Foundation Cracks in Montreal: When to Worry & What to Do

Your home’s foundation is literally holding everything up—so when you spot a crack, it’s normal to have a mini heart attack. Are you looking at a minor cosmetic issue or the start of a structural nightmare?

At MTL Contractors, we know that foundation issues can be stressful and expensive if left unchecked. The good news? Not all foundation cracks in Montreal are bad—but knowing the difference can save you a lot of headaches (and cash). Let’s break it down.

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1. Are Foundation Cracks Normal?

Yes—some cracks are totally normal. Concrete naturally expands and contracts as it cures, which can lead to hairline cracks. However, some cracks can signal serious problems that need immediate attention.

✔ Hairline cracks (< 1mm wide) – Common in new homes or recently poured foundations. Usually harmless.

✔ Vertical cracks – Typically caused by natural settlement. If they’re small, they’re not a big deal.

✔ Diagonal cracks – Can be a sign of shifting or uneven settlement. Worth monitoring.

✔ Horizontal cracks – 🚨 Major red flag! Often caused by hydrostatic pressure (water pressure against the foundation), which can lead to wall failure.

✔ Wide cracks (> 6mm wide) – 🚨 These could mean serious structural movement. Time to call in the pros.

🚨 Pro Tip: If you can fit a dime into a crack, it’s time to get an inspection. If you can fit a loonie, it’s past time.

💡 Fun Fact: Montreal’s freeze-thaw cycles put extra stress on foundations. This is why preventative waterproofing is so important in our climate.

2. What Causes Foundation Cracks?

Foundation cracks don’t just appear out of nowhere—something caused them. Here are the most common culprits:

✔ Soil Movement – Expanding and contracting clay soil (common in Montreal) puts pressure on your foundation.

✔ Freeze-Thaw Cycles – Montreal winters = water freezing in small cracks, expanding, and making them worse.

✔ Hydrostatic Pressure – Poor drainage can cause water to push against your foundation, leading to horizontal cracks.

✔ Settling & Shrinking – Concrete naturally settles and shrinks over time, creating minor cracks.

✔ Tree Roots – Large trees near the foundation can suck moisture out of the soil, leading to shifting and cracks.

✔ Poor Construction – If shortcuts were taken when pouring the foundation, cracks will appear sooner than later.

🚨 Pro Tip: If your foundation cracks grow longer, widen, or leak water, they need professional attention.

3. When Should You Worry About Foundation Cracks?

Not all foundation cracks require panic, but some do. Here’s when to call in an expert:

🚨 Red Flags:

❌ Cracks wider than 6mm (thicker than a credit card).

❌ Cracks that run horizontally (sign of serious pressure issues).

❌ Cracks that keep getting bigger over time.

❌ Water seeping through cracks or damp spots inside the basement.

❌ Doors and windows sticking or not closing properly.

❌ Cracks near corners of the foundation (often serious structural issues).

If you see any of the above, it’s time to bring in MTL Contractors before the problem gets worse (and way more expensive).

💡 Reality Check: Small cracks may look innocent now, but if ignored, they can turn into big-dollar repairs later. Foundation problems don’t fix themselves.

4. How to Fix Foundation Cracks

The fix depends on the severity of the crack. Here’s how different types are repaired:

🔹 Small, Non-Structural Cracks (Hairline to 3mm wide)

✔ DIY Option: Injecting polyurethane sealant to prevent water infiltration. ✔ Best for: Cosmetic cracks that aren’t growing.

🔹 Moderate Cracks (3mm - 6mm wide, diagonal or stair-step cracks)

✔ Professional Injection: High-pressure epoxy or polyurethane injection to bond and waterproof the crack. ✔ Best for: Cracks that could worsen but aren’t yet critical.

🔹 Structural or Large Cracks (> 6mm, horizontal, or expanding cracks)

✔ Reinforcement Required: Steel braces, carbon fiber straps, or underpinning to stabilize the foundation. ✔ Best for: Foundations that are shifting, bowing, or at risk of failure.

🚨 Pro Tip: Never just “patch” a foundation crack without finding out what caused it. The crack is a symptom, not the disease.

5. How to Prevent Foundation Cracks

You can’t control Montreal’s weather, but you can take steps to protect your foundation.

✔ Improve Drainage – Keep water away from the foundation with proper grading and gutters.

✔ Install a Sump Pump & French Drain – Prevents water buildup that leads to hydrostatic pressure.

✔ Seal Small Cracks Early – Don’t wait for them to get worse.

✔ Avoid Large Trees Near the Foundation – Their roots can mess with the soil and cause shifting.

✔ Insulate & Waterproof Your Basement – Helps prevent freeze-thaw damage.

🚨 Pro Tip: If your basement is always damp or musty, you likely have water infiltration issues, even if you don’t see cracks yet.

Why Work With MTL Contractors?

Foundation repairs aren’t a DIY job if they’re serious. At MTL Contractors, we specialize in foundation crack repair, waterproofing, and structural reinforcements to keep your home solid for years to come.

Here’s what makes us different:

✅ Expert Structural Assessments – We don’t just patch cracks; we find and fix the cause.

✅ Licensed, Bonded & Insured – No cutting corners. No surprises. Just expert work, done right.

✅ Honest Pricing & No BS – We give you real numbers upfront, so you know what to expect.

✅ Waterproofing & Long-Term Solutions – We make sure the fix lasts.

If you’re seeing foundation cracks and aren’t sure what to do, let’s talk. Book a consultation with MTL Contractors today, and let’s keep your home standing strong.

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Foundation Cracks in Montreal: When to Worry & What to Do