Structural Vs. Non-Structural Cracks: How To Identify & Fix

Noticing a crack in your basement or foundation wall can be alarming. As a homeowner in Toronto and the GTA, you might immediately jump to the worst-case scenario: Is my home’s foundation failing?

The good news is that not all cracks are created equal. While any crack signals a potential issue that needs monitoring, understanding the difference between a structural crack and a non-structural crack is the first crucial step toward effective repair and peace of mind.

At DGI Waterproofing, we’ve spent years inspecting and repairing foundation cracks right here. We want to walk you through everything you need to know, just as we would during a personal consultation, so you don’t have to keep guessing (or Googling!).

Understanding The Difference Between Structural & Non-Structural Cracks

When you look at a crack, the question we are asking is this: Is this crack a result of the home moving, or is it a result of the concrete simply drying?

This distinction – movement vs. drying -is the simplest way to differentiate the two types of cracks. It defines their origin and their threat level to your home’s stability:

Structural Cracks: These are cracks that indicate there has been movement in the foundation. They directly threaten your home’s structural integrity and stability.
Non-Structural Cracks: These are cracks that indicate concrete shrinkage during the curing process, or very minor, expected settlement. They do not compromise the structural integrity of your home.

Let’s take a closer look at what each type of crack really means for your property.

What is a Non-Structural Crack?

A non-structural crack is often cosmetic or a sign of minor, expected movement. They are common, especially in new construction, and do not threaten the stability or load-bearing capacity of your home. Think of them like a wrinkle on your wall—they don’t ruin the structure, but they can still cause problems, primarily related to water intrusion. While not an immediate structural emergency, we strongly recommend having them sealed because even a hairline crack is an open door for water.

Causes of Non-Structural Cracks:

Concrete Shrinkage & Curing: This is the most frequent cause. As the concrete dries and cures (especially in new homes within the first year), it naturally shrinks. This internal tension creates hairline cracks.
Minor Settlement: All homes settle slightly over time. Small, natural settling of the building can cause minor cracks, which typically appear soon after construction.
Creep Damage: This refers to the slow, long-term deformation or movement of building materials under sustained stress, leading to minor cracks.
Hydrostatic Pressure: If water builds up against the foundation wall, the pressure can cause minor cracks to form. This water buildup is also what often pushes water through the newly formed cracks.
Temperature & Moisture Fluctuations: Seasonal changes, especially the extreme heat and cold we experience in Toronto, cause materials to expand (heat) and contract (cold). This cyclical movement can lead to the formation or widening of non-structural cracks.
Vegetation Interference: Roots from nearby trees and plants can draw moisture from the soil near the foundation, causing minor, localized soil movement and impacting the foundation perimeter.

What is a Structural Crack?

Structural cracks are the ones that demand immediate attention. They are a clear indication of a deeper underlying issue that is causing significant stress, movement, or instability in your foundation’s load-bearing capacity. These cracks affect the integrity and stability of the foundation wall itself. If ignored, they will almost certainly get worse, compromising your home’s safety and value, often leading to costly issues like bowing walls or significant differential settlement.

Causes of Structural Cracks:

Differential Settlement: This is a major issue where the foundation settles unevenly. It happens when one section of the soil beneath the foundation is weaker or wetter than another, causing the foundation to sink at different rates and putting immense stress on the structure above.
Expansive or Swollen Soil: When certain types of soil (like clay) absorb large amounts of water (from heavy rains or improper grading), they expand or swell. This expansion exerts enormous lateral (sideways) pressure on the foundation walls, often resulting in severe horizontal cracks.
Poor Soil Bearing: This occurs if the soil was not adequately compacted or if the existing soil composition simply cannot properly support the structure’s massive weight, leading to failure and movement.
Overloading: When excessive weight is placed on the foundation, such as adding a second or third storey without adequate structural reinforcement, it can exceed the load-bearing capacity of the original foundation.
Frost Heave (A Toronto Concern!): When soil moisture freezes, it expands and pushes upward. If the foundation footing isn’t placed deep enough (below the frost line), the expanding frozen soil can lift the foundation unevenly, causing severe stress and cracking.
Construction Issues: Structural failure can sometimes be traced back to poor construction practices, such as inadequate steel reinforcement in the concrete or using substandard materials during the build.

How to Identify Structural vs. Non-Structural Cracks

When you are assessing a crack in your foundation wall, the visual characteristics – their size, shape, and pattern – are your best clues. Always monitor the crack over several months to see if it changes. Here’s what to look for to determine if you have a cosmetic issue or a serious structural problem:

Signs of a Non-Structural Crack (The Common Kind)

These cracks are usually harmless to your home’s stability, but still need sealing to prevent leaks.

Size: They are typically hairline cracks and measure no more than 1/8 inch wide. This is roughly the thickness of a typical coin, like a nickel.
Pattern: They are most often vertical cracks that run straight up and down, from the top of the wall down to the floor. In poured concrete foundations, a single vertical crack is a classic sign of concrete shrinkage.
Stability: A key indicator is that they generally remain the same size over time. They don’t show visible changes in width, length, or direction after months or even years.
Location: You might see them isolated to just one block in a concrete block wall, or they may appear near door or window corners in drywall or plaster, often in a straight line, resulting from minor framing shifts.
Appearance: They are frequently called Shrinkage Cracks because they occur as the concrete dries and shrinks, making them common in newly built homes.

Signs of a Structural Crack (The Serious Kind)

These patterns indicate that the soil is moving or the foundation is stressed. If you see any of these signs, contact DGI Waterproofing immediately for a professional inspection.

Size: They are generally wider than 1/8 inch (wider than a coin) and often exhibit a distinct characteristic: they may be wider at one end than the other, which is a telltale sign of differential settlement.
Pattern: Look for these serious patterns:

Horizontal Cracks: These run parallel to the ground in foundation walls and are almost always structural. They are typically caused by massive pressure from swelling soil or frost heave pushing the wall inward.
Stair-Step Cracks: These are common in concrete block or brick walls where the crack follows the mortar joints in a zigzag or stair-step pattern. This is a definitive sign of severe settlement or soil movement.

Large Diagonal Cracks: Cracks running at a steep angle (45-75 degrees) often indicate that one part of the foundation is sinking faster than the rest.
A Series of Vertical Cracks: A grouping of multiple vertical cracks close to each other suggests a broader structural problem, not just localized shrinkage.
Location:

Cracks that extend through multiple levels of the home (e.g., from the basement foundation up into the main floor walls).
Cracks that run across a ceiling and down an interior wall.

Movement: The most critical sign is that the crack is visibly growing larger or changing in width, length, or direction over time. You can monitor this by marking the ends of the crack with a pencil or placing a small piece of clear tape across it to see if the tape tears.

Repair Strategies: Solutions by DGI Waterproofing

The repair method depends entirely on the type and cause of the crack. As experts, DGI Waterproofing offers crack repair as part of our basement waterproofing services, ensuring a permanent fix, providing security and a long-term transferable warranty on many of our wall crack repairs.

Non-Structural Crack Repair: Sealing and Preventing Leaks

Since these cracks don’t require structural reinforcement, the focus is on sealing them to prevent water infiltration and the damaging freeze/thaw cycle.

Epoxy Injection: A low-cost, non-invasive method where an epoxy resin is injected into the crack. The resin hardens, creating a strong bond with the concrete and effectively sealing the crack against water.
Sealant: For wet non-structural cracks (those actively leaking), a flexible polyurethane foam is injected. It expands to fill the crack and create a flexible, effective, and long-lasting waterproof seal.

Structural Crack Repair: Stabilization and Reinforcement

These complex repairs require specialized engineering solutions to reinforce the wall and address the underlying cause of the foundation movement.

Carbon Fibre Reinforcement: High-strength carbon fibre straps are applied to the wall using a specialized adhesive. Once cured, they provide tremendous support and stability, preventing further cracking and bowing.
Wall Plate Anchors: Used to reinforce and prevent foundation walls from bowing or leaning inward. These anchors transfer the wall’s weight to a reinforced soil bed outside the foundation, providing stability.
Epoxy Injection with Stabilization: For structural cracks, epoxy is often combined with carbon fibre straps or metal pins inserted across the crack (like stitching) to permanently weld the concrete together, making the repaired area stronger than the original concrete.
Foundation Piers (For Settlement): For cracks caused by differential settlement, we drive push piers or helical piers deep into stable soil strata beneath the foundation. This stabilizes and can even lift the foundation back to its original position.
Exterior Drainage Systems: For extensive cracks and leaks caused by severe hydrostatic pressure or moisture issues, we might recommend an exterior weeping tile drainage system or French drain to redirect water away from the foundation.

Why Quick Crack Repair is Crucial for Homeowners

You might think that if a crack isn’t structural, it can be ignored. Wrong. Even the smallest non-structural crack can lead to serious, costly issues.

The Problem: Water Infiltration and Foundation Leaks

The biggest threat from any unsealed crack – structural or non-structural – is water penetration.

Basement Flooding & Damage: A foundation crack is a direct pathway for water to enter your basement, potentially damaging carpets, furniture, and electronics.
Mould and Mildew: Persistent moisture leads to the growth of mould, creating an unhealthy living environment that can affect air quality and cause respiratory issues. Over time, this will necessitate professional mould removal services.
Worsening Cracks (The Freeze/Thaw Cycle): This is especially important in Toronto. Water seeps into the crack, freezes during the winter, and expands. This process, known as the freeze/thaw cycle, turns a minor crack into a major problem, often widening non-structural cracks into serious ones over time.
Compromised Structural Integrity: For structural cracks, the longer you wait, the worse the soil movement becomes, leading to bowing walls and eventual foundation failure – requiring exponentially more expensive repairs.

Don’t Guess, Call the Toronto Experts

If you are seeing any crack- especially one that is wide, horizontal, or stair-stepping – do not attempt to fix it with a DIY solution. An improper fix can mask a serious underlying structural issue.

At DGI Waterproofing, we believe a strong foundation is the cornerstone of your home’s safety and value. We conduct thorough, professional assessments right here in Toronto to accurately identify the root cause of the crack, whether it stems from soil movement, water infiltration, or structural shifts.

Trust our certified waterproofing contractors to provide the tailored, warrantied solution you need for long-term protection and peace of mind.