Talking in Code: Roof replacement requirements
Want to know more about roof truss failures? Have a question about fire-rated assemblies? Confused about safety glazing on windows and door? In our monthly column — Talking in Code — International Code Council code experts will address some of the typical questions asked of our technical services team regarding current code issues. This feature is not an ICC code opinion, nor is it a committee interpretation, but it is intended to provide clarification of code text for adopting jurisdictions, design professionals and members of the construction industry.
International Code: 2018 International Energy Conservation Code
Sections: C503.1 and C503.3.1
Question: What is the requirement for a roof replacement when the roof is part of the building thermal envelope and the existing roof has no insulation?
Answer: There are two conditions that have different answers. First, if the existing roof cavity is not exposed, there is no requirement per Exception 4 of Section C503.1. Second, if the existing roof cavity is exposed, insulation is required to the extent to which the cavity can be filled per Exception 3 of Section C503.1.
In the first condition, where the roof cavity is not exposed, Exception 4 of Section C503.1 exempts the roof replacement from the insulation requirements regardless of whether or not there is insulation at the roof. For instance, if the existing asphalt shingles are being replaced and there is no additional work being done at the roof sheathing, the code would not require the addition of insulation on the roof.
In the second condition, where the roof cavity is exposed, Exception 4 of Section C503.1 is not applicable. Exception 3 of Section C503.1 would be applicable. In such a case, the code would only require the cavity to be filled. The intent of the code is that the insulation be provided to improve the energy efficiency of the building to the extent possible without requiring the alteration of the structural elements at the roof to allow for more insulation. For instance, if the existing asphalt shingles are being replaced and a portion of the roof sheathing is removed, the code would require as much insulation as the existing cavity would accommodate. If the code requires R-38 insulation in an attic for new construction but the existing cavity is only deep enough to allow for R-19 insulation, then R-19 would be the requirement.
It should be noted that Section C503.3.1 does not apply to a roof with no insulation because it only applies to roof replacements where the insulation is entirely above the roof deck. In such a case, where the insulation is entirely above the roof deck, the code would require the roof to comply with the provisions of the code for new construction because the work would not typically necessitate alterations to the structural portions of the building to meet the requirement.
As always, code opinions issued by International Code Council staff are based on published Code Council codes and do not include local, state or federal codes; policies; or amendments. This opinion does not imply approval of an equivalency, specific product, specific design or specific installation and cannot be published in any form implying such approval by the International Code Council. As this opinion is only advisory, the final decision is the responsibility of the designated authority charged with the administration and enforcement of this code. All code citations reference the 2015 and 2018 International Codes unless otherwise specified.