Wildfires are no longer limited to remote forests. They're hitting closer to home and causing more damage than ever before. Fires that used to be seen as a seasonal concern have become a year-round threat, especially in areas that weren't considered high risk in the past.
In just the first five months of 2025, more than 25,000 wildfires have burned across North America. They've destroyed over a million acres and thousands of homes, businesses, and buildings along the way.
That kind of devastation is forcing a shift in how we think about fire safety. More builders, architects, and code officials are turning to WUI-specific building regulations. These codes are built for areas where wildland meets development and where older standards just don’t cut it.
In this post, we’ll break down why WUI compliance matters and how it can help reduce the risk in the places that need it most.
Key Takeaway
- WUI codes are gaining traction as wildfire risks spread into formerly low-risk zones.
- The 2023 Lahaina Fire underscored the need for updated codes like the IWUIC, which set new standards for ignition-resistant construction.
- Compliance begins with materials that meet benchmarks like SFM 12-7A-1 and UL 263 or ASTM E119 fire-resistance ratings.
- MAXTERRA® magnesium oxide non-combustible structural wall sheathing is WUI compliant and enables one-hour fire-rated assemblies with standard fiberglass insulation and nearly any cladding.
Lessons from Lahaina: Maui Wildfires and the Need for Updated Fire Codes
The 2023 Lahaina Fire was a turning point. In just a matter of hours, the blaze tore through the town of Lahaina on Maui, destroying more than 2,000 structures and taking 102 lives. It was one of the deadliest fires in Hawaii’s history and one of the worst urban fire disasters the US has seen in decades.
In the aftermath, the state commissioned a forward-looking report to understand what went wrong and how to prevent it from happening again. UL’s Fire Safety Research Institute led the investigation. Their top recommendation? Begin adopting the International Wildland-Urban Interface Code (IWUIC).
The IWUIC outlines practical steps to reduce wildfire risk before disaster strikes. It addresses everything from land use planning to the materials used in construction, especially in areas where homes and businesses are built close to wildland vegetation.
The message was clear: stronger codes save lives, and support quickly followed from major organizations like the International Code Council (ICC) and the National Fire Protection Association (NFPA).
The Lahaina Fire was a loud call to action for communities across North America. The time to upgrade fire safety isn’t someday. It’s now. And the IWUIC is the first step toward building a safer future.
What Is the WUI Code? Understanding the Wildland Urban Interface
The Wildland-Urban Interface (WUI) is where homes, businesses, and other buildings exist in close proximity to natural vegetation. As cities grow, development often pushes into forests, grasslands, and other spaces with wildland fuels. That creates buffer zones between developed areas and wildlands, placing structures in these regions at higher risk.
As of 2022, the WUI includes more than 46 million homes across over 70,000 communities in the US alone. That means more than 100 million Americans live in areas with a significantly higher risk of wildfire damage.
Because of this, WUI regions need their own building codes that reflect the risks of the surrounding landscape. These WUI codes reduce that risk by setting standards for land use, defensible space, and ignition-resistant construction. They can be used alone or alongside local fire and building codes to prevent structure fires triggered by nearby vegetation.
The International Wildland-Urban Interface Code is the most widely adopted of these guidelines. It sets minimum requirements for safeguarding life and property in wildfire-prone areas, and the 2021 version expanded those protections further to include all structures that could contribute to wildfire spread, not just those directly in high-risk zones.
Why the Wildland Urban Interface Code Is Shaping Fire-Resilient Construction?
The WUI Code was designed to protect communities in wildfire-prone areas. It has already gained traction in states like California, Colorado, and Hawaii. But with climate change driving more intense fire seasons, regions that haven’t historically dealt with wildfires are beginning to take a closer look at these standards.
Some core codes include guidelines for building defensible spaces between buildings, using ignition-resistant roofing, siding, and wall systems, and avoiding combustible materials in construction. While not every part of the IWUIC may fit a dense urban environment, many of its core principles can still make a difference, and adopting even a few of these elements can help reduce the risk of wildfire damage.
What Makes a Building Material WUI Code Compliant?
WUI compliance starts with your building materials. To meet the standard, they need to undergo extensive fire testing to prove they can hold up when it counts. Inspectors are looking at how easily something ignites, how fast flames can spread across it, how well exterior wall systems stay intact, and whether the roof meets the right fire rating.
On top of that, they’re checking for certifications like:
- SFM 12-7A-1 from the California State Fire Marshal
- UL 263 or ASTM E119 fire-resistance listings
- Non-combustible materials in accordance with ASTM E136
- WUI Product Index ratings depending on the region
The reality is that many common construction materials just don’t cut it, especially when it comes to siding, decking, or insulation. That’s why more builders and code officials are switching to magnesium oxide (MgO) products that meet IWUIC standards. They’re tough, fire-resistant, and meet the benchmarks without forcing you to sacrifice design or performance.
MAXTERRA® MgO Non-Combustible Structural Wall Sheathing allows you to use standard fiberglass insulation and virtually any exterior cladding in ignition-exposed zones while still achieving a one-hour fire rating. In contrast, many common fire-resistant sheathing materials require the use of mineral wool insulation or limit cladding options to brick or stucco in order to meet the same standard. MAXTERRA® provides performance without compromise.
Building Safer Communities with WUI-Ready Materials
WUI isn’t just a code. It’s a smarter way to think about fire safety. As wildfire risks grow, more jurisdictions are adopting the International Wildland-Urban Interface Code. Nearly 200 are already on board across 24 states.
This shift toward fire-adapted construction takes coordination across the board. And while the full code won’t apply everywhere, its core principles can improve safety in almost any setting.
WUI-compliant materials play a big role in that. When you start with the right products, it’s easier to meet code, reduce long-term risk, and build confidence in wildfire-prone areas.
Whether it’s new construction or an update to what’s already there, it’s worth thinking about fire-ready design now to save yourself from disaster in the future.
Questions from the Field
1. How does MAXTERRA® support WUI compliance?
MAXTERRA® MgO Non-Combustible Structural Wall Sheathing is tested to meet important fire safety standards like ASTM E119 for one-hour fire resistance and ASTM E136 for non-combustibility. Structural panels are rated as fully non-combustible in accordance with the criteria for ASTM E136-22 (as referenced by the 2024 IBC and 2024 IRC). These certifications meet the requirements under the International Wildland-Urban Interface Code (IWUIC), making MAXTERRA® a smart option for areas that face wildfire risk.
2. What makes MAXTERRA® different from other fire-rated sheathing boards?
Many fire-rated panels limit what you can use for insulation or exterior finishes. MAXTERRA® lets you stick with standard fiberglass insulation and still meet a one-hour fire rating. You also have more freedom when it comes to cladding, which means more flexibility, fewer compromises, and less hassle on site. Check out the fire resistance overview for more details on how it performs in rated assemblies.
3. Can MAXTERRA® help speed up construction?
Absolutely. Since MAXTERRA® delivers both structural support and fire resistance in one panel, you don’t need to add extra fireproofing layers. This can help speed up overall build times while allowing you to cut material costs. In the end, MAXTERRA® MgO panels will help keep you on schedule and on budget, all while keeping you code compliant.
4. What certifications does MAXTERRA® have?
MAXTERRA® has been tested on ASTM E119, ASTM E136, and ASTM E84. It holds a Flame Spread Index of 0. These tests show how the product performs under serious fire exposure, which gives you and your inspectors more peace of mind when building in higher-risk areas. You can learn more about MAXTERRA® certifications on our product pages.
5. Where can I see how MAXTERRA® MgO Non-Combustible Structural Wall Sheathing performs in a fire-rated wall assembly?
You can watch our Leveraging Innovation to Maximize WUI Code Benefits video. In this demo, we showcase how a wall assembly built with MAXTERRA® MgO Non-Combustible Structural Wall Sheathing measures up to a WUI-compliant generic wood assembly.