Roof Curb - 18 inch Tall

Roof Curb for Mounting Curb Mount Flange Vents and Fans
Roof Curb available with matching roof cap

AVP's Roof Curbs fit Roof Vents and Exhaust Fans with a Curb Mount Flange

A roof curb is a box that acts as an extension from the roof deck. This extension provides a base for a roof vent or exhaust fan. These roof curbs are intended for flat roofs only.

AVP’s Roof Curbs are made from aluminum and are offered in 3 height options. For climates with heavy snowfall, an 18 inch tall roof curb is ideal.

An important reason for the use of a curb is a roofing manufacturer's warranty. Many EPDM, PVC & TPO roofing manufacturers require roofing penetrations to be secured by a curb and a boot. Check with your roofing materials supplier to purchase a boot that slides over the aluminum curb.

The boot provides a factory-approved attachment to the roof deck’s membrane. The upper end of the boot folds into the curb. Then the curb mount flange goes over both the boot and curb. This will provide a perfect seal from the top.

Outer Width

Inside Opening

15"13"18"For a 12" Diameter Vent or FanRC-12-H18
17"15"18"For a 14" Diameter Vent or FanRC-14-H18
19"17"18"For a 16" Diameter Vent or FanRC-16-H18
21"19"18"For a 18" Diameter Vent or FanRC-18-H18
23"21"18"For a 20" Diameter Vent or FanRC-20-H18
27"25"18"For a 24" Diameter Vent or FanRC-24-H18
33"31"18"For a 30" Diameter Vent or FanRC-30-H18
39"37"18"For a 36" Diameter Vent or FanRC-36-H18
45"43"18"For a 42" Diameter Vent or FanRC-42-H18
51"49"18"For a 48" Diameter Vent or FanRC-48-H18


An additional benefit to using an 18 inch tall roof curb is it can act as a hatch or access entry port. The roof vent or exhaust fan can be easily removed. As a result, allowing for quick access to ductwork, electrical lines, or maintenance in the attic below.

Traditionally, roofers build wooden boxes on the roof at the time of the membrane installation. Using prefabricated aluminum curbs reduces the time and need to build wooden boxes. This will also lower the risk of injury during installation by lowing the time spent on the roof. In addition, any chances to damage the roof in the building process are also lower.

Another safety feature is that aluminum curbs are not flammable. The majority of curbs vent out heat from range hoods or HVAC units. This can cause wooden curbs to burn. However, aluminum will not burn, rust, or corrode. Aluminum curbs are safer and easy to clean.

For any questions, please email us at [email protected] or call at 845-565-7770

Shop roof curbs on AVP’s website:

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