What kind of gravel or stone base do I need under interlock pavers in Ottawa and how deep should it go?

The base system under interlocking pavers is what determines whether your Ottawa driveway stays level and beautiful or becomes a wavy, sunken mess within a few years. Our freeze-thaw conditions demand a more robust base than milder climates.

The Standard Ottawa Paver Base System

The Interlocking Concrete Pavement Institute (ICPI) guidelines, adapted for Ottawa's frost conditions, call for:

Total Excavation Depth

When you add it all up, a proper Ottawa interlock driveway requires excavation of 350 to 450 mm (14 to 18 inches) below the finished grade. This accounts for the full granular base, bedding sand, and paver thickness (typically 60 to 80 mm for driveway-rated pavers).

Why Ottawa Needs More Base Than the Minimum

ICPI's general recommendation for residential driveways is 6 inches of compacted base. That works in moderate climates, but Ottawa's frost penetration to 1.2-1.5 metres and our heavy clay subsoils mean the minimum is rarely enough. Most experienced Ottawa interlock contractors install 10 to 14 inches of total granular base as standard practice.

Gravel Types and Specifications

• Granular B (OPSS Type II): 50 mm max aggregate, open-graded, excellent drainage. Sourced from local quarries in the Ottawa Valley.
• Granular A (OPSS Type I): 25 mm max aggregate, well-graded with fines, compacts to a dense stable surface. The workhorse base material for Ottawa construction.
• HPB (High-Performance Bedding): Washed, angular crushed stone chips used as bedding sand. Superior to natural sand for bedding because it does not shift under load.

For a typical 500-square-foot interlock driveway in Ottawa, base material costs alone run roughly $1,500 to $2,500 including delivery, placement, and machine compaction. This represents about 30 to 40 percent of the total project cost — and it is the last place you want to cut corners.

Compaction Is Non-Negotiable

Every granular lift must be compacted to 98% Standard Proctor density using a plate compactor or roller. In Ottawa, compaction should be done in maximum 100 mm lifts. Dumping the full base depth and compacting once from the top is a common shortcut that leads to premature failure.

Connect with experienced interlock contractors through Ottawa Driveways to ensure your base is built to handle Ottawa's demanding climate conditions.

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Looking for experienced contractors? The Ottawa Construction Network connects Ottawa homeowners with qualified professionals:

• Homeupgraders
• RenoMotion Inc.
• Home Front Services
• Demontigny Carpentry
• Diamond renovations