Are Foundation Cracks Dangerous?

Foundation cracks are a common concern for homeowners in Toronto and the GTA. The region’s climate—with its cycles of rain, snow, freezing, and thawing—places significant stress on foundations, leading to cracking over time. While not all cracks pose an immediate threat, they can often signal underlying issues that, if left unaddressed, may compromise your home’s structural integrity and lead to basement water leaks.

In Toronto’s older housing stock, foundation cracks are particularly prevalent due to aging materials and construction methods. Even minor cracks can allow water to seep into your basement, causing dampness, mold, and costly water damage. Understanding the types of foundation cracks and their potential implications is the first step in protecting your home.

Types of Foundation Cracks and Their Risks

While not all foundation cracks are dangerous, some can indicate serious problems. Here’s what you need to know about the types of cracks and their causes:

  • Horizontal Cracks: Often caused by lateral pressure from soil or water pressing against the foundation walls, horizontal cracks can signal serious structural stress. If left unchecked, they may lead to wall bowing or collapse.
  • Vertical Cracks: These are usually caused by normal settling of the foundation or shrinkage of concrete during curing. While not always serious, vertical cracks that widen over time or allow water infiltration should be inspected.
  • Diagonal Cracks: These often appear due to uneven settling or shifting of the foundation. They can indicate that one side of your home is sinking, which may require immediate attention.
  • Hairline Cracks: Common in new homes, hairline cracks typically result from curing concrete. These are often superficial but should still be monitored for changes.

While some cracks are benign, others can result from serious issues such as soil subsidence, water pressure, or structural movement. Regular inspection is key to determining whether cracks require repairs or further investigation.

Foundations Move and Shift Over Time

Foundations naturally move and shift over time due to a variety of environmental and structural factors. While some movement is normal and may not pose immediate risks, excessive shifting can lead to cracks, uneven floors, and structural instability. Below, we dive deeper into the primary reasons why foundations move and shift, with a focus on issues common in Toronto and the GTA.

1. Soil Expansion and Contraction

One of the most significant causes of foundation movement is the expansion and contraction of the soil beneath it. This is particularly relevant in Toronto, where clay-heavy soils dominate. Clay soils are highly expansive, meaning they absorb water during wet periods (causing them to swell) and lose moisture during dry periods (causing them to shrink). This constant cycle of swelling and shrinking creates pressure on the foundation, leading to cracks and shifting.

  • Freeze-Thaw Cycles: Toronto’s cold winters exacerbate this issue. When water in the soil freezes, it expands, creating upward pressure on the foundation. When the ice thaws, the soil contracts, leaving gaps that can destabilize the foundation.
  • Water Saturation: Poor drainage systems can cause soil around the foundation to become oversaturated, increasing the risk of soil movement and settlement.

2. Natural Settling of the Foundation

All homes experience some degree of natural settling after construction as the soil beneath the foundation compacts under the weight of the structure. While this process is normal and usually minor, uneven settling can occur if the soil is poorly compacted, leading to differential settlement. This uneven movement can result in diagonal or vertical cracks and uneven floors.

  • Improper Soil Preparation: Homes built on improperly compacted soil or fill are more prone to uneven settlement, as the ground beneath them continues to compress over time.
  • Expansive Soils: Homes built on expansive soils, common in the GTA, often experience more pronounced settlement issues due to the soil’s movement when wet or dry.

3. Water Drainage Issues

Water is one of the biggest threats to a foundation’s stability. When water isn’t properly routed away from the home, it can saturate the soil surrounding the foundation, leading to erosion, instability, and movement. Common water drainage issues include:

  • Poor Grading: If the landscaping around your home slopes toward the foundation rather than away from it, water can pool around the base of the home, destabilizing the soil.
  • Clogged or Missing Gutters: When gutters are clogged or downspouts don’t extend far enough, rainwater can flow directly down to the foundation, contributing to erosion and water saturation.

4. Seasonal and Environmental Factors

Toronto’s weather patterns and environmental conditions contribute significantly to foundation movement. For example:

  • Heavy Rainfall: Frequent rainstorms in Toronto can saturate the soil, creating hydrostatic pressure on the foundation walls. This pressure can push the walls inward, causing cracks and shifts.
  • Drought: Conversely, long dry spells can cause the soil to shrink and pull away from the foundation, leading to gaps and uneven support.

5. Tree Roots and Vegetation

The presence of large trees or shrubs near the foundation can also contribute to movement. Tree roots can extend far beyond the canopy and grow toward sources of moisture, such as the soil beneath your foundation. As roots grow and expand, they can disturb the soil, creating uneven pressure that leads to foundation shifting.

  • Moisture Absorption: Trees and plants absorb moisture from the soil, which can exacerbate soil shrinkage during dry periods, causing the foundation to settle unevenly.
  • Physical Damage: In some cases, roots can grow into the foundation itself, causing cracks and other damage.

6. Aging of Materials

Over time, the materials used in constructing a home’s foundation—such as concrete and mortar—can degrade. Cracks may form as the materials shrink, settle, or become less cohesive. In older homes, this process can be more pronounced, as early construction methods often relied on friction and gravity to hold structures in place rather than modern reinforcement techniques.

  • Older Construction Methods: Many homes in Toronto’s older neighborhoods were built without reinforced foundations, making them more susceptible to shifting over time.
  • Wear and Tear: Exposure to fluctuating temperatures, moisture, and other environmental factors accelerates the aging process of foundation materials.

7. Vibrations and External Forces

External factors, such as nearby construction, heavy vehicle traffic, or even natural seismic activity, can cause vibrations that disturb the soil beneath a foundation. These forces can lead to small shifts that, over time, accumulate and cause visible damage.

Inspecting For Foundation Cracks

You can perform a preliminary inspection of your foundation cracks using these tips:

  1. Measure the Crack: Use a ruler to measure the width of the crack. Cracks wider than 1/4 inch or that appear to be expanding over time should be inspected by a professional.
  2. Determine the Shape: V-shaped cracks can indicate pressure from below (such as soil expansion), while cracks wider at the bottom may suggest downward pressure from soil subsidence.
  3. Check for Water Infiltration: Look for signs of dampness or water stains near the crack. Even small cracks can allow water to enter your basement.
  4. Test Floor Levels: Use a marble to check for uneven floors. Movement in multiple directions is a sign that the foundation is shifting unevenly.

For a thorough assessment, it’s always best to consult a professional with experience in structural repairs and foundation waterproofing.

Downward Pressure

A downward force will create a vertical crack which is wider at the bottom than the top and the force often originates from subsidence of the soil located below the building’s foundation. A structure can also be damaged by outward or inward force. Horizontal cracks usually aren’t serious, but if the surface below or above the crack has been forced outward or inward there could be problems. Inward or outward pressure can be the result of improper backfill, pressure of moving water and earth, or vehicle traffic that is too close to the foundation.

If you can determine the direction and lace of the force which has caused the cracks then it’ll be easier to find the source. If the damage is hidden though, it can be very hard to determine and costly to repair as floors, ceilings and walls may need to be opened to reveal the damage. It’s also possible you won’t realize there’s any damage until the structure eventually fails.

Repair and Prevention Options for Foundation Cracks

Addressing foundation cracks early can prevent costly damage down the line. Here are some common repair and prevention methods:

  • Crack Injection: Epoxy or polyurethane injection is a common method for sealing small cracks and preventing water infiltration.
  • Waterproofing Solutions: Installing or upgrading exterior or interior waterproofing systems, such as weeping tiles or sump pumps, helps prevent water from saturating the soil around the foundation.
  • Foundation Reinforcement: For larger cracks or structural concerns, reinforcement methods such as carbon fiber strips or underpinning can stabilize and strengthen the foundation.
  • Improved Drainage: Ensuring proper grading, adding downspout extensions, or installing French drains can direct water away from your foundation, reducing pressure and preventing future cracks.

Foundation Tips When Buying a Home

When buying a home, it’s recommended that you inspect the patios, driveways and sidewalks to see if they’re sunken, heaved, cracked or twisted. If they are then the property may have expansive soils. If the foundation and other structures have been built for the conditions and water is routed away from concrete pads and the foundation you should find little indication of any concrete damage. Remember that most homes erected on expansive soils generally show some defects due to the constant expansion and contraction of the earth. It’s a good idea to have your home inspected if you’re unsure of any damage or contract a structural engineer for a professional opinion.

Have a questions about a crack in your foundation?  Nusite Waterproofing serves Toronto and the surrounding GTA.  We offer a free in-home inspection and estimate and can advise on how to repair your foundation crack.  Contact us here today to schedule an appointment.