Exterior Wall Fire Demonstration

Steve Quarles, PhD (UC Cooperative Extension Advisor Emeritus) is an expert on how building materials perform and how different building designs fare in wildfires. He conducted an exterior wall fire demonstration to compare fiber-cement siding vs cedar shingle siding.

Here are the details of the setup:
Left Hand Side assembly: fiber-cement siding, redwood deck (with door mat, broom and B brand on top), metal gutter, two flame and ember resistant vents in wall under the deck (two different types / brands), asphalt comp shingle roof covering

Right Hand Side assembly: cedar shingle siding, redwood deck (with same stuff on top as left hand assembly), vinyl gutter with foam insert intended to minimize accumulation of debris in the gutter, one flame and ember resistant vent and one vent with 1/4-inch mesh screening in wall in under-deck area, asphalt comp shingle roof covering

Summary:
Combustible deck and items on top of the deck ignited. Combustible siding allowed fire to spread to the under-eave area and into what would be the attic. Vertical flame spread did not occur on the assembly with the fiber-cement siding.