Brick has a reputation for being tough, timeless, and basically “set it and forget it.” So when you notice a crack zig-zagging through a wall, splitting a mortar joint, or creeping across a brick face, it can feel confusing and a little alarming. The good news: most brick cracking has a real, understandable cause—and once you know what you’re looking at, prevention (and repair) becomes a lot more straightforward.
In this guide, we’ll walk through the most common reasons bricks and mortar crack, what those cracks are trying to tell you, and how to build (or maintain) brickwork so it stays solid for decades. We’ll keep it practical, with plenty of “what to check” steps you can use whether you’re a homeowner, a DIY renovator, or someone managing a property.
First, a quick reality check: brick rarely fails alone
When people say “the brick is cracking,” what’s often happening is a system issue. Brickwork is a combination of brick units, mortar, ties/anchors (in veneer construction), flashing and weep paths, the supporting structure behind it, and the soil and foundation below it. Cracks show up where stress concentrates—so the crack is usually a symptom, not the root cause.
That’s why two houses built with similar bricks can age very differently. One might stay crisp and straight; the other might develop stair-step cracking, bulges, or spalled faces. The difference is often moisture management, movement accommodation, and the quality of materials and workmanship.
Reading the crack: what the pattern usually means
Before you decide whether a crack is cosmetic or serious, it helps to read its “shape.” Crack patterns are like clues. They won’t diagnose everything on their own, but they can point you to the right suspects quickly.
Also, remember that brick walls can be structural (solid masonry) or non-structural (brick veneer). Veneer is essentially a cladding system that needs to drain and move a little. Solid masonry behaves differently. If you’re not sure what you have, look at window/door openings and wall thickness at a jamb, or check the basement/crawlspace where the wall meets the foundation.
Stair-step cracks along mortar joints
These are the classic “zig-zag” cracks that follow mortar joints in a step pattern. They often show up near corners, around windows, or where the foundation changes. A common cause is differential movement—one part of the wall or foundation is moving slightly differently than another.
That movement can come from soil settlement, seasonal expansion and contraction, or even structural changes like a new opening cut into the wall. The crack follows mortar because mortar is typically weaker than brick, so it’s the easiest path for stress to release.
Vertical cracks running straight up and down
Vertical cracks can be related to thermal movement (brick expands and contracts with temperature changes), shrinkage in mortar, or stress concentrations at wall ends. If the crack is narrow and fairly uniform, it may be movement-related and manageable with proper joints and flexible sealants.
If the crack widens toward the top or bottom, or if you see displacement (one side pushed out), it can indicate structural movement. In that case, it’s worth getting a professional assessment because the fix might involve the foundation, not just repointing.
Horizontal cracks in mortar beds
Horizontal cracks deserve attention. They can indicate corrosion of embedded steel (like lintels over windows/doors) or wall tie issues in veneer construction. When steel rusts, it expands, pushing masonry apart and cracking the mortar bed.
They can also show up where brick veneer is bearing incorrectly on something that moves differently (like a wood rim joist), or where there’s moisture freeze-thaw cycling in a saturated section of wall.
Cracks through the face of bricks (not just mortar)
When the brick unit itself cracks, it often points to higher stress, freeze-thaw damage, manufacturing issues, or impact damage. Bricks can also crack if they’re too hard relative to the mortar (yes, that can be a problem), or if moisture is trapped behind them and freezes.
Face cracking is also common when water management is poor—think missing flashing, clogged weeps, or sealants trapping moisture. The brick becomes a sponge, then winter does what winter does.
Moisture: the quiet troublemaker behind many cracks
If you only remember one thing, make it this: brick likes to get wet, but it hates staying wet. Brick is porous, mortar is porous, and the wall assembly is designed (or should be designed) to manage that reality. When water gets in and can’t get out, that’s when cracking, spalling, and bulging start to appear.
Moisture problems can be sneaky because the wall might look fine for years—until one harsh freeze-thaw season reveals what’s been building up behind the scenes.
Freeze-thaw cycles and spalling
In climates with real winters, water expands when it freezes. If brick or mortar is saturated and temperatures swing around freezing, that expansion creates internal pressure. Over time, the surface can flake off (spalling), corners can pop, and cracks can form across the brick face.
Prevention here is less about “waterproofing the brick” and more about keeping the wall from staying saturated. That means good flashing, working weep holes, proper caps on parapets, and avoiding sealers that trap moisture. Breathability matters.
Efflorescence as an early warning sign
That white, powdery residue on brick is called efflorescence—salts carried to the surface by moisture. On its own, it’s usually not structurally harmful, but it’s a sign that water is moving through the masonry.
If you see efflorescence paired with cracking or spalling, take it seriously. It suggests the wall is cycling wet-to-dry repeatedly, and in winter that can accelerate freeze-thaw damage. The fix is usually upstream: improve drainage and stop water entry rather than scrubbing the salts endlessly.
Missing or failed flashing and weep systems
Brick veneer walls should have a drainage plane and flashing that directs water out through weep holes. When flashing is missing, incorrectly lapped, punctured, or blocked, water can pool inside the wall cavity. That trapped water can rot wood framing, corrode ties, and create pressure that shows up as cracking.
Weep holes can also be blocked by mortar droppings (“mortar bridging”) or landscaping that sits too high. A simple check: find the weeps above grade and make sure they’re open, spaced appropriately, and not buried.
Foundation and soil movement: cracks that start below eye level
Brick is strong in compression but not very forgiving when the support beneath it shifts. Even small foundation movements can translate into visible cracking in masonry, especially around openings where stress concentrates.
Soil behavior is a big deal. Expansive clay, poor compaction, changing moisture conditions, and inadequate drainage can all cause the ground to move seasonally or over time.
Differential settlement
Differential settlement happens when one part of the foundation settles more than another. This can be due to variable soil conditions, poor drainage concentrating water in one area, or changes like a new driveway, patio, or addition affecting how water flows.
Brick cracking from settlement often shows up as stair-step cracks that widen toward one end, or cracks that radiate from corners of windows and doors. Monitoring matters: take photos, measure crack widths, and watch for changes over a few months—especially across seasons.
Frost heave and poor drainage
When water-saturated soil freezes, it can expand and lift parts of a foundation or slab (frost heave). Even if it settles back, the repeated movement can fatigue masonry and open up cracks over time.
Good grading, downspout extensions, and perimeter drainage reduce the amount of water that can freeze near the foundation. If your downspouts dump water right at the base of the wall, you’re basically feeding the problem.
Tree roots and shifting loads
Trees can affect foundations in two ways: roots physically displacing soil and structures, and roots changing soil moisture (especially in clay soils). Removing a mature tree can also change moisture balance and trigger movement as soil rehydrates.
Load changes matter too. If you add a second story, install heavy stone features, or change interior supports, the foundation may respond—sometimes in ways that show up as masonry cracking first because it’s brittle compared to wood framing.
Thermal movement: brick expands more than you might think
Brick and mortar expand and contract with temperature changes. Over long runs of wall, that movement adds up. If the wall doesn’t have proper movement joints (expansion joints/control joints), the stress has to go somewhere—and it often shows up as cracking.
This is especially common on long, uninterrupted stretches of veneer, on sun-exposed elevations, and on walls with dark brick that heats up more.
Missing expansion joints in veneer walls
Brick veneer needs vertical expansion joints at intervals and at transitions (like corners, step-backs, or changes in backing materials). Without them, the veneer can “grow” and push against itself, causing diagonal cracking, bulging, or compressed mortar joints.
Homeowners sometimes unknowingly make this worse by filling existing expansion joints with hard mortar during repairs. Those joints need flexible sealant and backer rod—not mortar—so they can actually move.
Different materials moving at different rates
Brick, concrete, steel, and wood all move differently with temperature and moisture. Where they meet—like at a brick-to-siding transition, around steel lintels, or at concrete ledges—movement can concentrate stress.
Detailing matters here: slip joints, flashing, and flexible sealants at transitions can prevent cracks. If you see cracking right where two materials meet, it’s often a sign that the joint wasn’t designed to accommodate movement.
Mortar problems: strength isn’t always your friend
Mortar is supposed to be the “sacrificial” element in many masonry systems. Ideally, mortar is slightly softer and more permeable than the brick, so it can absorb minor movement and allow moisture to escape. When mortar is too hard or incorrectly mixed, it can force the brick to take the stress instead—leading to cracked faces and spalling.
Mortar issues are common in repairs, where someone uses a strong modern mix on older, softer brick. It looks fine at first, then the brick starts to fail because it can’t “compete” with the mortar.
Using the wrong mortar type for the brick
Older homes often used lime-rich mortars that are more flexible and breathable. Repointing them with a hard Portland-cement-heavy mortar can trap moisture and concentrate stress in the brick units.
If you’re dealing with heritage masonry or older brick, matching the mortar is crucial. That means matching not just the color, but the strength and permeability. A proper assessment might include mortar testing, especially on significant projects.
Poor mixing, too much water, or inconsistent batches
Mortar that’s mixed too wet can shrink more as it cures, leading to hairline cracking and weaker joints. Inconsistent batching can create sections that cure differently, which can show up as random cracking patterns or uneven joint deterioration.
For larger jobs, consistency is easier when materials are measured carefully and mixed the same way each time. When concrete work is part of the project—like footings, pads, or structural supports—using a consistent supply like ready mix concrete can help reduce variability that sometimes leads to movement and cracking in adjacent masonry.
Raking joints too aggressively during repointing
Repointing is great when done right, but aggressive grinding can damage the edges of bricks, widening joints and creating weak contact surfaces. That can make new mortar less effective and increase the chance of cracking.
A careful approach—using appropriate tools, controlling depth, and avoiding brick damage—helps the new mortar bond properly and perform as intended. It also keeps the wall looking sharper, since over-wide joints can change the whole character of the brickwork.
Structural details that commonly trigger cracking
Some cracks aren’t about general movement—they’re about specific stress points created by missing or failing structural details. Brickwork needs proper support over openings, stable bearing surfaces, and corrosion-resistant components.
When one of those pieces is missing or deteriorates, cracks often appear in predictable places: above windows, at door corners, and along shelf angles or ledges.
Lintel corrosion above doors and windows
Steel lintels support brick above openings. When they rust, they expand and jack the masonry upward, cracking the mortar bed and sometimes pushing bricks out of plane. You might notice a horizontal crack, rust staining, or a slight “smile” of the brickwork above the opening.
Prevention includes proper flashing over lintels, end dams, and keeping water from sitting on steel. If corrosion is already happening, repairs may involve cleaning/replacing the lintel and rebuilding affected brickwork—not just patching the crack.
Improper bearing or overloaded brick ledges
Brick veneer is often supported on a foundation ledge or shelf angle. If that support is insufficient, uneven, or compromised by settlement, the veneer can crack or bulge. Overloading can also happen when someone adds heavy features (like stone caps or thick stucco layers) without confirming support.
Look for cracking that aligns with floor lines, ledges, or changes in wall thickness. Bulging is a red flag—if the wall is moving outward, it can indicate tie failure or loss of support and should be evaluated promptly.
Wall tie corrosion or failure in veneer construction
In a veneer wall, metal ties connect the brick to the backing structure. If ties corrode (often due to trapped moisture) or were installed incorrectly, the veneer can become unstable. Cracking, bulging, and “drummy” sounding brick (hollow when tapped) can be signs.
Prevention again circles back to moisture management: keep the cavity draining, avoid mortar bridging, and ensure flashing and weeps are doing their job. In coastal or high-exposure environments, tie material selection becomes even more important.
Workmanship issues: small shortcuts that become big cracks
Even with decent materials and a solid design, workmanship can make or break brick performance. Brickwork is detail-heavy: mortar coverage, joint tooling, curing conditions, and alignment all matter. A few rushed steps can set the stage for cracking later.
If you’re hiring out masonry work, it’s worth knowing what good practice looks like so you can ask better questions and spot red flags early.
Inadequate curing in hot, cold, or windy weather
Mortar needs time and the right conditions to hydrate and gain strength. If it dries out too fast in heat or wind, it can shrink and crack. If it freezes before it cures, it can be permanently weakened and prone to crumbling and cracking.
Good masons adjust their approach based on weather: protecting fresh work, controlling moisture, and using appropriate cold-weather or hot-weather techniques. If a project is being rushed through poor conditions without protection, cracking risk goes up.
Improper joint tooling and water shedding
Tooling isn’t just for looks. Properly tooled joints compress the mortar and help shed water. Poorly finished joints can hold water, increasing saturation and freeze-thaw risk.
Joint profiles matter: a concave joint generally performs well for weather resistance. Raked or flush joints can be more vulnerable in exposed areas unless the wall is well protected and detailed.
Mortar bridges and clogged cavities
In veneer walls, mortar droppings can fall into the cavity and create bridges that allow water to reach the backing wall. Over time, that can lead to moisture damage, corrosion, and cracking.
Best practice includes using cavity nets or mortar collection devices and keeping weep paths clear. If you’re seeing moisture inside or chronic efflorescence outside, cavity blockage is one possible cause worth investigating.
Material quality: choosing brick and accessories that fit the job
Not all bricks are created equal. Different manufacturing methods, absorption rates, and durability ratings can affect how brick performs in a specific climate and exposure. The same goes for mortar sand quality, sealants, flashing, and metal components.
When you’re building new or doing a major repair, selecting materials that match your environment (freeze-thaw exposure, wind-driven rain, coastal air, etc.) is a big part of preventing future cracking.
Absorption rate and durability ratings
Bricks with high absorption can be more vulnerable in freeze-thaw climates if the wall assembly doesn’t manage moisture well. That doesn’t automatically mean “don’t use them,” but it does mean you need to be thoughtful about detailing and exposure.
If you’re sourcing materials locally and want guidance on options, talking with a reputable brick supplier Toronto can help you compare brick types, ratings, and finishes that make sense for your project’s conditions.
Matching brick hardness to mortar (and to the building)
It’s tempting to think harder is always better, but masonry systems work best when components are compatible. Overly hard brick paired with weak mortar can lead to joint cracking; overly hard mortar paired with softer brick can lead to brick failure.
For repairs, matching existing materials is often the safest path. If you’re mixing old and new brick, consider how the new units will behave next to the old ones in terms of absorption and thermal movement.
Corrosion-resistant metals and smart detailing
Lintels, ties, shelf angles, and fasteners should be selected for the exposure level. In many cases, galvanized or stainless steel components are worth the upgrade because corrosion is such a common driver of cracking.
Just as important: those metals need to be detailed so water doesn’t sit on them. Flashing, drip edges, end dams, and proper slopes are the unglamorous details that keep brickwork looking great long-term.
Prevention checklist you can actually use
If you’re planning new brickwork—or trying to keep existing masonry in good shape—here’s a practical set of prevention steps. You don’t need to do everything at once, but even a few improvements can reduce cracking risk significantly.
Think of this as “reduce water, allow movement, maintain support.” Most brick cracking problems fall into one of those buckets.
Keep water moving away from the wall
Start with the basics: make sure gutters are clean, downspouts discharge well away from the foundation, and the ground slopes away from the building. These simple steps reduce saturation in both the wall and the soil beneath it.
Check for sprinklers hitting brick regularly, hose bib leaks, and garden beds piled too high against the wall. Brick that’s constantly damp is brick that’s more likely to crack when temperatures swing.
Maintain the wall’s drainage paths
Find and clear weep holes. If they’re missing entirely on a veneer wall, that’s a red flag worth investigating. Look for signs of blocked cavities: persistent efflorescence, damp interior spots, or cracking concentrated near the base of walls.
Also check caps and copings on chimneys and parapets. These are high-exposure areas where water entry is common, and failures there can send moisture down through the wall, leading to cracking far below the actual leak.
Respect movement joints and flexible transitions
If your wall has expansion joints, keep them functional. Don’t mortar them shut. If sealant is old and failing, replace it with the right type and install backer rod so the sealant can stretch properly.
At transitions—brick to siding, brick to concrete, brick around windows—use the right sealant details so movement doesn’t become cracking. This is especially important on sun-baked walls where thermal cycling is intense.
When a crack shows up: how to respond without guessing
Seeing a crack doesn’t automatically mean you need a full rebuild. The key is to figure out whether the crack is stable (old movement that’s stopped) or active (movement that’s ongoing). Your response should match the cause.
If you’re ever unsure—especially if cracks are growing, wide, or paired with bulging—get a qualified mason or structural professional involved. It’s cheaper to diagnose early than to rebuild later.
Measure, mark, and monitor
Take clear photos with a ruler for scale. Measure crack width at a few points and write the date down. You can even place a small pencil mark across the crack to see if it shifts over time.
Watch for seasonal changes. Some cracks open slightly in winter and close in summer (or vice versa). That can indicate thermal movement rather than settlement, which changes the repair strategy.
Decide whether it’s mortar-only or brick damage
If the cracking is mostly in mortar joints and the bricks are intact, repointing may be enough—assuming the underlying cause (like water entry) is addressed. If bricks are spalling or cracking through the face, you may need brick replacement and a deeper look at moisture exposure.
A quick tip: if mortar crumbles easily to dust, it may be too weak or weathered. If it’s extremely hard and the brick is failing, the mortar may be too strong for the brick. Both scenarios can be fixed, but they require different approaches.
Know when it’s time to call in help
Call a pro if you see bulging, step cracking that’s widening, horizontal cracks near lintels with rust staining, or cracks paired with sticking doors/windows (which can indicate structural movement). Also call if you see water getting behind the wall—because moisture is often the accelerant that turns small cracks into big repairs.
If you’re sourcing materials or looking at repair options, visiting a local mason yard can be surprisingly helpful. You can compare brick matches, ask about mortar compatibility, and get practical guidance on what products suit your wall and climate.
Smart upgrades that reduce cracking risk long-term
If you’re already doing work on a brick wall—maybe repointing, replacing a lintel, or rebuilding a section—this is a great time to add small upgrades that improve performance. These upgrades often cost less than you’d expect because the wall is already open or being worked on.
Think of it like adding “insurance” to the system: better drainage, better corrosion resistance, and better movement accommodation.
Improve flashing details where water loves to sneak in
Windows, doors, roof-to-wall intersections, and parapets are common leak points. Proper flashing with end dams and correct laps makes a huge difference. If you’re rebuilding above an opening, it’s often worth upgrading the flashing and drip edge details at the same time.
On chimneys, consider the crown/cap condition and counterflashing at the roofline. Water entry at the top can show up as cracking much lower down, so addressing the source is key.
Upgrade lintels and ties to resist corrosion
If corrosion caused cracking once, it can do it again. Using corrosion-resistant metals and ensuring they’re protected by flashing reduces the chance of repeat failures. This is especially important in wet, salty, or high-exposure environments.
Also make sure steel components aren’t acting like little gutters. A tiny slope or drip detail can prevent water from sitting on metal and starting the rust cycle.
Repoint with compatible mortar and good joint profiles
Repointing isn’t just “fill the gaps.” The mortar choice, joint preparation, and tooling all matter. Compatible mortar helps the wall handle movement and moisture without transferring stress into the bricks.
And don’t underestimate the value of a properly tooled joint. It sheds water better, resists erosion, and helps the wall stay drier—reducing the conditions that lead to freeze-thaw cracking.
Brick can last a very long time, but it needs a wall system that respects water, movement, and material compatibility. If you treat cracks as clues instead of just cosmetic flaws, you’ll usually find a clear path to prevention—and a brick wall that stays strong and good-looking through many more winters.
