Ontario Building Code Practice Exam

The minimum slope required for a flat roof in a commercial building is 1/4 inch per foot. This is because a flat roof still needs some slope for proper drainage and to prevent water from pooling and causing damage. A slope of 1/4 inch per foot is the industry standard for flat roofs and provides enough slope to ensure proper water flow without making the roof too steep. The other options are incorrect because they either provide too little slope (A and C) or too much slope (D), which can result in drainage issues and potential damage to the roof. Therefore, option B is the most appropriate and accurate answer for the minimum slope required for a flat roof in a commercial building.