Salt Lake City · Salt Lake County
Capping and Sealing Wide Old Stacks in Salt Lake City
Most chimneys in this city were finished at the top with a sloped skim of mortar. That is not a crown, and after a century it is no longer even a slope.
What is actually on top of your chimney
A proper crown is a cast slab that overhangs the brickwork on every side and carries a drip edge, so water leaves the chimney clear of the masonry below. A mortar wash is a thin layer of mortar troweled over the top of the brick and finished flush. Almost every older Salt Lake City chimney has the second one.
Mortar wash cracks. It is thin, it has no reinforcement, and it is bonded directly to brick that moves at a different rate. Once cracked, it stops shedding water and starts collecting it, delivering it straight into the top of the stack and down between the flues. Most of the internal deterioration we photograph in this city started at the top and worked downward.
One cap over several flues
Old stacks here are wide and often carry two to four flue tiles. Fitting an individual cap to each tile leaves the crown exposed between them, which is where the water was getting in. A single multi-flue cap covers the entire top of the chimney, shelters the crown as well as the openings, and does it with one set of fixings.
It also solves the animal problem in one move. Open flues on tall old chimneys are attractive nesting sites in spring, and a nest is a blockage sitting directly above a firebox.
Downdraft on tall bench stacks
Homes on the higher ground east of the city sit where air moves down out of the canyon mouths, and a tall chimney standing in that flow can have its draft stalled or reversed by it. Where the pattern follows the wind rather than the weather, a wind-directional cap designed to use the moving air to induce draft rather than fight it is the correct answer, and it fixes fireplaces that no amount of firebox work would have improved.
Top-sealing dampers
Throat dampers in period fireplaces have generally corroded past sealing. A gasketed damper mounted at the top of the flue closes the chimney where the weather is, keeps the flue dry through the summer, and stops the constant loss of heated air in winter.
On waterproofing historic brick
Repointing and a sound crown do most of the work. Where a repellent is appropriate, it should be vapor permeable so the wall can still dry outward, and on historic brick it is worth testing an inconspicuous area first, because some coatings darken the masonry permanently.
Questions
Caps & Dampers in Salt Lake City — common questions
Our chimney top is just mortar and it is cracked. Does that need replacing?
If it has cracked through or lost pieces, yes. A cast crown with an overhang and drip edge sheds water away from the brickwork, which a flush mortar wash never did well and does not do at all once cracked. It is one of the highest-value repairs on an old chimney.
We have four flues in one stack. Do we need four caps?
A single multi-flue cap is usually the better answer. It covers all the openings and shelters the crown between them, which individual caps leave exposed. It is also easier to secure properly on a wide old stack.
Will a cap solve a chimney that downdrafts on windy days?
If the downdraft tracks the wind, a wind-directional cap is often the fix. If the fireplace also spills on still days, the cause is inside the house rather than on the roof, and a cap will not change it. The pattern tells us which one you have.
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Chimney Sweep Inspection Chimney Repair Fireplace Repair Installation Gas Fireplace Dryer Vents All Salt Lake City services
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