FHB Logo Facebook LinkedIn Email Pinterest Twitter Instagram Plus Icon Close Icon Navigation Search Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Subscribe
Log In
  • How-To
  • Design
  • Tools & Materials
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
Log In

Fine Homebuilding Project Guides

Roofing

Guide Home
  • Tools and Materials
  • Roof Replacement and Reroofing
  • Roof Ventilation
  • Waterproofing
  • Installing Asphalt Shingles
  • Installing Other Types of Roofs
  • Roof Maintenance and Repair
Job Site Diaries

Ice-Dam Protection: How Far Up the Roof Slope?

Here's why 3 feet probably isn't high enough to meet code.

By Mike Guertin

Most roofers install one 3-ft.-wide roll of self-adhering ice barrier membrane along the eave edge to prevent leaks due to ice dams. On most roofs this isn’t far enough to comply with the International Residential Code. Section R905.1.2 Ice Barriers in the 2018 IRC says the ice barrier “… shall … extend from the lowest edges of all roof surfaces to a point not less than 24 inches inside the exterior wall line of the building.”

The 24 in. is measured horizontally, so when you figure in a typical eave overhang and the wall thickness and then calculate how far up the roof slope the membrane has to reach, it exceeds the typical 36-in. sheet width.

A couple of examples of how far up the slope of the roof the ice barrier membrane must be installed:

6 pitch roof with a 12 in. overhang and a 2×6 exterior wall: 47 inches up the roof slope from the drip edge

8 pitch roof with a 12 in. overhang and a 2×6 exterior wall: 50-1/2 inches up the roof slope from the drip edge

12 pitch roof with a 12 in. overhang and a 2×6 exterior wall: 59-3/8 inches up the roof slope from the drip edge

So what’s the harm if the ice barrier isn’t applied far enough up the roof slope?

During winters when there is a lot of snow and ice dams form higher up the roof slope, water can pond up behind the dams and reach higher than 36 in.  The winter of 2014-2015 in my southern New England area reinforced the need for ice barriers to be installed according to the code.  Heavy snowfalls coupled with melting and refreezing temperatures resulted in larger ice dams than usual.  Homes that had never experienced roof leaks were damaged by ice-dammed water flooding inside ceilings and walls.  In the cases I examined, had the ice barrier been installed according to the code, there likely would not have been leaks.  By installing the ice barrier up to the prescribed point, there is less of a chance of leaks occurring.

Check out the other parts of this series on ice barriers:

  • Ice Barriers Explained: Do You Need It or Not?
  • Ice Barriers Explained: What Materials Can You Use?

These articles and podcast episodes shed more light on the topic:

  • Ice-Dam Protection: How Far Up the Roof?
  • Ice Dams
  • Podcast Episode 37
  • Podcast Episode 50

www.mikeguertin.com |  @mike_guertin

Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters
Previous: Ice Barriers Explained: What Materials Can You Use? Next: Ice-Dam Protection: Over or Under Eave Drip Edge?

Guide

Roofing

Chapter

Waterproofing

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Roofing

Roofing

A complete resource that includes the best materials and the right techniques to build a sturdy, leak-free, attractive roof on any house

View Project Guide

View All Project Guides »

Become a member and get unlimited site access, including the Roofing Project Guide.

Start Free Trial

Tools and Materials
  • Roof Coverings
  • Roofing Materials
  • Power Tools
  • Handy Helpers
  • Staging and Ladders
  • Safety Equipment
Roof Replacement and Reroofing
  • Preparing the Old Roof
  • Sheathing
  • Installing the New Roof
Roof Ventilation
  • Venting Basics
  • Installation
Waterproofing
  • Underlayment
  • Drip Edge
  • Flashing Adjoining Walls
  • Dormer and Skylight Flashing
  • Chimney Flashing
  • Vent Flashing
  • Gutters
Installing Asphalt Shingles
  • Calculating Shingles
  • Layout
  • Installation
  • Valleys
Installing Other Types of Roofs
  • Cedar Shingles
  • Metal
  • Low-Slope Roofs
  • Slate and Tile
Roof Maintenance and Repair
  • Assessing the Problem
  • Repairing Asphalt-Shingle Roofs
  • Other Roofing Repairs

Fine Homebuilding

Follow

  • twitter
  • facebook
  • instagram
  • pinterest

Newsletter

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Privacy Preferences

Taunton Network

  • Green Building Advisor
  • Fine Woodworking
  • Fine Gardening
  • Threads
  • About
  • Contact
  • Advertise
  • Careers
  • Copyright
  • Terms of Use
  • Site Map
  • Do not sell or share my information
  • Privacy Policy
  • Accessibility
  • California Privacy Rights

© 2023 The Taunton Press, Inc. All rights reserved.

X
X
This is a dialog window which overlays the main content of the page. The modal window is a 'site map' of the most critical areas of the site. Pressing the Escape (ESC) button will close the modal and bring you back to where you were on the page.

Main Menu

  • How-To
  • Design
  • Tools & Materials
  • Video
  • Blogs
  • Forum
  • Reader Projects
  • Magazine
  • Members
  • FHB House

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Popular Topics

  • Kitchens
  • Business
  • Bedrooms
  • Roofs
  • Architecture and Design
  • Green Building
  • Decks
  • Framing
  • Safety
  • Remodeling
  • Bathrooms
  • Windows
  • Tilework
  • Ceilings
  • HVAC

Magazine

  • Current Issue
  • Past Issues
  • Magazine Index
  • Subscribe
  • Online Archive
  • Author Guidelines

All Access

  • Member Home
  • Start Free Trial
  • Gift Membership

Shop the Store

  • Books
  • DVDs
  • Taunton Workshops

More

  • FHB Ambassadors
  • Reader Projects
  • Podcast
  • FHB House
  • Customer Support

Account

  • Log In
  • Join

Newsletter

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Follow

  • twitter
  • facebook
  • instagram
  • pinterest

Join All Access

Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

Start Your Free Trial

Subscribe

FHB Magazine

Start your subscription today and save up to 70%

Subscribe

We hope you’ve enjoyed your free articles. To keep reading, become a member today.

Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

Start your FREE trial

Already a member? Log in