Repairing Orem's Post-War Chimneys

Thin above the roof, and unsupported

A characteristic of the ranch and split-level housing that fills much of this city is a chimney built as economically as the rest of the house. Above the roofline, where the structure loses the bracing that the building itself provides, many of these stacks are a single course of brick with no reinforcement inside. That was accepted practice. It also means the most exposed part of the chimney is the weakest part of it, and it is the part carrying the crown, the cap and whatever the wind does to it.

What we look for is lean, open joints on the windward face, and movement at the roofline where the flashing meets the brick. A stack that has taken a set is not going to straighten out, and a chimney visibly out of plumb above the roof is a rebuild rather than a patch. We would rather say that than repoint something that will keep moving.

Spalling follows the weather side

Look at a row of Orem chimneys and you will see the damage concentrated on particular faces. Wind-driven rain and snow wet one side more than the others, and the side that stays shaded through the short days does not dry between freezes. That combination pulls the fired face off the brick in flakes, exposing the soft interior, which then absorbs water far faster than the face ever did. Once that starts it accelerates, which is why a chimney can look tired for years and then deteriorate visibly in a single bad winter.

The chase cover problem on metal chimneys

Not every chimney here is brick. The framed and sided chases enclosing factory-built fireplaces have a metal pan on top called a chase cover, and on houses of this vintage that pan is usually galvanized steel. Galvanized rusts. A flat or nearly flat pan holds water in the middle, the rust starts there, and eventually it perforates and drains straight down inside the chase onto the framing and the top of the fireplace. Rust streaks running down the siding below the chase top are the tell. Replacement in stainless with a proper cross-break to shed water is a permanent fix rather than a repeat visit.

Smoke chamber parging

Inside the chimney, above the damper, is a tapered space called the smoke chamber that funnels the fire's output into the flue. It should be smooth. In a great many houses of this era it was left as stepped, raw corbelled brick, because it is out of sight. Those steps create turbulence, slow the draft and give creosote hundreds of ledges to collect on. Parging it smooth with refractory mortar improves how the fireplace draws and removes a genuine fire-load, and it is one of the few repairs whose result you can feel the first time you light a fire.