WUI and Fire-Resistant Construction
If you haven't heard the acronym "WUI," let me introduce you. WUI stands for Wildland- Urban Interface, and although it has been around as a designation for many years, it has recently received more attention and implementation as a regional designation. In short, WUI designation indicates "the zone where human housing and development meet or mix with undeveloped wildland vegetation and open space." (FEMA Geospatial Resource Center). Although that definition gives a rather general description, WUI has been the source of many recent fire code developments, especially in forested areas with dry climates. Basically, WUI codes are an effort to answer the question "how do humans responsibly exercise dominion over nature?"
In Colorado, WUI fire codes were updated and accepted in 2025. They were implemented beginning in July 2026, so that all new exteriors must be WUI compliant. Here in Mesa County and Western Colorado, that means that when we build decks, we have to meet fire codes as well as building codes. When it comes to deck cladding materials, fire code specifies that
404.5 Decking. Unenclosed decks shall have the deck walking surface constructed of one of the following:
Approved noncombustible materials
Class A rated material
Exception: Composite decking material with a minimum of Class B rating
Fire-retardant-treated wood identified for exterior use and meeting the requirements of Section 2303.2 of the 2024 International Building Code
Ignition-resistant building materials in accordance with Section 402.4.
When it comes to designing outdoor spaces, we want to provide you with selections and techiniques that conform to WUI and local building department codes. Anyone considering building a deck will benefit from getting informed as to what materials are available, how they classify, and how we can build with them.
Some resources for your perusal:
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