Building Codes and Roofing: Facts, Tips & Guidelines

Introduction

First of all, I’d like to point out that a roof covering (roof system) is not considered a structural building component, so you tend to have more leeway and less code detail when it comes to roofs than with most other parts of a building. The roofing sections of the building code will even occasionally just instruct you to simply follow the manufacturer’s installation instructions. The non-structural aspect of a roof is one reason that roofers don’t always need a professional license to ply their trade.

The roof deck and supporting (load-bearing) structures like rafters and trusses are structural, though, and of course you can’t just disregard the parts of the building code that do very specifically regulate roofing. The codes can get very specific when it comes to fire resistance, wind uplift, and storm drainage, among other things.

Roofs are an essential component of any building, providing protection from the elements and helping to preserve a building’s structural integrity. While the primary function of a roof is to act as a barrier against water intrusion, it also plays a role in fire mitigation, thermal insulation and energy efficiency, and ventilation. 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: Overview

Building codes ensure that buildings are safe for use and meet certain standards developed to protect public health and safety and are enforced by government agencies and building inspectors. If they follow the building codes, roofing contractors and building owners can generally assume that their work and their properties are safe and meet the requirements of the law.

The National Institute of Standards and Technology describes building codes 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 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 inspection departments and actual building inspectors in the field. In the U.S., roofing codes are primarily governed by the International Residential Code (IRC) and International Building Code (IBC), developed by the International Code Council (ICC).

Building inspectors are responsible for verifying that construction projects follow all codes and relevant regulations in effect in their jurisdiction. They usually 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. The model codes produced by the ICC contains language pertaining to this discretion. Some jurisdictions may have stricter enforcement policies.

Model building codes are developed by private organizations (this pretty much just means the International Code Council these days) and serve as the basis for all local building codes. Model codes are designed to be used as templates for the actual codes adopted by state and municipal 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. Developments in roofing materials, energy saving priorities (increasing R-value requirements), and wind resistance standards have led to roofing updates in recent code editions.

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 because of Florida’s efforts to address the performance of roofs under high wind conditions (in hurricane-prone regions). Following Hurricane Andrew in 1992, Florida implemented significant improvements in its roofing codes, including stricter fastening requirements for shingles and enhanced uplift resistance criteria for roof assemblies.

Building codes are an essential part of the construction process, and the roofing sections of the code are an essential part of roof construction.

“Roofing Codes”

So there isn’t actually any such thing as a separate “roofing code” even though that’s a common search term on Google. But there are 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’re trying to find the particular sections of the code that cover specific aspects of a roof installation, see my Roofing Guide to the International Building Code or its counterpart, 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. They cover the 2018 codes (which are still in effect in many places); your local code may be more recent (or possibly older) and be slightly different, but they will point you in the right direction.

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. Many major roofing material manufacturers work closely with and advise the building code organizations on code updates pertaining to roofing. Reputable manufacturers keep up-to-date on code developments and update their roofing products and their installation guidelines as needed. (But read about code amendments below).

One example of this is the way asphalt shingle manufacturers update their specified nailing patterns and fastening requirements so that their installation recommendations and instructions align with both the IBC and high-wind zone amendments in Florida and other hurricane-prone regions.

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 have sections that pertain to roofing) include the International Fire Code, the International Mechanical Code (which addresses ventilation and exhaust systems, including roof penetrations for HVAC equipment), and the International Plumbing Code (which governs roof drainage, including scupper and gutter requirements).

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. This isn’t much of a concern for most residential roof installations where the insulation is in the attic and isn’t a part of the roof system.

The International Energy Conservation Code is technically a separate code, but state codes often simply incorporate it into the state building code. In addition to insulation, the IECC also mandates air barrier performance, cool roofing standards in some climates, and solar reflectance requirements for commercial buildings to improve energy efficiency.

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. Remember that these codes are just templates, and state and local jurisdictions frequently amend them to address regional climate concerns, such as increased wind resistance in hurricane-prone areas or enhanced snow load requirements in colder regions.

The big roofing chapter in the IBC is “Chapter 15 – Roof Assemblies and Rooftop Structures,” which covers roofing materials, installation methods, wind resistance, and much more. Be aware that many other chapters of the code also deal with aspects of roofing.

The main roofing chapter in the IRC is “Chapter 9 – Roof Assemblies,” which provides standards for residential roofing materials such as asphalt shingles, metal roofing, clay and concrete tile, and wood shakes, along with requirements for underlayment, flashing, and a lot more. It also has a section on reroofing (roof replacement or recover); Appendix J of the IRC also addresses the retrofitting of existing structures, which can be important for reroofing projects.

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. Local adoption timelines can vary significantly, and some areas may still be using versions that are several cycles behind the latest model codes.

New versions of the model IBC and the model IRC are produced every three years, but they are not adopted or put into effect by local authorities on that same schedule. In fact, they are not adopted with any consistency from state to state, county to county, or even city to city. Some jurisdictions may skip multiple code cycles before updating their building codes, often due to cost concerns, the imprudence of always changing things every three years, or the need for review to tailor requirements to local conditions.

You can usually find out which code is in force by going to the website of your local government, although some of these websites either don’t have the information or are so hard to navigate that it makes more sense to simply call and speak to someone in the local building inspector’s office. Some states do provide online resources where you can check the current building codes for multiple municipalities within the state.

If you do call your local building department, 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 that adopt the codes do so with amendments. These amendments may be implemented at the state, county, or municipal level, meaning that even within the same state, different cities may enforce different rules for roofing projects.

Some amendments may be minor, such as clarifications of definitions, but others can turn out to be big changes to roofing requirements, possibly forbidding certain materials, changing acceptable fastening methods, or enacting strict energy efficiency mandates.

Model vs. Actual 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. This is particularly true for roofing-related provisions, as areas prone to hurricanes, earthquakes, wildfires, or extreme snowfall often modify the code to address those specific local issues. California severely regulates the use of wood shingles due to wildfire concerns, for example.

Historic preservation concerns may also affect what you’re allowed to do. For historic buildings, additional roofing regulations may apply beyond what is stated in the code. In historic preservation zones, materials, colors, and even installation methods may be restricted to maintain the character of the building or neighborhood, meaning that the full range of modern roofing options might not be permitted without special approval.

Example of a Local Jurisdiction Amendment

Here’s a case that concerns asphalt shingles: while many US state codes 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 installing asphalt shingles.

From the actual Rhode Island amended 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. Similarly, states such as Florida and Texas also have strict wind uplift resistance requirements, while colder areas may enforce additional underlayment and ice dam protection rules.

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. Some states maintain a central database listing which versions of the codes have been adopted in each jurisdiction, so checking the state’s building department website is also a good idea.

You should be able to find current code information in the “Building Inspection” or “Office of the Building Inspector” section of the website. In some cases, it may be under “Permitting” or “Code Enforcement.” If you’re having a hard time finding it, try using the website’s search function with terms like “building code adoption” or “roofing requirements.”

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. If amendments are not posted online, contacting the local building department is the best way to make sure you have the most up-to-date information.

Another Good Resource

If not, the UpCodes website has full up-to-date versions of current state codes that include the state-level amendments, and even the municipal-level amendments for some cities. They also highlight differences between versions, which can be useful if a jurisdiction has recently updated its code or is using an older version.

UpCodes’ database isn’t complete, but they’re working on it, and they add codes for new jurisdictions frequently. They also integrate code references with easy-to-use navigation, making it simpler to find specific roofing requirements. UpCodes is a third-party source, though; you should always verify information with official government websites or local authorities.

You may or may not be able to search their site for free (that seems to change), but if you do a web 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.

If you don’t find what you need there, another useful site for checking building codes is the International Code Council (ICC) website, which offers free online viewing of model codes, although they do not have amended versions and some sections may require a paid subscription.

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. Their role is primarily to ensure compliance rather than to interpret or modify the code based on personal judgment.

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. This discretion is typically exercised when the code language is ambiguous, when alternative methods provide equivalent safety and performance, or when strict compliance is impractical due to site conditions.

The purpose of the building code, according to Chapter 1 of the building code itself (R101.3 Purpose), is:

“The purpose of this code is to establish minimum requirements to provide a reasonable level of safety, health and general welfare through affordability, structural strength, means of egress, stability, sanitation, light and ventilation, energy conservation and safety to life and property from fire and other hazards and to provide a reasonable level of safety to firefighters and emergency responders during emergency operations.”

Chapter 1 further goes on to say (Section R104.2.3 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, provided the building official shall first find that one or more special individual reasons make the strict letter of this code impractical, and the modification is in compliance with the intent and purpose of this code and that such modification does not lessen health, life and fire safety or structural requirements. The details of the written request for and action granting modifications shall be recorded and entered in the files of the department of building safety.”

So modifications can be granted for practical reasons, as long as they don’t interfere with safety or the structural components of a building. These modifications must be documented, and many jurisdictions require formal approval through a variance process or an alternative means-and-methods request.

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 I know this from personal experience) financial considerations. I want to point out that financial hardship alone is generally not an accepted reason for code modifications unless combined with other practical difficulties.

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. That said, modifications related to roofing must still comply with energy efficiency, drainage, wind, and fire resistance requirements, etc.

A Real Life Case of a Code Modification

I’ll tell you about a time I 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 if there are two existing roofs in place, “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 without oversight from one of their representatives.

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 who owned the building for a budget estimate (before we really got involved or even looked at the building), I 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, as it turned out.

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

The decking 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. This would of course expose and damage their roof deck, which meant they would have to be involved because of their patent and a lack of any official tests or standards regarding their system. 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 technically 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 since the cost would prevent the roof replacement from happening at all. It was an unnecessary obstacle to the roofing project. 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.

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.