South Salt Lake · Salt Lake County
Caps, Dampers and Water Control on South Salt Lake Chimneys
Every problem an old brick chimney has starts with water, and water gets in at the top. Everything else on the repair list is downstream of that one fact.
What an open flue has been doing all these years
Plenty of chimneys in the older parts of the valley have never had a cap. Consider what that means over the life of the house. Every rainstorm sends water directly down the inside of the flue, where it soaks into unlined brick or sits on the shoulders of clay tile. Every winter that water freezes. The cast damper at the bottom rusts until it seizes, which is why so many houses here have a damper that no longer moves. Birds nest in the flue in spring and the nest becomes a blockage nobody knows about until the first fire of the year fills the room. In a built-up city like South Salt Lake that is usually pigeons and starlings rather than country birds, and they are far less seasonal about it, so a warm open flue can be occupied in January as readily as in April. Ash and soot combine with the moisture into an acidic sludge that attacks mortar joints from inside.
A cap stops all of that for a modest amount of money, which makes it the single best-value item on any old chimney's list. It has to be sized and fitted to the flue properly, with mesh that keeps animals out without choking the draft, and on the shorter chimneys common in this area the cap design can also help stabilize draft when air moves across the top.
Sealing brick that needs to breathe
Waterproofing an old chimney is where good intentions go wrong. Historic brick is porous by design and it relies on being able to dry outward. Coat it with a glossy film-forming sealer and moisture that gets in from the crown, from the flashing, or from inside the flue now has no way out. It sits behind the coating, freezes, and takes the brick face off from beneath. The result is a chimney that looks freshly treated and is deteriorating faster than before.
What we use instead is a vapor-permeable siloxane repellent, which soaks in and repels liquid water while still letting vapor pass. It is applied only after the crown, cap and flashing are sound, because none of it works while water is arriving from above. And on a chimney whose brick has already gone soft, we will tell you that repellent is not the answer and rebuilding the affected courses is, rather than selling a treatment that postpones a conversation.
Questions
Caps & Dampers in South Salt Lake — common questions
Our chimney has never had a cap and seems fine. Why add one now?
Because the damage is internal and slow. Rain going down an open flue rusts the damper, degrades mortar joints and invites nesting, and none of that is visible from the room. A cap is inexpensive relative to the repairs it prevents, which is why we recommend it before almost anything else.
Will mesh on the cap hurt the draft?
Correctly sized mesh will not. Mesh that is too fine, or a homemade screen added over an existing cap, will clog with soot and does restrict draft. We fit caps with an appropriate mesh aperture and we check them at the annual visit rather than assuming they have stayed clear.
Can we use a standard masonry sealer from the hardware store?
We would advise against it on old brick. Most consumer products form a surface film, which traps moisture in porous historic masonry and makes freeze damage worse. Look for a vapor-permeable siloxane repellent, and deal with the crown and flashing first regardless.
There is cold air pouring out of the fireplace all winter. Is a cap the answer?
A cap alone will not stop it. That air is coming down an open flue past a damper that no longer seals, which is very common in houses of this age. A top-sealing damper closes the flue at the top with a gasket and solves both problems at once.
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