Salt Lake City · Salt Lake County
Restoring and Rebuilding Salt Lake City Chimney Stacks
Two things make chimney repair different in this city: the stacks are taller and older than anywhere else we work, and the ground they stand on is seismically active.
Unreinforced masonry in a seismic valley
The Wasatch Fault runs along the eastern edge of the Salt Lake Valley, and the older housing here was built long before anyone designed for that. A tall brick chimney with no steel in it is a stack of individual units held together by mortar, cantilevered above the roof, carrying its own weight and nothing holding it laterally. In an earthquake, unreinforced masonry chimneys are among the first elements of a house to fail, and they fail by breaking at the roof line and falling.
That is not a reason to panic about your chimney. It is a reason to be honest when the mortar is already soft and the stack is already tall, because a chimney in that condition is a poor candidate for another few decades of neglect. Where a rebuild is happening anyway, it is worth discussing what can be done to improve on how it was originally built.
Historic districts
A number of older Salt Lake City neighborhoods fall within local historic districts, and exterior alterations in those areas can be subject to review. In practice this affects chimney work mostly in terms of appearance: matching brick, matching mortar color and joint profile, and not changing the visible form of a stack. It is worth checking with the city before committing to a change in how a chimney looks, and it is one of the reasons we default to matching the existing work rather than modernizing the look of it.
The work itself
- Repointing failed joints, which on soft historic brick means a mortar chosen to be weaker than the brick rather than stronger, so the joint remains the sacrificial element it was designed to be.
- Replacing spalled and delaminated units with brick matched for size, color and texture.
- Recasting the crown. Very few chimneys of this age have a proper crown; most have a sloped mortar wash that cracked decades ago.
- Correcting flashing that was surface-mounted and sealed instead of let into the masonry.
- Rebuilding from the roof line where the stack has lost too much section to be repointed.
Being straight about scope
Old chimneys generate long lists. We separate what is structural from what is cosmetic, and we would rather do the top of a stack properly this year than the whole thing badly across two. If a chimney no longer serves anything and is deteriorating, taking it down below the roof line is a legitimate option and we will say so.
Questions
Chimney Repair in Salt Lake City — common questions
Should we be worried about our chimney in an earthquake?
It is worth a realistic look rather than worry. An old unreinforced stack in poor condition is more vulnerable than one that has been maintained, and if you are rebuilding anyway it makes sense to discuss reinforcement at that point. An inspection tells you which category yours is in.
Do we need approval before repairing a chimney on a historic home?
Repairs that match the existing appearance are generally the least complicated route, but rules vary by district and by what you are changing, so check with the city before altering the visible form or materials. We build to match by default, which usually keeps the question simple.
Why can we not just use strong modern mortar?
Because mortar harder than the brick around it stops absorbing movement and moisture, and the brick face takes that stress instead. On soft historic brick that produces spalling within a few years. The correct repointing mortar is deliberately weaker than the units it joins.
How do we know whether the stack needs repointing or rebuilding?
It turns on whether there is enough sound brick left for new mortar to key into. Where the units are solid and only the joints have eroded, repointing is the right and much cheaper answer. Where brick faces have spalled away, courses have shifted, or the stack moves under hand pressure, repointing has nothing to hold and rebuilding from the roof line is the honest recommendation.
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