Is Granular A or Granular B better for a driveway base in Ottawa and how thick should the gravel layer be?

Choosing the right granular base material is one of the most important decisions for a long-lasting Ottawa driveway. The base is what actually carries the load — the asphalt or pavers on top are just the wearing surface.

Granular A vs. Granular B — Key Differences

Granular A is a well-graded crushed limestone blend with particles ranging from stone dust up to 25 mm. It compacts into an extremely dense, stable layer and is the standard base material for driveways across Ottawa. Granular B is a coarser, more open-graded material with larger stones (up to 50 mm) and fewer fines. It provides excellent drainage but less surface stability on its own.

The Ideal Ottawa Driveway Base System

For most Ottawa properties, the best approach uses both materials in layers. The standard specification is:

• 150 mm (6 inches) of Granular B as the sub-base, placed directly on the prepared subgrade
• 150 mm (6 inches) of Granular A as the upper base course
• Each layer machine-compacted to 98% Standard Proctor density

This two-layer system gives you the drainage benefits of Granular B below with the tight, stable surface of Granular A on top. In areas with particularly poor soil — common in Orleans, Gloucester, and south Nepean where marine clay is prevalent — your contractor may recommend increasing the total base depth to 400 mm or more.

Why Base Depth Matters in Ottawa

Ottawa's frost penetration reaches 1.2 to 1.5 metres in a typical winter. While you cannot practically build a base that deep for a residential driveway, a properly thick granular base helps manage frost heave by providing a stable, free-draining layer that reduces ice lens formation. Skimping on base thickness is the single most common reason Ottawa driveways fail within the first five years.

Cost Expectations

In the Ottawa market, Granular A typically runs $25 to $35 per tonne delivered, and Granular B is slightly less at $20 to $30 per tonne. A standard two-car driveway (roughly 45 square metres) needs approximately 25 to 30 tonnes of combined granular material. Including delivery and machine compaction, budget $1,200 to $2,000 for base preparation alone — and be wary of any quote that seems to skip or minimise this cost.

Existing Base Assessment

If you are resurfacing an existing driveway, a good contractor will evaluate whether the current base is salvageable. In many Kanata and Stittsville subdivisions built in the 1990s, the original base was adequate and may only need spot repairs and re-grading before new asphalt goes down, saving significant cost.

Reach out through Ottawa Driveways to connect with a local paving contractor who can assess your specific base conditions and recommend the right granular specification.

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

• Homeupgraders
• JC Carpentry
• Vanguard Environmental
• Eastern Residential Solution
• Dreamwood Construction & Renovations

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