Why Interlock Driveways Sink (And How to Prevent It in Ottawa)

If your interlock driveway or patio is starting to sink or become uneven, you’re not alone.

This is one of the most common issues homeowners face in the Ottawa region.

The good news?

It’s preventable—and often repairable.

The Real Reason Interlock Fails

Most people think the problem is the stones.

In reality:

Interlock problems are almost always caused by what’s underneath.

1. Poor Base Preparation

A proper base should include:

• Deep excavation

• Compacted crushed stone

• Proper layering

If shortcuts were taken, the base will settle over time.

2. Clay Soil Movement

Ottawa-area soils often contain clay.

Clay:

• Expands when wet

• Shrinks when dry

This movement causes the base to shift, leading to uneven pavers.

3. Water Trapped Under the Base

Water is the biggest enemy of interlock.

If it cannot escape:

• It weakens the base

• Freezes and expands in winter

• Causes sinking and heaving

4. Lack of Proper Drainage

Many installations fail because water has nowhere to go.

A properly built system includes:

• surface slope

• base slope

• drainage path at edges

How to Prevent Interlock from Sinking

A long-lasting installation requires:

• Proper excavation depth

• Compacted aggregate base

• Geotextile fabric (in clay soils)

• Correct slope (away from house)

• Drainage edge or relief trench

These steps dramatically increase lifespan.

Can It Be Fixed?

Yes—most sinking interlock can be repaired by:

• lifting affected areas

• rebuilding the base

• reinstalling pavers

Done properly, repairs can last decades.

Final Thought

If your interlock is sinking, the issue won’t fix itself.

But addressing it early can save significant money and extend the life of your driveway or patio.

HIL specializes in interlock repair and proper base reconstruction.

If you’d like an assessment, contact us today.