Overhead: Dead Loads

Article and photos by Gregory Havel

Since we participated in our Basic Firefighter or Firefighter I class, we have been told repeatedly that at an incident, we must be aware of and avoid overhead hazards. The most commonly used example is overhead wires: electric, telephone, cable TV, and other wires as well as the overhead service drops from these lines to buildings. In addition to obstructing ladder, aerial ladder, and hoseline evolutions, these also present the potential for electric shock or electrocution of firefighters.

These overhead wires can be considered a part of the dead load supported by the line of poles to which they are permanently attached. The service drops from a pole to a building are also part of the dead load supported by the building.

There are other dead loads (supported by and permanently attached to the structure) that each firefighter needs to note during size-up and to work around during performance of their assigned tasks.

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Photo 1 shows an overhead dead load that is common on older multistory buildings: a fire escape. This is an eccentric load, since it is fastened to the face of the wall rather than being supported on top of it. It may also be a load that was not part of the original building design and that was added to meet fire or life-safety code requirements. Failure of connections because of age, deterioration, or overloading with potted plants or people can drop a fire escape to the sidewalk, seriously injuring anyone who is on it or under it. The counterbalanced stairway can also be an obstacle to raising ground ladders.

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Photo 2 shows a decorative wood cornice and an awning attached by brackets to the brick wall on the front of a building. These are also eccentric loads and probably were not part of the original building design.

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Photo 3 shows a 100-year-old building with its original decorative terra-cotta cornice supported by brick corbels and by the parapet wall behind it. It is an eccentric load on the wall and its connections can fail from age, from lack of maintenance, or from fire inside the wall supporting it. This building also has other dead loads that can be hazardous to firefighters:

The wood-framed canopy or mansard shading the display windows. This is a recent addition built of combustible materials. It may be poorly connected to the wall, and the concealed (void) space inside may be interconnected with the concealed space between the first floor ceiling and the second floor. (The potted plants hanging from the canopy are considered live loads—more about these in the next Construction Concerns column.)
The air conditioners in the boarded-up second-floor windows over the alley. If the window frames to which they are attached are rotten or burning, the air conditioners can drop into the alley and onto anyone walking below.
The chimney near the B-C corner of the roof appears to be of deteriorated masonry. It is likely to be unstable, and could collapse during a fire either into the alley or through the roof into the building.
Overhead wires are visible at the A-D and B-C corners of the building.

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We are all familiar with the hazards of air conditioners, exhaust ventilators, and refrigeration machinery concealed by lightweight wood-truss mansards on fast-food restaurants and similar occupancies. Photo 4 shows two large air conditioning units set on the roof of a 100-year-old wood-frame college dining hall with a timber truss roof system. It is obvious from the sagging roof supporting each unit that these are undesigned loads. Their presence is not so obvious on arrival at this building, since they are visible only from the B-C and C-D corners, and invisible from the A side.

Other common overhead dead loads on and inside buildings include:

Signboards that have been fastened to the wall
Large chandeliers, light fixtures, and ceiling fans
Rooftop antennas for radio, television, and satellite
Roof slates and tiles, especially when they are used on a roof structure that was not designed to support them. The weight per square foot (square meter) of slate or tile roof covering can be three to four times the weight of common asphalt shingles or wood shakes.

When responding to fire incidents, our personnel and company-officer size-up must go far beyond a check for overhead wires and power lines. We must note and be continually aware of all of the dead loads supported by the structure, especially if they were added to the structure (undesigned loads); if they are eccentric loads; and if the masonry or wood framing supporting them is seriously deteriorated. These can be important notes to add to our preincident plans for a building or occupancy.

Gregory Havel is a member of the Burlington (WI) Fire Department; a retired deputy chief and training officer; and a 30-year veteran of the fire service. He is a Wisconsin-certified fire instructor II and fire officer II, an adjunct instructor in fire service programs at Gateway Technical College, and safety director for Scherrer Construction Co., Inc. Havel has a bachelor’s degree from St. Norbert College; has more than 30 years of experience in facilities management and building construction; and has presented classes at FDIC.

Subjects: Building construction for firefighters

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