Mass Over Math

(Photos by author.)

It should be of no surprise to anyone involved in the fire service that the modern built environment is continuing to trend at a rapid rate toward incorporating lighter and dimensionally reduced building materials. Today, it is virtually impossible to find a newly constructed building that does not contain at least some type of engineered component or assembly hiding behind the walls.

I realize that this is a topic that consistently provokes strong debates. Before anyone starts to become defensive, pro or con, regarding a department’s current operating procedures relating to lightweight engineered construction, I want to make it perfectly clear that this article is not meant to criticize these operations.

I’ve always been very vocal regarding my personal belief that, with a thorough knowledge of building construction, a strong understanding of fire behavior, and an accurate size-up of both the extent and location of the fire, we can safely operate on and within lightweight constructed buildings. My thoughts on this subject were cultivated from the large portion of my life that was spent swinging a hammer, the education and technical training I received throughout my apprenticeship to become a journeyman carpenter, and my experience working for an urban fire department.

Regardless of the varying opinions relating to lightweight construction, I sincerely hope that we can all agree that the structures we are fighting fires in are constantly changing, and this requires continual education on and familiarization with both the strengths and weaknesses of existing and emerging engineered materials.

“New” Lightweight Engineered Construction

Lightweight engineered construction is not a new subject; structural components such as lightweight trusses, wood I-joists, and engineered lumber have been around and incorporated into our built environment for decades. I often find myself frustrated when I hear people refer to it as “new” construction, especially when these building materials have been around longer than many of us have been involved in the fire service.

One example of this is the simple gusset plate. The gusset plates we know today, sometimes referred to as “gang nails,” are fabricated by stamping 18-gauge steel. This stamping process leaves short teeth, 3⁄8 inch in length, that are used to penetrate structural members to fasten them together. Although conventional roof framing remained the dominate method for residential roofs for much of North America well into the late 1970s, these lightweight gusset plates were developed in the early 1950s and can be found on lightweight trusses in structures much older than we typically expect. This reaffirms how vital it is that we intimately know the buildings and types of structures that are found in our communities and do not just solely rely on nationwide overviews of construction methods.

Not All Engineered Materials Are Bad

Far too many in the fire service seem to take a generalized approach with regard to engineered construction and subsequently view it all as one and the same. For the most part, engineering has contributed to far less mass in structural components, and this has created legitimate concerns regarding their structural integrity under fire conditions; however, this isn’t the case for everything.

Some “new” construction building materials have been around longer than many of us have been involved in the fire service. One example of this is the simple gusset plate, which was developed in the early 1950s.

Some “new” construction building materials have been around longer than many of us have been involved in the fire service. One example of this is the simple gusset plate, which was developed in the early 1950s.

Some “new” construction building materials have been around longer than many of us have been involved in the fire service. One example of this is the simple gusset plate, which was developed in the early 1950s.

An example of this is glue laminated timber (glulam). Glulam is manufactured using full dimension lumber, most commonly two inches by six inches, and is laminated together using phenol-resorcinol, melamine-urea, melamine, or polyurethane adhesives. The adhesive to lumber ratio in these members is relatively low in comparison to many engineered products. The resulting material is quite strong with considerable mass, and it can withstand the effects of direct flame contact for an extended amount of time. Glulam is as close to traditional heavy timber as we find in the engineered lumber classification, and many fire departments rely heavily on these materials as their route of travel and safe working platform while operating topside. One caveat to this is that, although glulam is very strong, it is still a combustible material and ultimately contributes to the overall fuel load of the structure. In addition to this, because of the way that glulam is assembled using multiple layers of dimensional lumber, tests have shown that once one layer has completely burned away, there is a brief period of renewed fire growth as a result of an unburned surface that is now exposed.

Wood construction is not going anywhere. In fact, we are seeing the industry flourish, especially with the recent push for large mass timber high-rises using cross laminated timber in many major cities. Wood is a staple of the North American construction industry and will always play a significant role in the profession of fighting fires.

Mass Over Math

When taking into consideration all the changes that have occurred in the construction industry, one of the most detrimental factors that affects us as firefighters is the reduction of mass in our structural members. For the most part, mass in structural components increases the fire resistance qualities, which in turn allows us more time to safely and effectively complete our mission of saving lives and protecting property. While engineering has brought many incredible innovations to the construction industry, the use of these engineering principles to reduce the size and weight of structural members has overall contributed to diminished working times inside or on top of a building once the structural components have been compromised by fire.

Glulam is manufactured using full dimension lumber and is laminated together using phenol-resorcinol, melamine-urea, melamine, or polyurethane adhesives. It is as close to traditional heavy timber as we find in the engineered lumber classification.

Glulam is manufactured using full dimension lumber and is laminated together using phenol-resorcinol, melamine-urea, melamine, or polyurethane adhesives. It is as close to traditional heavy timber as we find in the engineered lumber classification.

Glulam is manufactured using full dimension lumber and is laminated together using phenol-resorcinol, melamine-urea, melamine, or polyurethane adhesives. It is as close to traditional heavy timber as we find in the engineered lumber classification.

Another major contributing factor to mass reduction is the role of economics within the construction industry, and this mindset has found its way into many engineering educational institutions. In schools around North America, competitions are held to see who can design theoretical trusses that are the lightest, require the least amount of raw materials, and are the most cost effective. This is the reality of what is occurring within the construction industry, and we need to ensure that we are continuing to educate ourselves on what is happening around us.

Educate Yourself First

Recently, a post made its rounds all over social media that showed an engineered lumber product being used as a replacement for dimensional lumber. The responses to this post varied greatly, but I was surprised by how many immediately jumped to uninformed conclusions regarding the product. Many of the responses referenced the material as being weak, cheap, and highly combustible; the list of negative descriptions went on and on. Although I was already familiar with this product from my time in the construction industry, when I searched for more information it only took about 30 seconds to have the entire technical data specifications for that particular product in front of me. Most engineered products have similar literature available describing the uses, design capabilities, span and load tables, and installation and connection details and will often reference the specific fire and materials testing that the product has undergone. With these types of documents being so readily available, there is no excuse for the amount of misinformation that is being shared throughout the fire service. Social media has become an incredible platform for sharing information, but it can also allow for false information and uneducated opinions to spread like wildfire. It is imperative that we consider everything with a critical approach and further research the areas that we are unfamiliar with, as there will always be incorrect opinions being shared as valid fact.

Ultimately, it is up to the individual firefighters to educate and inform ourselves on new materials and current industry trends if we want to truly understand the impact, both positive and negative, that engineered products have on our built environment.

James Johnson is a firefighter for Vancouver Fire and Rescue Services in Vancouver, British Columbia, Canada. He is assigned to Firehouse 1 and is part of the special operations technical rescue team as well as Canada Task Force One USAR Team. Johnson is a certified fire service instructor II and teaches at the Justice Institute of British Columbia in the fire and safety division. Before becoming a career firefighter, he spent a number of years in the construction industry and completed an apprenticeship and the technical training to become a Red Seal journeyman carpenter. Johnson serves as a technical committee member for NFPA 5000 and is an FDIC presenter.

Pennwell