Why is my Ottawa driveway pulling away from the garage threshold?

Your driveway is pulling away from the garage threshold due to settling of the driveway base or frost heaving, both extremely common issues in Ottawa's harsh freeze-thaw climate. This gap typically develops when the driveway settles downward while the garage foundation (built on deeper footings below the frost line) remains stable.

The most likely cause is inadequate base preparation when your driveway was originally installed. Ottawa's frost line extends 1.2 to 1.5 metres deep, requiring substantial granular base depth to prevent frost heaving and settling. Many driveways, especially builder-grade installations, use only 150-200mm of base material when Ottawa conditions demand a minimum of 450mm total (300mm Granular B sub-base plus 150mm Granular A base). When water penetrates this insufficient base and freezes, it pushes the driveway upward in winter, then allows settling in spring as the ground thaws and compacts.

Clay soil conditions prevalent across much of Ottawa (Barrhaven, Orleans, Gloucester, Riverside South) make this problem worse. Ottawa clay expands dramatically when wet and shrinks when dry, creating unstable subgrade that causes differential movement between your garage foundation and driveway. The garage sits on concrete footings extending below the frost line, so it doesn't move. Your driveway, sitting on a shallower base, rises and falls with freeze-thaw cycles and clay movement.

Poor drainage around the garage threshold accelerates the problem. Water pooling against the garage allows more freeze-thaw penetration into the driveway base. Ottawa's 50+ freeze-thaw cycles per winter, combined with heavy snow loads and repeated plowing, stress the driveway-to-foundation connection relentlessly. Each cycle widens the gap slightly until you have a noticeable separation.

Immediate steps: Clean debris from the gap and inspect for water pooling during rain or snowmelt. Ensure your gutters direct water away from this area and that the driveway slopes away from the garage (minimum 2% grade). For a temporary fix, use polyurethane caulk rated for exterior concrete joints to seal gaps up to 25mm wide.

Permanent solutions depend on the extent of settling. If the gap is under 25mm and the driveway surface is otherwise stable, a concrete contractor can mud-jack (pressure-inject concrete slurry) beneath the settled section to raise it back to the original level, then seal the joint properly. Cost: $800 to $2,000 depending on area affected.

If the gap exceeds 25mm or the driveway shows widespread cracking and settling, the base has likely failed and requires full reconstruction of the affected section. This involves excavating the settled area, installing proper base depth with geotextile fabric over clay subgrade, and rebuilding with new asphalt, concrete, or interlock. Cost: $2,000 to $6,000 depending on size and material choice.

When to hire a pro: Any gap wider than 12mm indicates significant base movement requiring professional assessment. A qualified paving contractor can determine whether the foundation is stable, assess base conditions, and recommend repair versus replacement. Don't ignore this issue — water entering the gap can undermine your garage foundation and create ice buildup that damages both surfaces.

Find llocal paving contractors through the Ottawa Construction Network to get multiple opinions on the best repair approach for your specific situation.