Building Construction for Firefighters

Five Critical Building Construction Factors for Structure Fire Size-Up When sizing up a structure fire, consider these five essential building factors to evaluate how the structure will withstand fire, how it might spread, and what will be required for extinguishment: A. Type of Construction Knowing the type of construction allows firefighting crews to assess potential fire spread routes and estimate how quickly the fire will extend through the structure. This information is vital for positioning fire attack teams ahead of the fire, identifying weak points that might fail under fire exposure, and establishing collapse zones. Stronger areas of the building can also be used as defensive positions to protect uninvolved sections. Evaluate building materials... B. Size of the Building The size of the building helps determine the extent of fire involvement and provides an approximation of potential fuel and occupant loads. This, in turn, guides the allocation of firefighting resources needed to control and extinguish the fire. Additionally, understanding the building’s physical dimensions and the fire’s location allows incoming crews to estimate the required hose line lengths to effectively reach and combat the fire. More info on building size... C. Age of Construction The age of the building can reveal whether it was constructed with conventional or lightweight materials, which directly impacts how long it will withstand fire conditions. Conventional construction generally allows for longer operational periods, whereas lightweight construction fails more quickly under fire stress. Identifying the building’s age can also reveal specific structural characteristics, such as pre-1933 masonry in California, which poses more of a hazard due to outdated building codes. Over time, structures may suffer from mortar erosion, metal corrosion, or wood rot and insect infestation, all of which degrade structural integrity. To estimate the age of a building, start by observing its overall appearance. What kind of siding does it have?  Due to the cost of construction, labor intensive sidings like board and batten, and wooden clapboard are not generally built, so the presence of these types of siding would suggest an older structure.  Due to the cost of maintenance, wood siding is used less frequently today. Vinyl sidings are becoming more prevalent in new construction.  Vinyl siding is also used in remodeling buildings, so its presence may be deceptive.  No one (1) indicator should be relied on solely when estimating the age of a building.  Look at the rafter tails, if visible, two-by-four (2 x 4) rafter tails indicate either a very old building, or lightweight construction.  Look at the condition of the roof.  Older structures may have a noticeable sag to the roof due to the age, the added weight of several layers of roofing and the fact that codes were less stringent regarding size and spacing of roof rafters.  How many layers of roofing are present?  Older structures may have several layers of different roofing materials.  Most roof systems were expected to last fifteen (15) to twenty (20) years, so a building with three distinct roof layers is probably at least thirty (30) years old, depending on how old the top layer of roofing is.  These are just some examples of ways of visually estimating the age of a building. D. Renovations Renovations can significantly alter a building’s structural integrity. When a building is renovated, structural elements might be removed or modified, weakening the structure even if it continues to bear the same or greater loads as before. This reduction in the building’s original safety factor can increase the risk of collapse during a fire. Renovations also complicate the assessment of the building’s age and type of construction, requiring firefighters to be even more diligent during inspections to accurately evaluate the structure. More on building renovations and fire safety... E. Type of Occupancy The building's occupancy type informs the approach to firefighting and resource allocation. For example, at 3:00 PM, occupants of a residential complex are likely awake and can self-evacuate. However, at 3:00 AM, most occupants are asleep and unaware of the developing fire, necessitating a different strategy and potentially more resources. Understanding the type of occupancy also helps anticipate the potential risks and challenges firefighters might face during rescue and suppression operations. More on occupancy and fire attack strategy...