
Example of how to calculate net free area:
1200 square foot attic divided by 150 square feet = 8 square feet (1200 / 150 = 8)
8 square feet times 144 square inches = 1152 square inches (8 x 144 = 1152)
1152 square inches divided by 2 = 576 square inches at soffit and at exhaust (1152 / 2 = 576)
The information below was originally compiled by www.hvac-buzz.com. I have since researched www.up.codes and discovered information that could be slightly different or information that pinpoints specific pipe venting termination lengths. Please do your own research on the building code relevant to each roof project before installing any products.
Building Code Requirements for Minimum Plumbing Vent Height Requirements Above Roof
There are 41 States (see below) that have a minimum plumbing vent height above the roof requirement of less than 9 inches (Roofing contractors are recommended to use Bullet Boots when installing roofs in these States.)
There are 7 states with 12 inch minimum height requirements for plumbing vents: Connecticut, Delaware, Indiana, Minnesota, Montana, Ohio, and Rhode Island (It's recommended for these States to use the Bullet California Boot because of its taller design meeting the 12 inch minimum. If the pipe is higher than 12 inches above the roof, the pipe may be reduced in length to stay within the minimum code requirements while allowing the Bullet California Boot to fit within the manufacturer specifications and installation instructions).
New Hampshire has a minimum requirement of 18 inches.
Vermont has a 6 inch minimum to a maximum of 12 inches for pipes plumbing vents to extend above the roof.
The details for each State is below in alphabetical order:
Alabama
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1 Residential Code 2015 of Alabama
Alaska
6” above roof OR 6” above firewall OR 7’ above roof (roof used as assembly or parking area)
Section 906.1 Section 906.3 Uniform Plumbing Code 2018 of Alaska
Arizona
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 Residential Code for One- and Two-family Dwellings as amended by the city of Phoenix
Arkansas
6” above roof OR 7’ above roof (roof used as assembly or parking area)
Section 903.1 2018 Arkansas Plumbing Code
California
6” above rood OR 6” above firewall OR 7’ above roof (roof used as assembly or parking area)
Section 906.1 Section 906.3 California Plumbing Code 2019
Colorado
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 Residential Code 2021 of Colorado
Connecticut
12” above roof OR 7’ above roof (roof used as living space)
Section P3103.1 2015 IRC portion of 2018 CT State Building Code
Delaware
12” above roof OR 7’ above roof (roof used as living space)
Section 903.1 2018 State of Delaware Plumbing Code
Florida
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 2020 FBC – Residential 7th edition
Georgia
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 Georgia State Minimum Standard One and Two Family Dwelling Code
Hawaii
6” above roof OR 6” above firewall OR 7’ above roof (roof used as assembly or parking area)
Section 906.1 Section 906.3 Uniform Plumbing Code 2018 of Hawaii
Idaho
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 International Residential Code 2021
Illinois
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 Residential Code 2018 of South Holland
Indiana
12” above roof OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 2020 Indiana Residential Code
Iowa
6” above roof OR 6” above firewall OR 7’ above roof (roof used as assembly or parking area)
Section 906.1 Section 906.3 Uniform Plumbing Code 2021 of Iowa
Kansas
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 Residential Code 2018 of Kansas
Kentucky
6 inches above roof OR 7' above roof (roof used as living space)
Section 903.1 Plumbing Code 2018 of Kentucky
Louisiana
6 inches above roof OR 6 inches above projected snow line OR 7' above roof (roof used as living space)
Section P3103.1 Residential Code 2015 of Louisiana
Maine
2 inches above roof OR 2 inches above firewall OR 7' above roof (roof used as living space) [it appears this statement might conflict with the interpretation of the following details: 906.0 Vent Termination 906.1 Roof Termination Each vent pipe or stack shall extend through its flashing and shall terminate vertically not less than two (2) feet (610 mm) above the roof nor less than one (1) foot (305 mm) from any vertical surface. ]
Section 906.1 Section 906.3 Uniform Plumbing Code 2021 of Maine
Maryland
6 inches above roof OR 7 inches above roof (roof used as living space)
Section 903.1 Plumbing Code 2018 of Maryland
Massachusetts
6 inches above roof OR 6 inches above projected snow line OR 7' above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 International Residential Code 2021
Michigan
1 inches above roof OR 7' above roof (roof used as living space)
Section P3103.1 2015 Michigan Residential Code
Minnesota
12” above roof OR 7’ above roof (roof used as anything but weather protection)
Section 906.1 Section 906.3 2020 Minnesota Plumbing Code
Mississippi
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 Residential Code 2018 of Mississippi
Missouri
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1 Residential Code 2015 of Missouri
Montana
12” above roof OR 12” above firewall
Section 906.1 Section 906.3 Uniform Plumbing Code 2021 of Montana
Nebraska
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 Residential Code of 2018 of Nebraska
Nevada
6” above roof OR 6” projected snow line OR 7’ above roof (roof used as living area)
Section P3103.1.1 Section P3103.1.2 Residential Code 2018 of Nevada
New Hampshire
18” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 Residential Code for One- and Two-Family Dwellings of the State of New Hampshire
New Jersey
6” above roof OR 7’ above roof (roof used for anything but weather protection or maintaining equipment)
Section 12.4.1 New Jersey Plumbing Code 2018
New Mexico
6” above roof OR 6” above firewall OR 7’ above roof (roof used as assembly or parking area)
Section 906.1 Section 906.3 2021 New Mexico Plumbing Code
New York
6” above roof OR 6” above projected snow line OR 7′ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 2020 Residential Code of New York State
North Carolina
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1 2018 North Carolina Residential Code
North Dakota
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 Residential Code 2018 of North Dakota
Ohio
12” above roof OR 7’ above roof (roof used as living space)
Section 903.1 Ohio Plumbing Code 2017
Oklahoma
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 Residential Code 2018 of Oklahoma
Oregon
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 2021 Oregon Residential Specialty Code
Pennsylvania
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 Residential Code 2018 of Pennsylvania
Rhode Island
6” above roof OR 12” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 2021 Rhode Island State One and Two Family Dwellings
South Carolina
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 South Carolina Residential Code 2021
South Dakota
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 International Residential Code 2021
Tennessee
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living area)
Section P3103.1.1 Section P3103.1.2 Residential Code 2018 of Tennessee
Texas
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living area)
Section P3103.1 Residential Code for one- and two-family dwellings of the Texas Industrialized Housing and Building Program
Utah
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1 Residential Code 2015 of Utah
Vermont
6” to a maximum of 12” above roof
Section 903.1 Plumbing Code 2018 of Vermont
Virginia
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 2018 Virginia Residential Code
Washington
6” above roof OR 6” above firewall OR 7’ above roof (roof used as assembly or parking area)
Section 906.1 Section 906.3 2018 Washington State Plumbing Code
West Virginia
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 Residential Code 2018 of West Virginia
Wisconsin
8” above roof OR 7’ above roof (roof used as living area)
Pg. 44 Vent Terminals Wisconsin Drain and Vent System Design by the Wisconsin Department of Commerce
Wyoming
6” above roof OR 6” above projected snow line OR 7’ above roof (roof used as living space)
Section P3103.1.1 Section P3103.1.2 International Residential Code 2021
Roof flashing refers to any roof component overlapping another component and protecting the roof area by allowing water to continue the path down the sloped roof; so as to as to shed or guide the water to the eaves.