeping Weather Out of a Sandy Flue
An uncapped chimney is a hole in your roof about the size of a dinner plate, pointing straight up, on the highest part of the house. On the Sandy bench it also happens to sit in the path of air coming downhill off the mountains.
What the cap is actually doing up there
Four jobs, and the small ones matter as much as the obvious one. It keeps rain and snow out of the flue, where water dissolves mortar joints from the inside and rusts a steel damper into place. It keeps birds and rodents out, and a nest built partway down a flue is a complete blockage that people usually discover by filling the room with smoke. It stops embers landing on the roof. And a correctly built cap with the right overhang stabilizes the draft when air is moving across the top of the chimney, which on the east side of Sandy is most winter evenings.
That last point is worth dwelling on, because it is the one homeowners never expect. When downhill air off the canyons crosses a chimney top at an angle, the pressure at the flue opening changes, and a fireplace that drafts fine in still weather starts pushing smoke back into the room. A properly shaped cap converts some of that crossing air into lift rather than turbulence. Where a standard cap is not enough there are wind-directional designs that rotate to shield the flue from whichever side the air is coming from. That is a specific, physical fix for a specific, physical problem, and it is far cheaper than the masonry work people sometimes get sold for the same symptom.
Dampers, waterproofing, and the order to do things in
Most older Sandy fireplaces have a throat damper, a cast plate at the bottom of the flue. They warp, they rust, and they never sealed well to begin with, which is why an unused fireplace can feel like a draft in the room all summer. A top-sealing damper mounts at the crown with a rubber gasket and closes the flue properly, so it also keeps out the water and animals a bad cap was letting through.
Waterproofing comes last, not first. There is no point applying a repellent to brick while the crown is cracked and the cap is missing, because the water is entering from above and no amount of surface treatment stops that. We seal the crown, fit or replace the cap, then treat the masonry with a vapor-permeable repellent that still allows the brick to dry outward. Done in that order it lasts. Done in the wrong order it traps moisture and accelerates the freeze damage it was meant to prevent.
Questions
Caps & Dampers in Sandy — common questions
We hear scratching in the chimney in spring. What is up there?
Most likely birds nesting, sometimes squirrels or raccoons that got in through an uncapped flue. Do not light a fire to drive them out. Call us, and we remove what is there, clear the blockage and cap the flue so it does not happen again next year.
Our fireplace smokes only when the wind is up. Will a cap fix that?
Frequently, yes. Wind crossing an open flue top disrupts the pressure that carries smoke away, and a cap with the right overhang or a wind-directional design corrects it. We would rather try that than sell you masonry work for a problem that is aerodynamic.
Is a top-sealing damper worth it if the old one still moves?
If your existing damper closes and seals reasonably, no. If it is rusted, warped, or you can feel cold air in the room with it shut, a top-sealing damper is usually the better spend, because it closes the flue at the top and does the cap's job at the same time.
How often does waterproofing need redoing in Sandy?
A quality vapor-permeable repellent typically lasts several years, less on a chimney face that takes the weather hardest. The more important point is that it is not a substitute for a sound crown and cap. If those are failing, resealing the brick each year will not stop the damage.
Also in Sandy
Our other services here
Chimney Sweep Inspection Chimney Repair Fireplace Repair Installation Gas Fireplace Dryer Vents All Sandy services
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