This is the City of Markham’s document, as published on its website on 18 October 2026. The municipality may have changed it since: check the current version at the source. Legal notice
- Type
- Guide
- Published by
- City of Markham
- Date
- January 1, 2025
- For
- builder
- Building types
- All building types
- Pages
- 2
- Instruments
- CAN3-A93-M, Natural Airflow Ventilation for Buildings
Overview
The City of Markham's Builder Tip No. 71, dated January 1, 2025 and updated to the 2024 OBC, listed with its non-housing tips under the 2024 Ontario Building Code though it quotes Part 9: Article 9.19.1.1., Required Venting, Sentences 9.19.1.2.(2) to (5) on a 1/150 vent area for low-slope and joist roofs, 25% of vents at top and bottom, 38 mm cross purlins and CAN3-A93-M vents, and Article 9.19.1.3. on 63 mm clearance above insulation. Its objective applies this to flat roofs and cathedral ceilings without attic spaces.
What it covers
- 9.19.1.1. Required Venting
- 9.19.1.2. Vent Requirements
- 9.19.1.3. Clearances
- Objective
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