For most historic Philadelphia rowhomes built before roughly 1920, lime mortar is the correct choice and modern Portland cement mortar is usually a mistake. Soft, hand-made brick was laid with soft lime mortar so the joints could flex, absorb movement, and act as the sacrificial part of the wall. Hard Portland cement is stronger than the brick around it, so instead of the joint wearing, the brick face cracks and spalls. Matching the mortar to the masonry is the most important decision in any repointing job on an older rowhome.

What lime mortar and Portland cement actually are

Lime mortar is made from lime, sand, and water. It’s soft, flexible, and breathable, and it cures slowly by reabsorbing carbon dioxide from the air. Portland cement mortar cures fast, gets very hard, and is far less permeable to water vapor. Portland became standard after the early 20th century because it’s strong and quick to set, which is great for modern block and concrete, but those same traits are what damage soft historic brick.

The golden rule: mortar should be softer than the brick

In a healthy masonry wall, the mortar is the weakest, most replaceable element. It’s meant to give a little, absorb thermal and moisture movement, and eventually erode so it can be repointed. Brick is expensive and permanent; mortar is sacrificial and renewable. When you fill a soft-brick wall with hard Portland mortar, you flip that relationship. The joints no longer give, so stress transfers into the brick, and the brick faces crack, bulge, and pop off. We see this constantly on rowhomes that were repointed with the wrong mix in the 1970s and 80s.

How to tell what your rowhome needs

A few clues point toward lime versus Portland:

• Age: Homes built before about 1920 were almost always laid in lime mortar.
• Brick hardness: Soft, hand-made brick that scratches easily needs soft mortar.
• Existing joint color and texture: Original lime joints are usually lighter, sandier, and softer than later cement repairs.
• Spalling near hard joints: If brick faces are popping right next to dense gray joints, that’s classic hard-mortar damage.

The safe approach is to match the original mortar’s strength, composition, color, and joint profile. On many Philadelphia rowhomes that means a lime-based or lime-rich mortar, sometimes with a small proportion of cement for workability, never a straight high-strength Portland mix.

Why matching mortar matters for the whole wall

Mortar isn’t just glue. It controls how the wall handles water and movement. The right mortar lets the wall breathe, dries out after rain, and flexes through Philadelphia’s freeze-thaw cycles. Get it wrong and you accelerate decay across the entire facade. That’s why our repointing crews test and match the existing mortar before grinding out a single joint, and why we handle matching brick replacement at the same time when faces have already spalled.

What it costs

Lime-based repointing is more labor-intensive than slapping in modern mortar, because it requires careful joint preparation, color and profile matching, and proper curing. Cost depends on the square footage, wall height and access, joint condition, and how much brick needs replacing. Small spot repointing is modest; full-facade work on a multi-story rowhome is a larger project. We don’t guess at numbers over the phone. Every job starts with a free on-site estimate, and you can browse finished work in our gallery.

What happens when you ignore failing joints

Mortar erosion doesn’t stay cosmetic for long. Once joints open up, water runs straight into the wall, and Philadelphia’s freeze-thaw cycles take over. Here’s the progression we see on neglected rowhomes:

1. Open joints. Wind-driven rain and runoff enter the wall through eroded mortar.
2. Saturation and freezing. Trapped water freezes, expands, and pushes brick and mortar apart.
3. Spalling. Brick faces pop off, exposing the soft, absorbent interior that soaks up even more water.
4. Structural movement. With enough joint loss, the wall can bulge, bow, or shift, which is far more expensive to correct than timely repointing.

Catching the wall at stage one or two is a straightforward repointing job. Letting it reach stage three or four turns it into brick replacement and, in the worst cases, partial rebuilding. The mortar is the cheap, renewable part of the wall by design, so replacing it on schedule is the single most cost-effective thing you can do for a historic rowhome.

Frequently Asked Questions

Is lime mortar always better than Portland cement?

Not always. Lime mortar is better for soft historic brick built before about 1920. Modern brick and block are designed for Portland cement. The rule is to match the mortar to the masonry, so the mortar stays softer than the brick.

What happens if my old rowhome was repointed with Portland cement?

Hard cement mortar is stronger than soft historic brick, so movement and stress crack the brick faces instead of the joints. You often see spalling and popped brick faces next to dense gray joints. The fix is to remove it and repoint with a properly matched softer mortar.

How do I know if my house used lime mortar?

Most Philadelphia rowhomes built before roughly 1920 were laid in lime mortar. Soft brick that scratches easily, lighter sandy-looking original joints, and the home’s age are all clues. A mason can confirm by testing the existing mortar.

Can you match my home’s original mortar color?

Yes. We match the original mortar in strength, sand color, and joint profile so repairs blend into the existing wall rather than standing out.