Can a granular layer under the footing replace drain tile in Ontario?

Yes, Ontario's Building Code provides an alternative to drain tile at the base of the foundation wall. Instead of perforated pipe surrounded by stone, clause 9.14.4.2 allows a granular layer at least 125 mm deep placed under the footing and extending at least 300 mm beyond its outside edge.

The standard approach under clause 9.14.3.2 and 9.14.3.3 calls for drain tile or pipe at least 100 mm in diameter, with butt joints left 6 mm to 10 mm open, covered on the top and sides with at least 150 mm of crushed stone or other coarse clean granular material where no more than 10 per cent of the material passes a 4 mm sieve. The granular-layer alternative in 9.14.4.2 is a different path to the same goal: moving water away from the base of the wall.

A few things shape whether the alternative actually works for a given house:

• Clause 9.14.2.1 requires drainage at the bottom of every foundation wall that contains the building interior, unless it can be shown to be unnecessary. The granular layer is one way to meet that requirement, but it still has to drain somewhere. Clause 9.14.5.1 says foundation drains discharge to a sewer, a drainage ditch, or a dry well. A dry well is only permitted where natural groundwater is below its bottom and it sits at least 5 m from the foundation (9.14.5.3).
• Where hydrostatic pressure occurs, clause 9.13.3.1 requires waterproofing rather than dampproofing. The Code does not give a number or a test for when hydrostatic pressure occurs, so ask the contractor which protection the quote covers and why.

If someone is proposing the granular alternative as a retrofit, ask them to explain in writing exactly how it will drain and where that water goes.

The City of Ottawa's permit list names "structural foundation repairs and drain tile replacement" as work that requires a building permit. Make sure the written quote names the drainage method, the discharge point, and who applies for the permit.