If you’ve noticed your interlock pavers aren’t quite level anymore, you’re likely dealing with one of two common issues: heaving or settling. While both problems result in an uneven surface, they have completely different causes, warning signs, and solutions. Understanding which issue you’re facing is crucial for choosing the right repair approach and preventing future problems.

In Ottawa’s harsh climate, where temperatures can swing from -30°C in winter to +30°C in summer, both heaving and settling are unfortunately common. Let’s explore how to identify which problem you’re dealing with and what you can do about it.

What Is Heaving?

Heaving occurs when the ground beneath your pavers expands upward, pushing sections of your interlock surface higher than the surrounding area. This is almost exclusively a winter phenomenon caused by frost action in the soil.

The Science Behind Frost Heaving

When water in the soil freezes, it expands by approximately 9%. In Ottawa’s freeze-thaw climate, this process happens repeatedly throughout the winter months. As temperatures drop, moisture in the soil freezes and expands, creating ice lenses that push the soil—and everything above it—upward. When temperatures rise, the ice melts, but the soil doesn’t always settle back to its original position.

This cycle of freezing and thawing is particularly aggressive in Ottawa. Our city experiences what’s known as the freeze-thaw zone, where temperatures regularly cross the freezing point throughout winter and spring. This makes heaving one of the most common issues homeowners face with their interlock installations.

Visual Signs of Heaving

Heaving has distinct characteristics that make it relatively easy to identify:

Seasonal Appearance: The problem appears or worsens during winter and early spring, often improving slightly when the ground thaws completely
Upward Movement: Sections of pavers are pushed upward, creating humps or raised areas rather than depressions
Edge and Corner Focus: Heaving typically affects the edges of your patio or driveway first, particularly areas near the perimeter or corners where frost penetration is greatest
Uniform Sections: Entire sections of pavers move together as a unit, maintaining their relationship to each other while lifting as a group
Crack Patterns: You may see cracks radiating outward from the heaved area as the surrounding pavers are stressed by the upward movement
Water Pooling Changes: Areas that previously drained well may now shed water toward the center or create new pooling patterns

Common Heaving Locations

In Ottawa properties, heaving most commonly occurs in these areas:

Northern exposures that receive less direct sunlight and stay frozen longer
Areas with poor drainage where water accumulates before freezing
Sections near downspouts or other water sources
Edges of installations where frost can penetrate from multiple angles
Thin installations with inadequate base depth below the frost line

What Is Settling?

Settling is the opposite problem—sections of your interlock pavers sink below the surrounding surface, creating depressions, dips, or sunken areas. Unlike heaving, settling is typically a year-round issue related to base failure or soil compaction problems.

The Mechanics of Settling

Settling occurs when the base materials beneath your pavers compress, shift, or wash away, leaving voids that cause the surface to sink. This can happen for several reasons:

Inadequate Compaction: If the base wasn’t properly compacted during installation, it will continue to compress under traffic and weather exposure
Base Erosion: Water infiltration can wash away sand and aggregate base materials, creating voids beneath the pavers
Organic Soil Decomposition: If the installation was placed over topsoil or organic material, decomposition creates settling as the material breaks down
Heavy Load Stress: Regular traffic from vehicles, particularly heavier ones, can compress base materials over time
Poor Drainage Design: Water accumulation saturates base materials, reducing their load-bearing capacity and causing compression

Visual Signs of Settling

Settling presents different visual cues than heaving:

Year-Round Presence: Unlike heaving, settling doesn’t follow seasonal patterns—it persists regardless of temperature
Downward Movement: Pavers sink below the surrounding surface, creating depressions, dips, or “birdbath” areas where water pools
Traffic Pattern Correlation: Settling often follows traffic patterns, appearing in wheel tracks on driveways or high-traffic walkway areas
Progressive Worsening: The problem gradually gets worse over time as more base material compresses or erodes
Individual Paver Movement: Individual pavers may rock or shift when stepped on, unlike the solid, unified movement of heaved sections
Separation and Gaps: Joint sand disappears more quickly in settled areas, and gaps between pavers may widen
Water Accumulation: Settled areas become collection points for water, which can accelerate the problem by washing away more base material

Common Settling Locations

Settling typically appears in these problem areas:

Driveway approach areas where vehicles brake and accelerate
Vehicle turning areas where twisting forces stress the base
Low spots in the yard where water naturally accumulates
Areas near irrigation systems or downspouts
Sections installed over poorly compacted fill soil
High-traffic walkway zones

Ottawa Climate Factors: Why Both Problems Are Common Here

Ottawa’s unique climate creates the perfect storm for both heaving and settling issues. Understanding these factors helps explain why interlock maintenance is so important in our region.

The Freeze-Thaw Cycle

Ottawa experiences one of the most aggressive freeze-thaw cycles in Canada. Our winters see temperatures that regularly cross the 0°C threshold—sometimes multiple times in a single week during spring and fall. This constant freezing and thawing is particularly destructive to interlock installations.

Each freeze-thaw cycle weakens the base materials, creates expansion and contraction stress, and promotes both heaving and settling. Water that infiltrates the base freezes and expands, then melts and flows, carrying base materials with it. Over years, this cycling causes significant cumulative damage.

Deep Frost Penetration

The Ottawa region requires foundations to extend 4 feet (1.2 meters) below grade due to our deep frost line. This same frost penetration affects interlock installations. Any base that doesn’t extend well below the frost line is vulnerable to heaving as freezing temperatures reach the soil beneath.

Heavy Spring Runoff

Our significant winter snowfall creates heavy spring runoff periods. When all that accumulated snow melts in a relatively short time frame, the resulting water flow can wash away base materials, erode edges, and saturate the ground—contributing to settling issues just as heaving begins to subside.

Clay Soil Composition

Many Ottawa properties have clay-heavy soil, which presents unique challenges. Clay holds water, expands when wet, shrinks when dry, and is highly susceptible to frost heaving. This soil type makes proper base installation and drainage even more critical than in areas with sandy or gravelly soil.

How to Diagnose Your Specific Problem

Now that you understand both issues, here’s how to determine which one you’re facing:

The Seasonal Test

Monitor your pavers through different seasons. Take photos of problem areas in winter, spring, summer, and fall. If the issue appears or worsens in winter and spring but improves in summer, you’re likely dealing with heaving. If the problem remains constant or gradually worsens regardless of season, settling is the culprit.

The Direction Test

Simply observe whether affected areas are raised above or sunken below the surrounding surface. Heaving pushes upward, while settling sinks downward. This might seem obvious, but the distinction is crucial for repair planning.

The Water Test

Pour water on the affected area and watch where it flows. Heaved areas shed water outward toward the surrounding surface. Settled areas collect water, creating puddles that persist after rain.

The Timing Test

Consider when you first noticed the problem. Did it appear suddenly after a harsh winter? That suggests heaving. Has it developed gradually over multiple seasons? That points to settling.

Solutions for Heaving

Addressing heaving requires tackling the root cause: frost penetration and water accumulation in the base.

Immediate Solutions

For minor heaving, you can implement temporary fixes:

Wait until spring for the ground to fully thaw, then monitor if the problem self-corrects
Remove and reset affected pavers once the ground has completely thawed
Improve surface drainage to prevent water from reaching the base layer

Permanent Solutions

For recurring or severe heaving, more comprehensive repairs are necessary:

Base Depth Improvement: Excavate and install a deeper base that extends below the frost line (4+ feet in Ottawa)
Base Material Upgrade: Replace the base with non-frost-susceptible materials like clear stone or crushed granite
Drainage System Installation: Add perimeter drainage or subsurface drains to prevent water accumulation
Edge Restraint Enhancement: Install proper edge restraints to contain the pavers and resist frost forces
Insulation Addition: In extreme cases, adding rigid insulation below the base can prevent frost penetration

Professional interlock repair services can assess the severity of heaving and recommend the most cost-effective solution for your specific situation.

Solutions for Settling

Settling repairs focus on restoring and improving the base structure beneath your pavers.

Minor Settling Repairs

For small, isolated settled areas:

Remove pavers from the affected section
Add and compact new base material to restore proper elevation
Reset pavers and resand joints
Address any drainage issues that contributed to base erosion

Major Settling Repairs

For extensive or recurring settling, more significant intervention is required:

Complete Base Reconstruction: Remove all pavers, excavate and replace the failed base with properly compacted materials
Soil Stabilization: If settling is due to soft underlying soil, soil stabilization techniques may be necessary
Drainage Correction: Install proper drainage systems to prevent water from saturating and eroding base materials
Base Depth Increase: Provide adequate base depth for the intended use (4-6 inches for walkways, 8-12 inches for driveways)
Geotextile Fabric: Install fabric between subgrade and base to prevent mixing and migration of materials

For comprehensive solutions to sunken pavers, explore our guide on sunken interlock causes and fixes.

When to Consider Complete Relaying

Sometimes, repairs aren’t enough. Consider complete interlock relaying if:

More than 30% of your surface is affected
The original installation used inadequate base depth or materials
You’re experiencing both heaving and settling in different areas
Previous repairs have failed to solve the problem
The installation is more than 15-20 years old and showing multiple issues

Prevention: Avoiding Future Problems

Whether you’re dealing with heaving or settling, prevention strategies can minimize future issues:

Proper Installation Is Key

The best prevention is proper installation from the start:

Adequate base depth for Ottawa’s climate (minimum 12 inches for driveways)
Proper compaction in lifts no greater than 4 inches
Use of appropriate base materials (clear stone, not sand or soil)
Geotextile fabric to separate subgrade from base
Solid edge restraints to contain the system
Proper slope for drainage (minimum 2% grade away from structures)

Regular Maintenance

Ongoing maintenance helps catch small problems before they become major issues:

Annual joint sand replenishment to maintain paver stability
Regular cleaning to prevent organic buildup and drainage blockage
Prompt repair of any individual settled or shifted pavers
Monitoring and maintaining proper drainage around the installation
Winter inspection for heaving signs after major freeze-thaw events

Drainage Management

Proper water management is crucial for preventing both heaving and settling:

Ensure downspouts discharge well away from interlock surfaces
Maintain proper surface slope throughout the installation
Keep joint sand filled to allow water to drain through rather than around pavers
Consider perimeter drainage systems in problem areas
Prevent irrigation overspray onto paved areas

When to Call the Professionals

While some minor repairs can be DIY projects, professional assessment is recommended when:

You’re uncertain whether you’re dealing with heaving or settling
The affected area is larger than a few square feet
The problem has recurred after previous repair attempts
You need to ensure proper base depth and materials for Ottawa’s climate
The installation is near your home’s foundation or other critical structures
You want warranty protection on the repair work

Professional contractors have the equipment, materials, and expertise to properly diagnose the root cause and implement lasting solutions that address Ottawa’s unique climate challenges.

Understanding Costs: Repair vs. Replace

The cost of addressing heaving or settling varies widely based on the extent of the problem:

Minor repairs (small settled or heaved sections) typically cost $500-$1,500, depending on the area size and accessibility.

Major repairs (significant base reconstruction) can range from $2,000-$5,000 or more, depending on the size of the affected area and the extent of base work required.

Complete relaying is often the most cost-effective solution when damage is extensive, typically costing 60-70% of new installation prices but providing a completely restored surface with proper base construction.

When evaluating costs, consider the long-term value of proper repairs versus repeated band-aid fixes that don’t address the root cause.

Conclusion: Different Problems Require Different Solutions

While both heaving and settling result in uneven interlock surfaces, they’re fundamentally different problems requiring distinct solutions. Heaving is a seasonal issue driven by frost action and requires improved drainage and base depth below the frost line. Settling is typically a year-round problem caused by base failure and requires base reconstruction and compaction.

Understanding which issue you’re facing—or whether you’re dealing with both in different areas—is the first step toward implementing the right solution. In Ottawa’s challenging climate, both problems are common, but both are also solvable with proper diagnosis and repair techniques.

If you’re unsure which problem you’re facing or need expert assessment of your interlock surfaces, professional evaluation can save you time and money by ensuring the right solution is implemented the first time.

Get Expert Help for Your Interlock Issues

Don’t let heaving or settling damage compromise your property’s appearance and value. Whether you need minor repairs or complete base reconstruction, Interlock Experts has the experience and expertise to restore your surfaces to like-new condition.

Our team understands Ottawa’s unique climate challenges and uses proven techniques to address both heaving and settling issues with lasting results. We provide comprehensive assessments, transparent pricing, and warranty-backed repairs that stand up to our harsh winters.

Contact Interlock Experts today for a free assessment of your heaving or settling issues. We’ll diagnose the problem, explain your options, and provide a detailed quote for permanent solutions.

Heaving vs Settling: How to Tell What’s Happening to Your Pavers