Although roof curbs are a basic metal box, their function is vital to your commercial fan system. Without a roof curb, it would be impossible to attach your fan securely to the roof. A mechanical roof curb also serves the primary purpose of protecting your exhaust system's interior from the elements.

Do I really need a roof curb or a roof rail?

A roof curb is required if you plan to install an exhaust fan onto your rooftop commercial kitchen. Mounting an exhaust fan on the wall is possible with a bracket. Roof curbs are manufactured and are constructed of high-quality, heavy-duty aluminized steel.

Curbs less than 36 inches in length or width are made of 20 gauge steel, while curbs larger than 36 inches in length or width are made of 18 gauge steel. You can purchase prefabricated mechanical roof curb via for your commercial building. 

Roof curbs are air-tight, watertight, and feature continuous flashing of 3''. Pitch roof curbs can be customized to fit the slope of a roof if needed. Ventilated roof curbs are required by some cities and states. These can also be ordered in special cases. If you are unsure, check with your local authorities before placing an order.

How big a roof curb should I use?

Companies offer these roof curbs in seven sizes, from 17.5" square to 42.5" square. Roof curbs can be installed up to 20 inches high. To find the size of the roof curb you need, simply measure your exhaust fan. Your roof curb should be 1.5'' to 1.75'' smaller in size than the base of your fan.