Ontario Building Code Practice Exam 2026 - Free Building Code Practice Questions and Study Guide

The minimum height required for a guardrail on a balcony in a commercial building is 1100 mm. This ensures the safety of individuals using the balcony as it is high enough to prevent falls. The other options are incorrect because 900 mm is too short and may not adequately protect against falls, while 1200 mm is unnecessarily high and can add unnecessary costs during construction. Similarly, 1000 mm is not the minimum height required and does not meet the safety standards for a guardrail in a commercial building. Therefore, the best answer is 1100 mm.