Did my Ottawa interlock base settle or did the pavers shift on their own?

Interlock pavers don't shift on their own — what you're seeing is almost certainly base settlement beneath the pavers. Concrete pavers are heavy, stable units that stay put when properly supported, but they'll follow any movement in the base layers below.

Base settlement is extremely common in Ottawa interlock driveways, especially those installed in the last 10-15 years when many contractors cut corners on base depth to stay competitive. Ottawa's deep frost line (1.2 to 1.5 metres) and expansive clay soils create challenging conditions that demand proper base preparation. When the granular base is too shallow or inadequately compacted, freeze-thaw cycles and heavy snow loads cause the base to shift, settle, and heave — taking the pavers along for the ride.

The telltale signs of base settlement versus surface issues are easy to spot. If you see sunken areas where pavers have dropped below the surrounding level, gaps opening between pavers, or sections that rock when you step on them, that's base settlement. You might also notice that the settled areas correspond to wheel tracks where vehicles repeatedly load the driveway, or areas where water pools after rain. Surface-only problems would show as individual loose pavers or damaged units, not coordinated movement of entire sections.

Ottawa's clay soils are particularly problematic for interlock bases. Clay expands when wet and shrinks when dry, creating unstable subgrade conditions. Many Ottawa neighbourhoods — including much of Barrhaven, Orleans, Gloucester, and Riverside South — sit on clay that wasn't properly addressed during original installation. Without adequate granular base depth (minimum 450mm total in Ottawa) and geotextile fabric to separate clay from granular material, the base becomes contaminated with clay fines and loses its structural integrity.

Inadequate compaction during installation is another major culprit. Granular base must be compacted in 150mm lifts with proper equipment — not hand-tamped or single-pass compacted. Many budget installations skip proper compaction to save time, leaving voids in the base that compress under load and freeze-thaw cycling. The first few Ottawa winters reveal these shortcuts as pavers settle into the compressed base.

To confirm base settlement, look for these additional signs: water pooling in the settled areas (indicating the drainage slope has been compromised), polymeric sand washing out of joints around settled pavers, and edge restraints that have shifted or pulled away from the paver field. You might also notice that the settled areas feel soft or spongy when you walk on them, especially after rain.

Fixing base settlement requires lifting the affected pavers, addressing the underlying base problem, and relaying the surface. This typically involves excavating the settled area, adding and properly compacting granular base material, re-establishing proper drainage slope, and carefully relaying the pavers with fresh bedding sand and polymeric sand. It's not a DIY repair — proper base work requires understanding soil conditions, compaction techniques, and drainage principles.

The good news is that interlock pavers themselves are rarely damaged by base settlement — they can usually be lifted, the base repaired, and the same pavers relaid. This is one advantage of interlock over asphalt, where base failure requires complete removal and replacement of the surface.

Need help finding a qualified interlock contractor to assess and repair your base settlement? Ottawa Driveways can match you with local paving professionals who understand Ottawa's challenging soil and climate conditions.