Roofs that have locations where roof meets wall surfaces are referred to as ‘complex roofs’. These intersections are locations where debris can accumulate, and also embers. The wall surfaces may not provide the same resistance to fire as the roof covering.

The shingle siding shown in this photograph is far more vulnerable than the Class A asphalt composition roof covering. Note debris accumulation on the roof in area adjacent to the shingle siding. If the debris is ignited by embers, the resulting fire will expose both roof and siding. This is another way that the fire protection provided by a Class A roof can be by-passed.

In this case, removal of debris on a regular basis is a critical component to maintaining a fire safe building.

This is an example of a complex vegetative (green) roof. The front of the dormer has a window in it. If the roof is ignited by embers, the fire won’t likely penetrate through soil layer, but it could spread laterally up the roof, potentially resulting in a flame impingement exposure on adjacent material. In this case, a flame impingement exposure on the window could result in glass breakage, and ignition of interior components.

Another example of a complex roof. In this if embers ignited the roof debris, flame would impinge on the siding, and flame and embers could enter the attic through the gable end vent. Again, removing debris from the roof should be a routine maintenance item.