Traveling on my way to work, I drove past a garage that was being “renovated,” so to speak. What really caught my interest was the method of transformation this building experienced. Many times buildings are renovated and rarely have any problems with the end result. However, comparing Photo 3 (the finished result) and Photo 4 (during construction) suggests that many surprises lay in wait within this garage. The smart Incident Commander (IC) who familiarizes oneself with construction in the surrounding area can feel confident with the tactics deployed at an emergency. This one suggests a defensive posture early upon arrival.
Our crew was sent out to perform a Smoke Detector Compliance Test at a residence that was being sold in our community. While we were there, the owner asked us to assist in changing the battery within the attic detector. Entering into the attic was not through a scuttle hatch; it was through a full-size door. Apparently, the owner “renovated” this space to allow for additional storage within the attic. His plan included sawing out multiple web posts and the king post within a series of trusses in the attic space over the garage (Photo 5). Moreover, the bottom chord of this peak roof truss is now in compression, instead of tension, because of the weight of the stored materials transferred to the floor. This area can collapse even without being ravaged by flames, but most responders wouldn’t know it by looking from the exterior.
We responded to a partial collapse of a carport after a delivery truck hit the underside of the roof assembly. Upon arrival, the carport overhang was obviously displaced on the columns supporting it, but did not seem to be significant in nature. Further investigation was needed to check the interior and underside of the roof assembly, exposing a lightweight metal truss assembly within the carport (Photo 6). Responding to this facility on routine alarms usually places one apparatus within the underside of this carport; since the discovery, the staging area for apparatus has now been changed.
Stopping by a construction site for a new retail store, I was curious about a truss assembly that had been placed off to the side of the site. These trusses were doubled up, constructed of wood and metal, and had engineered wood thrust blocks within the webs of the assemblies (Photo 7). I took the pictures to one of the engineers on our USAR (urban search and rescue) team, and he explained to me that these are Wood Chord, Metal Web Truss Assemblies (WCMW Truss). The WCMW truss is used in the roof assembly where there exists a significant concentrated load, perhaps an HVAC unit, ventilation system assemblies, and the like. Assembling these units includes a ¾” pin through both the chord and the web ends, connecting the metal webs to the chords. The insertion of this pin leaves a little more than ½” of material above and below the pins, making for a significant weak point in the assembly.
Repairs to structures are not usually exposed for all to see; in Photo 8, repairs were made to a five-story heavy timber structure in a neighboring community. While spreader plates are common within Type III and IV construction, symmetrical placement of these plates suggests that the building was designed to use these plates and tension rod assemblies. The beams in place in this application are serving as a “tie-back” for this wall. This is a red flag, for any response. This area must be avoided at all costs.
Looking at Photo 9, the obvious renovations are what draw your attention. Further looking at the area in question, there are multiple types of construction/loading within this wall, along with multiple layers of outside covering and siding. These clues suggest this building has been experiencing numerous problems throughout its lifespan. Additionally, changes to the loading of exterior walls can have a serious impact on how the rest of the structure is supported.
Chief Brannigan was a proponent of pre-planning buildings within the firefighter’s response area, as this arms the IC with as much knowledge about how the building was constructed prior to the fire. I continue to seek out hazards within our response area, and share this knowledge with as many people as I can. I challenge you to do the same; take your crew out for a “field trip” and look to see what is going around in front of you. I will bet that you will be surprised by what you will find, especially when you go out looking for it.
Until next time, stay focused and stay safe!