For old, soft brick, typically anything made before the early 1900s, lime mortar is usually the better choice because it's softer and more breathable than modern Portland cement mortar, matching the brick's own softness instead of overpowering it. Old handmade brick was designed to work with lime mortar, and modern Portland cement mortar is significantly harder, which forces the softer brick itself to crack and spall as the wall moves and dries instead of the mortar joint absorbing that stress. It's not that Portland cement is bad mortar, it's the wrong hardness for that specific brick.
Historic brick, especially handmade or early machine-made brick from before roughly the early twentieth century, was fired at lower temperatures than modern brick, which leaves it softer and more porous. It was built to move with lime mortar, a mix that stays flexible and lets moisture pass through it (breathes) rather than trapping water inside the brick itself. That combination of a soft brick and a soft, breathable mortar is what let these buildings survive many decades of harsh winters in the first place.
Portland cement, developed later and now standard in most modern mortar, is much harder and less permeable. When it's used to repoint old soft brick, the mortar joint becomes harder than the brick around it, which is backwards from how the wall is supposed to work. Moisture that would normally pass harmlessly through breathable lime mortar instead gets trapped in the brick, and the brick, being the softer material, ends up cracking, spalling, or eroding faster than the mortar around it.
This is one of the most common repair mistakes Chelo's Brick & Stone runs into on older homes and chimneys around Independence and Galax: a previous repair used a hard, modern mortar mix on brick that needed something softer, and it accelerated damage instead of fixing it. Matching mortar hardness to the brick's actual age and softness is one of the first things we check before repointing historic masonry.
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Chelo's Brick & Stone serves Hillsville, Galax, Wytheville, Fancy Gap, and Independence, VA. Call for a straight answer and a free on-site estimate.
