Roofing Codes • Building Code Facts & Guidelines for Roofs

By Jack Gray, Roof Online Editor Last updated August 27, 2023

Also see our Energy Codes article.

Building codes change, and this means design changes.
Changes to the building code might mean that you have to change your plans.

Table of Contents

Building codes have been around for a very long time (Code of Hammurabi, the earliest known building code).
The code of hammurabi, the earliest known building code, among other things. (images: louvre, paris; public domain)


Roofs are an essential component of any building, providing protection from the elements and helping to preserve a building’s structural integrity. To ensure that roofs (among other things) meet desired standards for safety and functionality, building codes have been developed and enforced across the world.

Building codes ensure that buildings are safe for use and meet certain standards. These standards are designed to protect public health, safety, and welfare and are enforced by government agencies and building inspectors. By adhering to building codes, roofing contractors and building owners can ensure that their properties are safe and meet the requirements of the law.

Building codes regulate the materials, design, and construction techniques used for virtually all buildings, The codes have the force of law and are enforced by state and local building inspector’s departments and actual building inspectors in the field.

The National Institute of Standards and Technology puts it this way: “Building codes are laws that set minimum requirements for how structural systems, plumbing, heating, ventilation and air conditioning (HVAC), natural gas systems and other aspects of residential and commercial buildings should be designed and constructed.”

Building inspectors are responsible for ensuring that building codes are adhered to during construction and renovation projects. They have some discretion in enforcing the code and may allow changes or modifications as long as the building meets safety standards and meets the intent or spirit of the code.

Model building codes are developed by private organizations such as the International Code Council and serve as the basis for all local building codes. They are designed to be used as a template for the actual codes adopted by state and local authorities.

State legislatures or city councils enact and authorize the codes in order to promote public safety, health, and welfare, and they are updated periodically to reflect changes in building technology and best practices.

Amendments to the building code are often made by local jurisdictions to address specific concerns or local issues. For example, after a hurricane or other natural disaster, local building codes may be updated to improve building performance in the future. The Florida building code is somewhat famous for its efforts to address the performance of roofs under high wind conditions (in hurricane prone regions).

Finding your local building code online has become easier in recent years, with many state or even local governments making these codes available through their websites. These online resources often include information on the specific requirements for roofing in your area, as well as the permits and inspections required.

The building code is an essential part of the construction process, and the roofing sections of the code are an essential part of roof construction.

Basics of “Roofing Codes”

So there isn’t actually any such thing as a separate “roofing code” even though we called this article “Roofing Codes…”. (We’re trying to help people find the information they’re looking for, and everyone seems to be searching for “roofing codes”.)

There are, however, quite a few sections in the various actual building codes that deal with roof coverings, roof systems, roofing materials, roof flashing, roof decking, roof slope, thermal insulation, and so on.

If you are trying to find the 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. Those articles list just about all of the applicable provisions from every part of every chapter of the codes that mention roofs.

One reasonably good way to ensure that your roof covering is applied in accordance with the codes is to read and follow the manufacturer’s installation instructions. Reputable manufacturers keep up-to-date on this and update their roofing guidelines as needed. (But read about code amendments below).

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 homes of three stories or fewer, and the International Building Code (IBC) covers all other buildings.

Other model codes which are referred to in the IBC and the IRC (and which 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 thermal insulation R-value requirements, which affect the amount and type of insulation that has to be included in roof assemblies. The International Energy Conservation Code is technically a separate code, but state codes often simply incorporate it into the state building code.

All of these model building codes are produced by the International Code Council (ICC), and you can view them for free on the International Code Council website.

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 inspection department to be certain which version of the building code is in effect in your area.

New versions of the model IBC and the model 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 them if there are any local 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.

Model Building Codes

The codes produced by the International Code Council are model codes, which means that they are simply standardized templates that the authorities in actual jurisdictions can use as a foundation for their building codes. Some places will adopt the codes as they are, without amendments, but this is not very common.

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.

Example of a Local Jurisdiction Amendment

Here’s an example that concerns asphalt shingles: 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 state building code requires something different when you’re applying shingles.

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 the Rhode Island state government, by amending the model code, effectively considers their entire state to be a high wind area as far as asphalt shingles are concerned. If you just looked at the model code, you might think that four nails per asphalt shingle would be enough, but in Rhode Island, you’d be wrong.

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 which version of the building code is in effect in your area on your local municipal website (the official website of your town or city), or the local website should at least have a link to the appropriate page on your state website.

You should be able to find it in the “Building Inspection” or “Office of the Building Inspector” section of the website.

In addition to telling you which version of the code is in effect, the building inspection section of the state or local website will typically make the full text of any code amendments available, even if the entire building code is not reprinted on the site.

Another Good Resource

If not, the website UpCodes publishes full up-to-date versions of current state codes that include the local state amendments, and even the municipal-level amendments for some cities.

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” (without the quotation marks), one of the first search results should take you right where you want to go.

Discretion of the Building Inspector

Building inspectors are not generally allowed to use their own discretion when enforcing building codes. They are expected to follow the specific requirements set forth in the building codes that have been adopted in their jurisdictions as well as any other applicable regulations.

However, building inspectors do have some degree of flexibility in how they enforce these requirements. They may accommodate reasonable deviations from the code in certain situations and they are permitted to make judgment calls, especially on minor issues that do not pose a significant safety risk.

Purpose of the Building Code

The purpose of the building code, according to Chapter 1 of the building code itself, is

“to establish the minimum requirements to provide a reasonable level of safety, public health and general welfare through structural strength, means of egress facilities, stability, sanitation, adequate light and ventilation, energy conservation, and safety to life and property from fire, explosion and other hazards, and to provide a reasonable level of safety to fire fighters and emergency responders during emergency operations.”

Chapter 1 further goes on to say (Section 104.10 Modifications) that

“Where there are practical difficulties involved in carrying out the provisions of this code, the building official shall have the authority to grant modifications for individual cases, upon application of the owner or the owner’s authorized agent, provided that the building official shall first find that special individual reason makes the strict letter of this code impractical, the modification is in compliance with the intent and purpose of this code and that such modification does not lessen health, accessibility, life and fire safety or structural requirements.”

So modifications can be granted for practical reasons, as long as they don’t interfere with safety or the structural components of a building.

Practical reasons can include the builder’s desire to use a product or material that the building code has not yet acknowledged, the need to accommodate physical restrictions caused by the configuration of a particular site or existing building, or even (and we know this from personal experience) financial considerations.

Low-slope roofing is one area where it’s relatively easy (relatively!) to get a building inspector to grant a code modification. This is because the roof is neither a structural component of the building, nor does it normally have much of an effect on safety.

A Real Life Case of a Code Modification

I’ll tell you about a time we got a very important code modification approved during a re-roofing project that saved our client around $200,000.

We were hired to handle a roof replacement project on a commercial flat roof on one of the buildings in a shopping center. While we were doing the field investigation of the existing roof (prior to writing the specifications for the new roof) we discovered that there were two existing roofs in place on the building.

Now, Section 1511.3 of the IBC (Roof Replacement) states that “roof replacement shall include the removal of all existing layers of roof coverings down to the roof deck.”

And furthermore that “a roof recover shall not be permitted where any of the following conditions occur…(w)here the existing roof has two or more applications of any type of roof covering.”

In other words, there were two roofs already in place, and we were going to have to have the contractor remove all of the existing roofing as part of the job.

So that’s fine, we do that all the time. But there was a hitch. A big problem. A serious issue.

The roof decking in place on the building was a type of patented, composite decking made out of light-gauge, ribbed sheet metal overlaid with a proprietary gypsum board.

(All the roof consultants and roofing contractors I know hate to find this deck on a building. I’m not going to name the manufacturer, but they know who they are and so does everyone else in the roofing industry.)

The issue was that in order to proceed with the project according to code, we would have to tear the roof off down to a patented and proprietary deck that the manufacturer claimed would lose structural integrity if the old roof was pulled off of it.

We would have to pay for that manufacturer to send an inspector to inspect the decking for integrity issues during the entire job. And then we would have to buy their proprietary gypsum board to make repairs as they directed.

And we would have to buy their proprietary insulation system to install over the entire deck in our new roof system. Their proprietary insulation simply being normal polyiso board that had their brand name stamped on it or some such nonsense.

When we were first contacted by the client (before we got involved or looked at the building) for a budget estimate, we told them the project would likely cost around $300,000. (Which did end up being perfectly in line with the final cost of the job.)

Paying for the inspection and design services and buying the proprietary roofing materials from this deck manufacturer would have added $200,000 to the total cost.

The deck manufacturer counted on this. They knew that they had the code on their side. In fact, after I got in touch with them and expressed shock at the fact that they were charging 3 times as much as any other manufacturer for basically the same products, they sent me an email which fully quoted the building code section about completely removing the roofing down to the deck. They knew what they were doing.

It was actually the second email from the manufacturer’s representative/salesman quoting that building code section about removing all existing roofing materials that gave me the idea of asking for a code modification. I had been trying to figure out how to proceed. $500,000 was way beyond the client’s budget, and simply outrageous in general.

What if we just removed the top layer of roofing instead of all the roofing? What if we just took off the second existing roof?

If we did that, we would never touch or even see this proprietary roof deck, and after we installed the new roof, there would still only be two layers of roofing on the building, which is permitted by code!

I sent the local building inspector a fairly long email introducing myself as a roof consultant and the owner’s representative, and thoroughly explaining the issue, including the financial aspect of it, and then detailing the solution I had come up with.

The building inspector agreed that the extra cost that we were currently looking at was indeed a practical reason to ask for a modification, and an unnecessary obstacle to the roofing project. And after all, the building was in serious need of a new roof.

He told me that my solution would satisfy the spirit of the building code, and officially gave his approval.

He asked for regular reports with pictures to prove that we weren’t pulling off the bottom layer of roofing (and thus interfering with the roof deck), and that was the end of it. The project was back on track, and the bids from the roofing contractors all came in near our initial estimate.

Leaving the bottom roof in place during a roof replacement to satisfy the building inspector
Look, we left the bottom roof in place!

Ultimately, the goal of the building official is to ensure that buildings are safe and meet the minimum standards set by the building codes. If you can demonstrate that you will meet that goal, you may get a code modification if you need one.

About the Author

Jack Gray is a principal roof consultant and vice president at the Moriarty Corporation, an award-winning building enclosure consultant firm founded in 1967. He is also the editor of the Roof Online website.

Mr. Gray has worked in the roofing industry for over 25 years, with training and practical experience in roof installation, roof inspection, roof safety, roof condition assessment, construction estimating, roof design & specification, quality assurance, roof maintenance & repair, and roof asset management.

He was awarded the Registered Roof Observer (RRO) professional credential in 2009.

He also served as an infantry paratrooper in the 82nd Airborne Division and has a B.A. from Cornell University. Read full bio.

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. General: The 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 2021 International Residential Code, without amendments as adopted by the State of Colorado.

11. Building Codes: 2018 International Building Code: Chapter 15 Roof Assemblies and Rooftop Structures. On the UpCodes website.

12. Building Codes: 2018 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 Codes: 2018 International Building Code: Snow 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 Codes: 2018 International Building Code: Roof Access: See Chapter 10 Means of Egress, particularly 1011.12 Stairway to roof1011.12.2 Roof Access, and 1011.16 Ladders.

15. Building Codes: 2018 International Residential Code: Chapter 9 Roof Assemblies. On the UpCodes website.

16. Building Codes: 2018 International Residential Code: Chapter 8 Roof-Ceiling Construction. Contains sections covering roof framing, roof sheathing, and roof ventilation. On the UpCodes website.

17. Building Codes: 2018 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.