Polyvinyl or vinyl siding on residential structures has been around for several decades, and there is a long and well-documented history of the effects of heat with this type of exterior wall covering.
According to the Vinyl Siding Institute, 78 percent of new homes constructed in the northeastern United States in 2008 and 32 percent nationwide are clad in vinyl siding. Vinyl siding is commonly found in one- and two-family wood frame dwellings, large apartment complexes, hotels and some commercial structures.
Most of us have seen melted or warped vinyl siding on structures that have been exposed to heat from a fire. A more immediate concern to firefighters is the rapid fire spread threat that vinyl siding poses with new home construction.
In 1997 Dan Madryzkowski conducted a study for the National Institute of Standards and Technology on the combustibility of several different types of siding materials. This NIST report describes the test results for vinyl siding: “Less than 90 seconds after ignition, the flames began to spread upward, and within another 50 seconds, the flames were in the attic space.”
This is a very significant finding for firefighters to consider when facing today’s engineered wood frame structure fire.
Nontraditional thinking
It is critical to identify any exterior fire spread involving vinyl siding or the potential for this threat during the 360-degree size-up. Once the vinyl siding ignites, rapid exterior fire spread can occur.
Traditional tactical thinking would have us by-pass this exterior fire and quickly move operations to the interior of the structure.
In 2010, a Fargo, N.D. apartment complex was destroyed after a fire rapidly extended up the vinyl siding from the ground level patio. It breached the vinyl soffit and spread fire into the open attic void, which resulted in a Mayday situation for two firefighters operating on the top floor.
However, a quick “hit it hard from the yard” tactical approach may be the only means by which you will have a chance to save the structure and buy time for occupant egress or rescue. Getting water on the fire fast minimizes all other problems.
Fire path
Vinyl siding produces a very high heat release rate and has been likened to “solid gasoline” when burning. As the burning vinyl is consumed, a fresh layer of pre-heated fuel from the synthetic underlayment and the wood wallboard is exposed and ready to burn.
This demands an attack with enough water to knock down the fire, and still penetrate the thermal column, which is blasting superheated gases and flames into the attic space. In addition, if this is a three- or four-story structure the added stream reach is necessary.
Now consider the wind-driven or the super-charging effect that can be created once the soffit melts and allows fire to rapidly spread via this natural flow path into the attic space. Winds as low as 10 mph can create wind-driven fire effects.
This scenario can become a monster fire very quickly and is capable of cutting off the escape routes of occupants, and trapping unsuspecting firefighters without warning, often with tragic results. A quick and aggressive hard hit is necessary before the fire takes complete control of the attic, which typically will doom the structure.
Proper tools
Several tools will give you better options for this type of fire attack. Use a 1 3/4-inch line with a 15/16-inch solid bore tip, capable of flowing approximately 180 gpm at 50 psi. This is the minimum recommended flow for a rapidly growing fire.
Another good tool of choice is either a 2 1/2-inch pre-connected blitz attack line or a large-flow pre-connected or pre-plumbed appliance that can be placed in service within a minute by one firefighter and is capable of 300- to more than 500-gpm flow.
Lastly, don’t forget about the exposures. Protect them early. Less water is needed to protect the exposure than is needed for extinguishment.
Vinyl siding is capable of melting several hundred feet away, and is notorious for quick fire spread to exposed structures. Closely spaced homes and apartment structures can quickly pose a major challenge early on at these fires.
