An exhaust hood roof curb may appear to be to be nothing more than a metal box that surrounds your rooftop exhaust sits on top of, however, it is important to point out that they serve a specific function for your upblast exhaust fan. Without a roof curb, there wouldn’t be a secure way to mount the fan to the rooftop. The rooftop fan would also be exposed to weather threats, including the internals of the fan.

If you have a commercial kitchen and are planning on installing an upblast exhaust fan then you will definitely need a roof curb. In cases where a wall mounted exhaust fan is used, you can get away with using a mounting bracket as opposed to the roof curb. In the case that you have a wall mounted exhaust fan but would still like a curb there are options available for that as well.

There are two types of curbs - pitched roof and flat. In most cases, you will use a flat curb, however in the case that you have a slanted roof above your restaurant a pitched curb can be used to match the slope. Standard height of the curbs is approx 20”, however, it is necessary to measure the height of the upblast exhaust fan just to be sure the overall height to the top of the fan from the roofline is 40” .it’s properly covered by the 20” height. You will also need to measure the base of your fan in order to get the proper size curb - generally, you want to size the roof curb to be around 1.5” to 1.75” smaller than the base of your fan to ensure a proper fit and to allow the use of a hinge kit.

The curb does not enclose the fan. The fan sits on top of the curb. The distance from the roofline to the top of the fan mounted on the curb must be 40” per code.

When installing a roof curb first be sure that you are adhering to all state and local guides to ensure you’re meeting their requirements. Ductwork must be located at a minimum of 18” from any roof surface per NFPA 96 7.8.2.1, and the discharge from the upblast fan must be a minimum of 40” from any roof surface. The installation requires the curb to be securely fastened to the vertical portion of the fan base assembly, and it is recommended to use a minimum of at least 8 anchor bolts or other fasteners.

HoodMart.com is your one-stop hood exhaust hood shop for high-quality commercial and restaurant kitchen exhaust, grease, odor and fume ventilation equipment. Every commercial kitchen exhaust hood & ventilation system is available with pre-piped fire suppression If you have any questions relating to roof curbs, installation, or any other exhaust hood questions you can contact a HoodMart professional at any time using our chat portal or by calling 1.800.715.1014.