When is a curb required for a roof jack or ventilator?

A curb is required for a roof jack or ventilator when it is taller than 10 inches to ensure proper installation and functionality. The height of the curb is critical because it provides a solid support base that raises the jack or ventilator above the roof surface. This elevation helps prevent water from pooling around the base of the jack or ventilator, which can lead to leaks or water damage. Additionally, having the unit elevated allows for better ventilation and helps mitigate the impact of snow and ice build-up on the roof.

Installing a curb also aids in aligning the ventilator or roof jack with the existing roofing materials and ensures that the flashing can be properly fitted to create a watertight seal. Thus, adherence to this specification reflects best practices in HVAC sheet metal work and roofing standards.