Masonry Repair for Alpine's Exposed Stacks

The mechanism, in one paragraph

Brick and mortar are porous. They take on water during a storm or a thaw, and when the temperature drops below freezing that water expands by roughly a tenth of its volume with nowhere to go. A single winter night of that is invisible. A few hundred cycles spall the brick face, open the mortar joints and lift the crown. Alpine sits at the top of Utah County's elevation range and against the bench, which means more nights below freezing and more days that climb above it. This town gets more freeze-thaw cycles per winter than the valley floor does, and the masonry keeps the score.

North faces fail first

On a chimney, damage is rarely even. The north and northeast faces of a stack see almost no direct winter sun, so meltwater that soaks in during a warm afternoon does not dry before nightfall. It simply refreezes in place. Walk around an older Alpine chimney and you will usually find one face where the mortar is recessed and the brick edges have gone soft, and three faces that look fine. That is not bad workmanship. That is aspect.

Start at the crown, because it is nearly always the crown

The crown is the sloped concrete cap on top of the masonry, and its whole job is to throw water clear of the brick. Most crowns we find in Alpine were poured thin, flush with the brick, with no overhang and no expansion joint around the flue tile. They crack, and once they crack they stop being a roof and start being a funnel. Water then travels down inside the stack, gets into the top courses and the smoke chamber, and shows up as staining on a ceiling six feet away from anything obviously wrong.

Sealing a hairline crack is cheap. Re-casting a crown with a proper overhang is a day. Rebuilding the top several courses because water worked on them for a decade is a different conversation, and which one you are having is decided by how long the crack ran.

Repointing, rebuilding, and telling you which

We repoint where the brick itself is sound and only the joints have eroded. We rebuild from a solid course upward where the brick has spalled through its hard outer face, because pointing around crumbling brick puts good mortar next to material that will fail again next winter. When a stack is on the line between the two we will say so and show you the photographs rather than pick the larger job by default.

Waterproofing that lets masonry breathe

After repair we recommend a vapor-permeable masonry sealer, not a film-forming one. A sealer that traps moisture inside the brick makes the freeze-thaw problem worse, not better, and that mistake is not reversible.