You look up at your building and notice it: a face of brick has flaked away, or a crack runs through the mortar. So what causes bricks to crack or spall in Ontario, and how worried should you be?
In most cases the answer is water. Brick is tough, but Ontario’s freeze-thaw winters, road salt, and aging buildings give water plenty of chances to get in. Incompatible mortar, failed flashing, corroded steel, and building movement can make it worse.
This guide covers each cause, what the damage looks like, when it becomes a safety issue, and what to do next. If you’re seeing damage now, get a quote from Kavern and we’ll inspect it before it spreads.
Quick answer: Brick spalling is when the outer face of a brick flakes, peels, or pops off, exposing softer material underneath. Cracking is a separation that runs through the mortar joints or the brick itself. In Ontario, both are usually caused by trapped moisture and freeze-thaw cycles, sometimes combined with incompatible mortar, corroded steel, or structural movement.
What Causes Bricks to Crack or Spall in Ontario Buildings?
Eight causes account for most of the damage we see:
- Freeze-thaw cycles: water freezes inside brick and mortar and pushes the material apart
- Deteriorated mortar joints: worn joints let water into the wall
- Failed flashing, sealant, and drainage: water gets in and can’t get out
- Mortar that’s too hard for the brick: repairs that trap moisture
- Corroded lintels and shelf angles: rusting steel forces brick outward
- Building movement: missing expansion joints, settlement, and thermal stress
- Salt: de-icing salt and mineral salts crystallizing inside the brick
- Coatings and harsh cleaning: treatments that trap moisture or strip the brick’s hard outer skin
Freeze-thaw cycles
Brick and mortar are porous, so they absorb water. When that water freezes, it expands by about 9 percent and pushes against the brick’s internal structure. Ontario winters swing above and below freezing many times, and each cycle adds a little more stress.
Only wet brick is at risk. That’s why spalling often appears below window sills, on parapets, near grade, and on walls that stay damp. Our masonry restoration team sees the same pattern across the GTA.
Deteriorated mortar joints
Mortar is designed to be the sacrificial part of a masonry wall. It’s softer than the brick and wears first. Once joints recede or crumble, water enters the face of the wall and can travel behind it.
Repointing means replacing that mortar. It works best when it’s done before the brick itself starts to fail.
Failed flashing, sealant, and drainage
Many Ontario buildings use cavity walls, which rely on flashing and weep holes to send water back out. If flashing is missing or damaged, or weep holes are blocked, water sits in the wall and the brick stays saturated.
Water usually gets in at the details:
- Failed caulking and sealant around windows, doors, and joints
- Damaged copings or parapet caps
- Clogged eavestroughs and downspouts that dump water onto the wall
- Pooling water at sills and doorways
Our guide to commercial caulking and sealant restoration shows why the smallest detail is often the one that fails first.
Mortar that’s too hard for the brick
This one surprises many owners. When older, softer brick is repointed with hard, cement-rich mortar, the brick ends up doing the work the mortar should do. Moisture and stress get forced through the brick, and its face spalls.
Mortar should be softer and more permeable than the brick around it. Poor repointing from a previous repair is a common hidden cause, especially on older and heritage buildings.
Corroded lintels and shelf angles
On many mid-rise and high-rise buildings, steel supports the brick above windows and at floor lines. When that steel rusts, it expands well beyond its original size and pushes the brick outward.
Warning signs include:
- Horizontal cracks along a floor line
- Stair-step cracks at window corners
- Rust stains above openings
- Bulging brick
This isn’t cosmetic. It needs an engineer’s eyes.
Building movement
Brick veneer and the structure behind it expand and contract at different rates with temperature and moisture. Without movement joints, that stress has nowhere to go and shows up as cracks, often vertical ones near corners and openings.
Settlement is different. It usually produces stair-step or diagonal cracks that follow the mortar joints and widen in one direction.
Salt
De-icing salt splashes onto brick near entrances and grade, and water carries salts into the masonry. When the water evaporates, the salts crystallize inside the pores and exert pressure that flakes the surface.
The white powder you sometimes see is called efflorescence. It’s usually not structural by itself, but it tells you moisture is moving through the wall.
Coatings and harsh cleaning
Paint or film-forming sealers can trap water inside brick that’s already damp. Aggressive cleaning, like sandblasting, strips away the fired outer skin and leaves the softer brick underneath exposed.
How to Read the Damage
What you see on the wall usually points to the cause:
| What you see | Likely cause | What it usually needs |
|---|---|---|
| Brick faces flaking or popping off | Freeze-thaw with trapped moisture, salt, or hard mortar | Replace the brick, fix the water source, use compatible mortar |
| Stair-step cracks along mortar joints | Settlement or structural movement | Engineer review, crack repair, joint repair |
| Horizontal crack or bulge at a floor line | Corroded shelf angle | Engineer-directed repair of the angle and brick |
| Cracks or rust stains at window corners | Corroded lintel | Lintel repair or replacement, rebuild the brick above |
| Vertical cracks at corners or along long walls | Thermal or moisture movement, missing movement joints | Restore or add movement joints, repair cracks |
| White powdery deposits | Salts carried by moisture | Find and fix the moisture source, then clean |
| Crumbling, recessed mortar | Weathered joints | Repointing with matched mortar |
Concrete spalls for related reasons. If your building also has concrete elements, read about what causes concrete spalling in parking garages and balconies.
When Is Brick Damage a Safety Issue?
Treat it as urgent if you see any of these:
- Loose or shifted bricks
- Bulging or leaning wall sections
- Cracks that are growing, or where one side sits out from the other
- Damage above entrances, sidewalks, or walkways
- Missing brick near parapets or balcony edges
If pieces could fall, keep people away from the area below right away, then document the damage. Municipal property standards by-laws also generally expect owners to keep exterior walls in good repair.
What to Do When You Spot Cracked or Spalling Brick
- Photograph and log it. Note the date, elevation, floor, and location.
- Protect people below if any brick could fall.
- Look for the moisture source. Check rooflines, sealants, downspouts, sills, and grade.
- Get a condition assessment. A masonry condition assessment or a broader property condition assessment tells you what you have.
- Fix the cause first, then the brick. That means flashing, sealants, drainage, mortar, and brick replacement, in that order.
- Use matched, compatible materials. Mortar should suit the brick, and replacement brick should match color and texture.
- Schedule regular inspections. A spring check after winter catches damage early.
Boards and managers can find more in the commercial masonry restoration guide.
What Doesn’t Work
- Painting or sealing over damp brick: it can trap the moisture behind the coating
- Patching with hard cement: it looks fixed and often causes the next round of spalling
- Repointing only the worst joints: without asking why they failed
- Ignoring the roofline and flashing: the brick keeps getting wet
No surface treatment brings a badly spalled brick face back. In most cases the lasting fix is to replace the brick and correct the cause.
Spot Repair or Full-Wall Restoration?
Spot repair
Pros
- Quicker and targeted
- Useful when damage is isolated and the cause is known
Cons
- Damage returns if the cause is systemic, like failed flashing or movement
- Repairs can mismatch the wall over time
Full-wall restoration
Pros
- Addresses the cause across the whole elevation
- Consistent mortar, flashing, and detailing
- One round of access and scaffolding
Cons
- Needs more planning and engineering input
- A longer window of disruption for residents
Your engineer’s findings usually settle it. When damage has several causes, the full-wall approach tends to hold up better.
How Kavern Handles Cracked and Spalling Brick
Kavern Building Restoration is WSIB-certified and fully insured. We start with an inspection to find every problem area, then repair the cause and the brick together:
- Replacing failed wall flashing to keep water out of the cavity
- Repairing or replacing deteriorating brick
- Repointing with mortar matched to the existing wall
- Matching brick and mortar color, texture, and type for a seamless finish
We do this for condos, commercial buildings, and residential communities. See our masonry work at 108 Edgehill Drive.
[Add a first-hand note here: 2–3 sentences from Kavern’s masonry lead on a real wall. For example, what was causing the spalling at 108 Edgehill Drive and how the repair addressed it.]
We also work with engineers and architects, property managers, and owners and boards across Toronto, Etobicoke, Scarborough, and North York. To understand how water is getting into your wall in the first place, see what building envelope waterproofing is.
Frequently Asked Questions
What causes bricks to crack or spall in Ontario?
Mostly trapped moisture and repeated freeze-thaw cycles. Failed mortar, flashing, or sealants let water in, and corroded steel, hard mortar, salt, and building movement add to the damage.
Is brick spalling serious?
It can be. Spalling means moisture is already damaging the brick, and it usually gets worse. If the damage is above walkways or entrances, treat it as a safety issue.
What’s the difference between cracking and spalling?
Cracking is a separation in the mortar joints or brick. Spalling is the surface of the brick flaking or breaking away. They often occur together.
Can spalled brick be fixed without replacing it?
Badly spalled bricks are usually replaced, and the moisture source is corrected at the same time. Minor surface flaking may be monitored, but a mason or engineer should judge that.
Does freeze-thaw damage brick every winter?
Only wet brick is at risk. Damage builds over many cycles, which is why buildings with water problems deteriorate faster.
Are cracks in brick always structural?
No. Some hairline cracks are minor. Cracks that grow, form stair-steps, or leave one side offset should be reviewed by an engineer.
What is efflorescence, and is it harmful?
It’s a white salt deposit left behind when moisture evaporates. It’s usually not structural, but it signals that water is moving through the wall.
Can I stop spalling by sealing or painting the brick?
No. Coatings can trap moisture and make it worse. Fix the water source and replace the damaged brick.
Who is responsible for exterior brick repairs in a condo?
Often the corporation, since exterior walls are usually common elements, but your declaration decides. See who is responsible for balcony repairs for how this works, and the Condominium Authority of Ontario for guidance.
How quickly can I get a quote?
Kavern responds to every inquiry within one business day.
Conclusion
So what causes bricks to crack or spall in Ontario? Almost always it’s water, working through freeze-thaw cycles, failed joints, flashing, and sealants, and made worse by hard mortar, rusting steel, salt, and movement. Finding the real cause is what makes a repair last.
Seeing damage on your building? Get a quote right now. Call 905 503 5565 or request a quote online. Our team responds within one business day.