By John W. Mittendorf
To date, this series has examined construction (lightweight vs conventional), roofs, and the styles of buildings. This installment continues with the methods of construction, focusing on metal, concrete, frame wood, frame stucco, fascias, masonry, and curtain.
Metal
These buildings fall into two basic categories: all-metal construction, and a metal frame structure with a decorative exterior. The all-metal buildings can use corrugated steel, corrugated aluminum, and corrugated fiberglass (which is not a metal, but looks like metal from the street). All three of these materials look identical from a distance but will act differently in a fire. Corrugated steel will last longer than aluminum or fiberglass. Aluminum and fiberglass will quickly fail when exposed to fire. Be familiar with the differences of these materials. Metal frame buildings will commonly use a metal frame structure, and then finish the exterior with glass, marble, decorative aluminum panels, brick veneer, or other similar items. A common example is a modern three-story office building that appears to be of brick construction. It would be easy for an unsuspecting firefighter to assume that the building offers:
- strength (brick veneer attached to an erector set does not equal strength); and
- a lack of vertical extension in the exterior walls (again, brick veneer attached to metal supports which are in turn attached to the metal frame structure leave plenty of room for vertical extension).
The metal frame type buildings are currently popular as the exterior can be quickly completed which provides protection for construction crews that are completing the interior of the building. A significant number of the metal frame buildings also employ “curtain construction” which will be examined in a later portion of this size-up series.
It is common knowledge that metal begins to fail at between 800 and 1,000 degrees. So, if the major component is metal and is exposed to fire, need we say more?
Concrete
Age and Construction
Concrete buildings are built like the proverbial brick outhouse, right? Yes and no. First, let’s define concrete building. For this discussion, let’s consider a concrete building as a building with solid concrete exterior walls. Now, when you hear the term building, what goes through your mind? Do you consider what you can see (the exterior walls), or the exterior walls, roof, and interior of the building? When we say concrete building, let’s assume that means exterior walls, roof, and interior construction. With this definition, we can place concrete buildings into two categories: older concrete buildings, and newer concrete tilt-up buildings. Expect older concrete buildings to employ conventional construction, and in some cases, the older style of timber construction. You can expect to find this conventional style of construction in the roof and interior construction (floor joists, ceiling joists, etc). Although the age of some of these buildings might have resulted in remodels that can detract from the strength of the original construction, these buildings can offer significant fireground time (as compared to modern buildings) and early collapse in a fire is not the norm. Conversely, newer concrete buildings (i.e., concrete tilt-up’s) have solid concrete exterior walls, but normally feature lightweight construction in the roof, and interior construction. Although the exterior walls seldom collapse, expect early collapse of the roof and portions of interior construction when exposed to fire.
Mezzanines
Remember that concrete tilt-up type buildings often have mezzanines that were likely constructed over the office area, may be of substandard construction, can support significant weight, and are located over the office area (also the main entrance point into the building).
John W. Mittendorf joined the Los Angeles City (CA) Fire Department (LAFD) in 1963, rising to the rank of captain II, task force commander. In 1981, he was promoted to battalion chief and in the year following became the commander of the In-Service Training Section. In 1993, he retired from LAFD after 30 years of service. Mittendorf has been a member of the National Fire Protection Research Foundation on Engineered Lightweight Construction Technical Advisory Committee. He has provided training programs for the National Fire Academy in Emmitsburg, Maryland; the University of California at Los Angeles; and the British Fire Academy at Morton-in-Marsh, England. He is a member of the editorial advisory board of Fire Engineering and author of the books Truck Company Operations (Fire Engineering, 1998) and Facing the Promotional Interview (Fire Engineering, 2003).
