Should I use 7/8 crusher run or 3/4 clear for my Ottawa base?

For Ottawa driveways, you want 3/4" clear stone (Granular A) as your top base layer, not 7/8" crusher run. The 3/4" clear provides better compaction and drainage, which are critical for surviving Ottawa's brutal freeze-thaw cycles.

Here's the proper Ottawa driveway base specification: Start with Granular B sub-base (crusher run with fines, typically 4" down to dust) as your primary structural layer — minimum 300mm (12") compacted depth due to Ottawa's deep frost line of 1.2 to 1.5 metres. This coarse material with fines compacts into a solid, stable foundation that won't shift during frost heaving.

On top of the Granular B, place Granular A base (3/4" clear stone) in a minimum 150mm (6") compacted lift. The 3/4" clear stone is angular crushed limestone with minimal fines, allowing excellent drainage while providing a smooth, stable surface for asphalt paving. The angular edges lock together under compaction, creating a firm platform that won't rut under the paving equipment.

Why 3/4" clear beats crusher run for the top base layer: Crusher run contains too many fines (dust and small particles) for the final base layer. While fines help with compaction in the sub-base, they reduce drainage in the top layer and can create a "muddy" surface when wet that's difficult to pave over. The 3/4" clear stone drains freely, preventing water from pooling at the asphalt interface where freeze-thaw damage starts.

Ottawa-specific considerations: Our clay soils in areas like Barrhaven, Orleans, and Gloucester make proper drainage even more critical. Clay expands when wet and contracts when dry, so any water trapped in the base system will cause movement and cracking. The 3/4" clear allows water to drain down into the Granular B layer and away from the driveway structure.

Compaction is crucial — both layers must be compacted in 150mm lifts with a plate compactor or vibratory roller. Hand tamping or single-pass compaction won't achieve the 95% compaction density needed to prevent settling during Ottawa's spring thaw.

When to hire a pro: Base preparation requires precise depth measurement, proper compaction equipment, and understanding of drainage slopes. A poorly prepared base is invisible once paved but will cause catastrophic failure within 3-5 Ottawa winters, requiring expensive tear-out and replacement.

Need help finding a qualified paving contractor who understands Ottawa base specifications? Ottawa Driveways can match you with experienced local professionals who know how to build driveways that survive our extreme climate.