Repointing sounds simple enough: scrape out the old mortar, pack in the new, done. But we've walked into more NYC brownstones and rowhouses than we can count where a well-meaning repointing job went sideways, and the brick paid the price. Repointing brickwork is one of those tasks that looks like a weekend DIY project until you're staring at cracked brick faces, crumbling joints, or a wall that's actively trapping moisture behind a mortar cap it was never designed to wear. The truth is, most repointing failures come down to a handful of avoidable mistakes: the wrong mortar mix, sloppy joint prep, careless power tool use, bad timing with the weather, and skipping the curing process altogether. Get any one of these wrong, and you're not fixing your brick. You're setting up the next repair job, usually a more expensive one.

Below, we're breaking down exactly where repointing projects go wrong and what it actually takes to do it right.

Choosing and Applying the Wrong Mortar Mix

If there's one mistake that causes the most long-term damage, it's this one. Mortar is supposed to be the sacrificial layer in a brick wall. It’s meant to wear down and get replaced over time so the brick itself stays intact. When you flip that relationship by using a mortar that's harder than the brick, you've essentially told the wall to sacrifice the brick instead.

1. Using hard cement on soft bricks

This is the single most common and most damaging repointing mistake we see. Older NYC buildings, especially anything built before the mid-20th century, were laid with softer, more porous brick and lime-based mortar that could flex slightly with temperature swings and settling. Modern Portland cement mixes are far more rigid. When that rigid mortar is packed into joints between old, soft brick, the wall no longer has anywhere to release stress. Instead of the mortar joint absorbing the movement, the brick face takes the hit in the form of cracking, spalling, or crumbling at the edges. Once a brick face has blown out like that, you can't just repoint around it. You're now looking at brick replacement, which is a far bigger and costlier job than the pointing work that started it.

2. Getting the water ratio wrong. 

Mortar consistency matters more than people think. A mix that's too wet will shrink as it dries, and that shrinkage creates hairline cracks that let water in, which, in a New York winter, means freeze-thaw damage down the line. A mix that's too dry, on the other hand, won't bond properly to the brick surface at all. It'll sit in the joint looking fine for a few weeks and then start falling out in chunks. The right consistency should hold its shape without slumping but still be workable enough to pack tightly into the joint without leaving voids.

3. Ignoring the original composition 

Every brick wall has a mortar "recipe" baked into its original construction, and that recipe was chosen for a reason, usually to match the flexibility, breathability, and appearance of the brick it's holding together. On historic or older buildings, that almost always means a lime-based mortar rather than a modern, rigid cement blend. Lime mortar breathes. It lets moisture that gets into the wall escape through evaporation instead of trapping it behind an impermeable barrier. When a contractor swaps in a generic Portland cement mix without checking what the wall actually needs, you end up with a wall that looks patched but is quietly holding onto moisture it can't release, which shows up later as spalling, efflorescence, or interior dampness.

The fix here isn't complicated, but it does require some diligence: match the new mortar's hardness and composition to the original as closely as possible, test the mix before committing to a full wall, and don't assume "stronger" mortar means a better repair. In masonry, stronger isn't always better, but it's often the opposite.

Poor Joint Preparation and Depth Errors

Repointing isn't just about filling gaps. It is about creating a joint deep enough and clean enough for the new mortar to actually anchor itself. Skip this step or rush it, and no mortar mix, however well-chosen, is going to hold.

1. Not removing enough old mortar.

 A shallow scrape-and-fill job is one of the most common shortcuts we see, and it's also one of the most short-lived. Old, decayed mortar needs to be raked out to a depth of roughly one to two times the width of the joint, not just skimmed off the surface. If you don't get down to solid, sound mortar, the new material has nothing to grip onto. It'll sit as a thin cosmetic layer on top of crumbling material underneath, and it won't be long before that layer cracks, pops loose, or washes out entirely. Depth is what gives the new mortar mechanical anchorage into the wall, and there's no substitute for doing that removal properly.

2. Over-clearing with power tools. 

On the flip side, going too aggressive with an angle grinder creates its own set of problems. It's tempting to speed through joint removal with a grinder, especially on a large wall, but careless technique chips and scars the brick edges (called "arrises") on either side of the joint. Once those crisp brick edges are chewed up, there's no putting them back. You've permanently widened the joint and changed the look of the wall. Grinders can also generate enough heat and vibration to stress hairline cracks in older, more brittle brick. The safer approach is to use tools sized correctly for the joint width, keep the blade centered in the mortar joint, and finish the last bit of removal by hand with a chisel to avoid touching the brick face at all.

3. Failing to clean out dust. 

This one gets overlooked constantly. After grinding or raking out old mortar, the joint is full of fine dust and debris, and if that dust stays put, the new mortar can't form a real bond with the brick surface. Instead, the new mortar effectively bonds to a layer of loose grit sitting on top of the brick, which is a bond that fails fast. Every joint needs to be flushed out with water or blown clean with compressed air immediately before repointing. It's a five-minute step that gets skipped constantly, and it's a major reason repointing jobs fail within a year or two instead of lasting decades.

Neglecting Weather and Curing Conditions

Even with the right mortar and perfectly prepped joints, timing can still sink a repointing job. Mortar is a chemical process that cures through a hydration reaction, not simply by "drying out." And that process is extremely sensitive to temperature and moisture conditions during and after application.

1. Working in extreme temperatures.

Cold and heat both cause problems, just in opposite directions. Repoint in freezing weather, and the moisture in the fresh mortar can literally expand and shatter the joint before it's had a chance to cure, that's a total loss, not a minor flaw. On the other end, applying mortar in high heat or direct, harsh sun causes the surface to dry out far too fast before the internal curing process has caught up. That mismatch between surface drying and internal curing weakens the whole joint and leads to a soft, chalky mortar that never reaches full strength. The window for safe application is narrower than most people assume, and in New York, that often means planning around both summer heat waves and winter cold snaps rather than working straight through the calendar.

2. Skipping pre-dampening. 

Dry, porous brick is thirsty. If you pack fresh mortar into a joint without wetting the surrounding brick first, the brick will pull moisture straight out of the new mortar before it's had time to cure properly. That moisture loss disrupts the hydration process and leaves you with a weaker, more brittle joint. Lightly dampening the brick surface before application, enough to knock down its absorbency without leaving standing water, gives the mortar a fighting chance to cure the way it's supposed to.

3. Failing to protect the final work. 

Fresh mortar is vulnerable for days after it goes in, not just hours. Heavy rain can wash out the surface before it's set, and strong wind can dry it too quickly, similar to the heat issue above. A rushed job that skips covering or shielding freshly pointed areas during that early curing window often looks perfectly fine on day one and starts failing within weeks. Covering the work with burlap or plastic sheeting, and keeping it lightly misted in hot weather, protects that curing process long enough for the mortar to reach real strength.

Conclusion

Repointing brickwork isn't a project where "close enough" holds up over time. The mistakes that cause the most damage, mismatched mortar hardness, shallow joint prep, careless tool use, and ignoring weather and curing all of them don't usually show up as failures on day one. They show up six months or two years later, as cracked brick faces, crumbling joints, or water damage that's now working its way into the wall itself. And by that point, the fix is almost always bigger and more expensive than the repointing job that started it.

If your building's mortar joints are showing their age, crumbling, receding, or letting water through, it's worth having someone assess the brick itself, not just the joints, before any work begins. NY Vanta Contractors handles brick pointing and masonry repair across NYC, with an eye toward matching mortar composition to the original brick so the fix actually lasts.