Why Plano chimneys age in their own particular way
North Texas is not kind to a masonry chimney, even though the fireplace season is brief. The summers run long and brutally hot, baking the brick and the crown day after day until the mortar dries and shrinks, then the occasional hard freeze of a Collin County winter snaps at whatever moisture has crept into those dried-out joints. That swing from triple-digit heat to a sudden overnight freeze is harder on masonry than a steady cold climate ever is, because the brick is constantly expanding and contracting across a huge temperature range. The crack you cannot see in July is the leak that shows up in January.
Then there is the ground itself. Plano sits on the expansive clay soil that defines so much of this region, the kind that swells when the spring rains come and shrinks back hard during the dry summer. That movement does not stop at the foundation. It travels up through the chimney structure, slowly working brick courses out of plumb, opening gaps at the crown, and shearing the bond between the chimney and the house. A great many of the leaning chimneys and stair-step mortar cracks we are called to look at in Plano trace straight back to clay soil heaving and settling under the chimney year after year, and that is a failure pattern you will not read about in a guide written for some other part of the country.