One side of a chimney almost always takes more weather than the rest, usually because it faces the prevailing wind and rain direction, gets more direct sun that drives temperature swings, or sits in more shade and stays damp longer than the other sides. Mortar and brick respond to whichever combination of sun, wind-driven rain, and shade they actually experience, so it's normal and expected for a chimney to show more wear on one face than the others.
Wind-driven rain rarely hits a chimney evenly. Whichever side faces the prevailing weather takes the brunt of driving rain, so that side's mortar joints see more direct water contact over time, which speeds up erosion on that face compared to a side that's more sheltered from wind and storms. This is separate from sun exposure, which affects a different set of sides depending on which way the chimney faces relative to the sun's path through the day.
Sun exposure and shade change how freeze-thaw cycling actually plays out on masonry. A side that gets more direct sun warms and cools faster and more often through a winter day, so it can run through more freeze-thaw cycles than a shaded side that stays at a steadier, colder temperature. A shaded, damp side has its own problem: it dries out more slowly after rain, so mortar there stays wet longer, which accelerates deterioration through a different mechanism entirely.
This is why we check every face of a chimney separately during an inspection rather than assuming one side represents the whole structure. It's common to find one side needing repointing well before the others, and repairing just that face, matching mortar color and joint style to the rest of the chimney, is usually all that's needed rather than redoing the whole thing at once.
More on this from Chelo's Brick & Stone.
Chelo's Brick & Stone serves Hillsville, Galax, Wytheville, Fancy Gap, and Independence, VA. Call for a straight answer and a free on-site estimate.
