Masonry Repair on Midvale Chimneys

Hard mortar in soft brick

Brick made in the early twentieth century was fired at lower temperatures than modern brick and is considerably softer. The lime-rich mortar it was laid in was softer still, and deliberately so. In a well-built old wall the mortar is the sacrificial component: it takes up movement, it lets moisture escape through the joint, and when it wears out you replace it and the brick survives another lifetime. Bring a hard modern portland mix into that wall and the whole arrangement is turned upside down. The joint ends up stronger than the units either side of it, so movement and trapped moisture have to find another way out, and the way they find is through the face of the brick. You see it as spalling in a neat line either side of a repointed joint, and it is permanent. On the older stock near the historic part of Midvale we match mortar by strength and composition, not by color alone.

What actually fails first

The crown, almost always. It is the concrete slab across the top of the stack, and its whole purpose is to throw water clear of the brick and the flue. A properly formed one is thick, sloped and overhangs with a drip edge. A quickly troweled one cracks, and after that every storm delivers water directly into the top of the chimney where nothing can dry it out.

Freeze-thaw along the valley floor

Midvale sits low and flat in the middle of the valley, near the Jordan River corridor where cold air settles at night. That produces plenty of crossings of the freezing point with the masonry still damp, which is the exact condition that breaks brick faces off. It is not the depth of cold that does the damage, it is the number of times it happens while the wall is wet.

Repair, rebuild, and being straight about which

Where the brick is sound and only the joints have gone, repointing is real, durable repair. Where the units themselves are failing, or the stack has moved, repointing is money spent on a surface that will not hold. Deterioration concentrates above the roofline, so rebuilding from the roof up is often the whole job rather than the whole chimney. We photograph what we find and show you which of the three situations you are in before there is a price attached to anything.