Building Codes and Roofs: Useful Guidelines

Roof Online Staff – Updated November 11, 2021

Also see Energy Codes.

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Building codes change, and this means design changes.
Code changes mean design changes.
Building codes have been around for a very long time (Code of Hammurabi, the earliest known building code).
Code of Hammurabi, the earliest known building code, among other things. (Images: Louvre, Paris; Public Domain)

Basics of “Roofing Codes”

Generally, there isn’t actually any such thing as a separate “roofing code”. There are, however, quite a few roofing sections of the building code.

Note: If you are trying to find sections of the code that cover specific roofing details, see our Roofing Guide to the International Building Code or our Roofing Guide to the International Residential Code.

Codes that Govern Roofing

There are two model building codes which form the basis of almost all of the building codes in the United States. The International Residential Code for One- and Two-Family Dwellings (IRC) covers one- and two-family home of three stories or less, and the International Building Code (IBC) covers all other buildings.

Other model codes which are referred to in the IBC and the IRC (and may be relevant to roofing) include the International Fire Code, the International Mechanical Code (covers HVAC systems), and the International Plumbing Code (covers roof drainage).

The International Energy Conservation Code (IECC) is of particular importance to low-slope roof design due to its R-value requirements, which affect the amount of insulation that has to be included in roof assemblies.

All of these codes are produced by the International Code Council (ICC).

The primary roofing chapter in the IBC is “Chapter 15 – Roof Assemblies and Rooftop Structures“. However, many other parts of the code deal with aspects of roofing; for help finding them see our Roofing Guide to the IBC.

The primary roofing chapter in the IRC is “Chapter 9 – Roof Assemblies“. For help finding other parts of the IRC which deal with roofs, see our Roofing Guide to the IRC.

Versions of the Building Code

Always check with your local building inspector’s office to be certain which version of the building code is in effect in your area.

New versions of the IBC and the IRC are produced every 3 years, but they are not adopted or put into effect by local authorities every 3 years. In fact, they are not adopted with any consistency from country to country, state to state, or even city to city.

You can usually find out which code is in force by going to the website of your local government, although some of these websites are so hard to navigate that it makes more sense to simply call and speak to someone in the building inspector’s office.

If you do call, in addition to asking which year’s code is in effect, be sure to ask about amendments to the code that might affect your project.

Amendments to the Building Code

An important thing to be aware of is the fact that the majority of the governing authorities which adopt the codes do so with amendments.

Local authorities can (and they do!) add things, remove things, change the language, and make exceptions to the model code, so it’s not enough to simply know which version of the model code has been adopted.

For instance, while the other US state codes that we’ve looked at use the exact same language of the model code regarding fastening asphalt shingles (four nails per shingle, except in designated high wind areas, where it’s six per shingle), the State of Rhode Island has amended the code so that the Rhode Island code requires something different.

From the actual Rhode Island version of the International Residential Code:

“R905.2.6 Delete R905.2.6 and substitute the following:

R905.2.6 Attachment.

Asphalt strip shingles shall have a minimum of six fasteners per shingle.”

So Rhode Island, by amending the model code, considers their entire state to be a high wind area where asphalt shingles are concerned.

Even governments at the municipal level in many states have further amended the version of the code adopted (and amended) at the state level, so you can see why it’s important to double-check and read the relevant sections of your actual local code.

Finding Your Local Building Code Online

You should be able to see the code that is in effect in your area on your municipal website, or there should be a link to a state website that has it. You should be able to find it in the “Building Inspection” or “Office of the Building Inspector” section of the website.

If not, the website UpCodes publishes full up-to-date versions of current state codes that include the local amendments.

UpCodes’ database isn’t complete, but they’re working on it, and they add codes for new jurisdictions frequently. You may or may not be able to search their site for free (that seems to change), but if you do a google search with “upcodes” as one of the terms, like “upcodes Texas asphalt shingles”, one of the first search results should take you right where you want to go.

1. General: For a terrific building code reference book, see Building Codes Illustrated: A Guide to Understanding the 2018 International Building Code by Francis D. K. Ching and Steven R. Winkel. Link goes to the book’s Amazon page.*

2. General: If you’re looking for code information about a specific type of roofing or roof component, see All Roofing Topics on our home page. Most of our topic pages provide links to the relevant code sections for the topic.

3. General: Our page, Roofing Guide to the International Building Code, helps you find every section in the IBC that has anything to do with roofing.

4. General: Our page, Roofing Guide to the International Residential Code, likewise helps you find every section in the IRC that has anything to do with roofing.

5. GeneralCodes And Standards Organizations Relevant To Roofing

6. General: Insulation R-Value: For code requirements, see Roof Online’s Energy Codes page.

7. General: A best practices “RICOWI Roof Guide” is available on the website of the Insurance Institute for Business & Home Safety. (“RICOWI” stands for the Roofing Industry Committee on Weather Issues). This is an excellent resource with particularly good explanations of building code requirements as they pertain to roofing.

8. General: Copyright law regarding building codes: This: Veeck v. Southern Bldg. Code Congress Int’l, Inc.yet also this: Federal Court Basically Says It’s Okay To Copyright Parts Of Our Laws. We don’t know what to make of it all. (And now this: Can the Law be Copyrighted?.)

9. GeneralThe Building Codes and Standards page at the website of the National Roofing Contractors Association is a good place for up-to-date information about building codes and how they affect roofing.

10. Building Codes: To view actual, current (including amendments) US state building codes, plumbing codes, fire codes, etc., see UpCodes (an excellent little start-up which we wish all the best).

Example: see here for a look at the roofing section of the 2018 International Building Code, without amendments as adopted by the State of Wyoming.

Example: See here for a look at the roofing section of the 2015 International Residential Code, with amendments as adopted by the State of Washington.

11. Building Codes2018 International Building CodeChapter 15 Roof Assemblies and Rooftop Structures. On the UpCodes website.

12. Building Codes2018 International Building Code: Also extremely relevant to roofs, with sections on rain loads, snow loads, and wind loads: Chapter 16 Structural Design. On the UpCodes website.

13. Building Codes2018 International Building CodeSnow Loads: As an example of what you can find in Chapter 16 of the 2018 IBC, see: Section 1608 Snow Loads. On the UpCodes website.

14. Building Codes2018 International Building CodeRoof Access: See Chapter 10 Means of Egress, particularly 1011.12 Stairway to roof1011.12.2 Roof Access, and 1011.16 Ladders.

15. Building Codes2018 International Residential CodeChapter 9 Roof Assemblies. On the UpCodes website.

16. Building Codes2018 International Residential CodeChapter 8 Roof-Ceiling Construction. Contains sections covering roof framing, roof sheathing, and roof ventilation. On the UpCodes website.

17. Building Codes2018 International Residential Code: Rafters: As an example of what you can find in Chapter 8 of the 2018 IRC, see: R802.4 Rafters. On the UpCodes website.