I am sure if you talk to most fire service professionals about an area of basic knowledge that is lacking in today’s fire service it won’t take long to hear the topic of building construction surface. Knowledge of building construction and how a fire reacts in that building is an area that is extremely under taught and misunderstood by today’s fire service. It amazes me that we teach safety officers to spot a gloveless hand at 100 yards but we spend very little time talking about the hazards of balloon frame buildings, knee walls, fire spread issues, ordinary construction, etc. With the changes in building construction nowadays and more and more emphasis of our training time on everything not fire related (ie. EMS, underwater HAZMAT, etc.) we need to teach building construction even more today than we ever have had to in previous years.
A cornice in architectural terms that describes a horizontal decorative molding that usually is found at the tops of doorways or building, for the purposes of the article we are going to look at them on the tops of flat roof buildings.
In the 19th and early 20th century, cornices were a very common place and most buildings were not complete without decorative cornice work adorning the top of the structure. The functionality of the cornice was simple, to deflect and cause rain water to run off of the building and keep the water from running down the side of the brick work. The intent was to save the brick work from the wear and tear of mother nature, essentially these decorative moldings were flat roofed buildings example of gutters or eves troughs.
Cornices came to favor in the 19th and 20th century but are in fact much older that that and have there roots all the way back to Roman times. Cornices as we know them in North America come in many different styles but the two most common types are wood and brick. It is important to note the building construction material used in these cornices before it is too late; brick cornices will hold up much better than there wood counterparts to weather and fire deterioration. Wood cornices are the more dangerous of the two types of cornices and for the purpose of this article we will talk about the hazards associated with only wood cornices. Wooden cornices are generally not attached very well to the buildings facade, typically they have been nailed in when the building was first built and very little maintenance or thought goes into them until there is a problem. Wooden cornices have been known to fall off buildings under snow loads and because of natural breakdown and deterioration of the wood and nails holding the cornice to the building. When cornices start to become problematic for firefighters is during roof operations and if fire showing from windows starts to involve the cornices.
When engaged in flat roof operations at one of these older style taxpayers or any other type of older building with a flat roof it is imperative that you take a quick second see if wooden cornices are present. The reason for this is that in some cases the cornices are not on a parapet and are in fact flush with the roof. In many they cases are completely tarred over, this will prevent you from knowing whether you are standing on a solid roof or only standing on the cornice. If you are accessing the roof via aerial ladder, it is vital that if you have to step off the aerial onto the cornice to aggressively sound the cornice area with a roof or rubbish hook before stepping on it. Several firefighters have been injured and killed by cornices failing without ever being subjected to fire… they simply gave way under the load of the firefighter operating on them.
Fire Impingement onto Cornices
In building fires where the fire has vented out windows and the fire has started to impinge on the cornice an early and catastrophic collapse of sections of the cornice should be expected. Also the wooden construction of the cornice can cause the fire to extend along the face of the building. When dealing with a fire involving sections of cornices a collapse zone should be set up and respected. During over haul the stability of the cornice should be checked, roof firefighters could attempt to remove it through traditional overhaul means or a from a tower ladder. Also a stream from smoothbore nozzle could be used to attempt to knock the loose section of cornice off. You want to try to control when the cornice will fail and not have it happen unexpectedly.
This is just one small building construction feature that firefighters often overlook the hazards of. Francis L. Brannigan’s famous saying “know your enemy, the building is your enemy” holds even more true today, be sure to practice, train, study, (and most importantly) get out in your area and study building construction features common in the buildings in your district.
Cornice Collapse Video – Fast forward to the 6:25 min mark.