Repairing and Relining South Salt Lake Chimneys

Soft brick, soft mortar, and why the order matters

Brick made a hundred years ago is generally softer and more porous than what comes out of a plant today, and the lime-based mortar it was laid in was softer still. That was deliberate. In a wall built this way the mortar is the sacrificial part: it takes up movement, and when water freezes it is the joint that gives rather than the brick. Repoint that same wall with a hard modern portland mix and you invert the relationship. The joints become stronger than the units, movement and freezing stress now go into the brick faces instead, and within a few winters the faces start popping off. We see this on chimneys around the older parts of the valley regularly, and the giveaway is crisp new joints between crumbling brick. South Salt Lake is mostly small brick houses raised between the 1920s and the early 1950s on tight lots near the rail and industrial corridor, so the chimneys here are largely of one age and one construction, and they tend to arrive at the point of needing the joints cut out at roughly the same time.

Doing it properly means matching the strength and the permeability of the original, cutting the old joints back by hand rather than grinding through them, and accepting that the mortar we use will be softer than a builder's default. That is the point, not a compromise.

Relining a flue built for coal

The other half of the work here is what goes on inside. Many flues in this part of the valley are unlined brick, or lined with early clay tile whose joints have long since opened. Once that is the case, the chimney can no longer be relied on to contain heat or exhaust, and the practical remedy is a new liner sized for whatever is actually connected to it: a stainless liner for a wood appliance, or a properly sized liner for a gas water heater left on its own after a furnace changeover. Sizing is the part that gets ignored. A liner too large for the appliance recreates the condensation problem it was meant to solve.

What we will and will not recommend

On a chimney where the brick is sound and the joints are eroded, repointing with a compatible mortar is the right answer and it lasts a long time. Where the top courses have gone soft and the crown is broken up, taking the top down and rebuilding is honest work and pointing is not. Where a chimney is unused, unlined and going to stay unused, the cheapest defensible option is sometimes removing it to the roofline and sealing properly, and we will say so even though it is the smallest job on the list.