Can waterproofing replace the drainage layer on an Ottawa foundation?

In one specific sense, yes. Ontario's Building Code calls for a drainage layer only where foundation-wall insulation extends more than 900 mm below the ground outside, and says that layer is not required where the wall is waterproofed. But the drainage layer is not the drain tile, and the wall still needs drainage at its base whether or not it is waterproofed.

What the drainage layer is

The drainage layer (9.14.2.1) is a layer against the outside of the foundation wall, such as mineral fibre insulation or free-draining granular material. The Code calls for it where foundation-wall insulation extends more than 900 mm below the ground outside. Where the wall is waterproofed, that layer is not required.

Separately, the Code requires drainage at the bottom of every foundation wall that contains the building interior, unless it can be shown to be unnecessary (9.14.2.1). That is the drain tile: at least 100 mm in diameter, its top below the bottom of the floor slab, covered on the top and sides with at least 150 mm of crushed stone or other clean coarse granular material (9.14.3.2, 9.14.3.3). Waterproofing the wall leaves that requirement in place.

Waterproofing itself is required where hydrostatic pressure occurs (9.13.3.1), and the Code gives no number for that. It must be continuous across joints and at junctions, and protected from damage during backfilling (9.13.3.4). Block walls get at least 6 mm of mortar parging coved over the footing first (9.13.3.3).

If a quote leaves out a drainage layer because the wall is being waterproofed, ask the contractor to put in writing:

• that the wall is being waterproofed, not dampproofed
• what happens to the drain tile at the footing, and where it drains
• how the membrane is protected during backfill

The one question to ask before signing is whether the quote names waterproofing or dampproofing, because only waterproofing removes the drainage-layer requirement.