What types of materials are prohibited in the construction of exterior walls for one- and two-family dwellings?

The prohibition of non-fire-resistant materials in the construction of exterior walls for one- and two-family dwellings is grounded in safety regulations designed to protect structures and occupants from fire hazards. The International Residential Code (IRC) specifies that exterior walls must be constructed from materials that have adequate fire resistance to minimize the risk of fire spread and protect the integrity of the dwelling.

Non-fire-resistant materials can behave unpredictably in the event of a fire, potentially allowing flames to penetrate walls more easily, which can lead to rapid fire spread and increased risk to life and property. By requiring fire-resistant materials, the code aims to provide a critical barrier that can delay the spread of fire, thereby offering occupants more time to evacuate and firefighters more time to control the situation.

This focus on fire safety is why the use of non-fire-resistant materials is explicitly prohibited in these types of constructions. In contrast, while wood and plastic materials may have specific applications within certain code guidelines, they can be used in ways that comply with fire resistance requirements when properly treated or in conjunction with protective systems. Insulated panels can also be utilized so long as they meet the fire safety standards outlined in the IRC.