If you have been a firefighter for very long, you are probably aware of firefighter’s concerns with engineered wood and how it performs under fire conditions. The use of engineered wood products has grown significantly in recent decades. According to APA–The Engineered Wood Products Association, engineered wood components saw their first commercialization in the 1960s but didn’t enjoy widespread use until the 1980s. (1) Since then, production has increased more than ten-fold, with the U.S. and Canada combining for 1.28 billion linear feet of engineered components in 2004, at the peak of the housing boom.
So What is Engineered Wood? (2)
Engineered wood, also called composite wood, man-made wood, or manufactured board, includes a range of derivative wood products which are manufactured by binding or fixing the strands, particles, fibers, or veneers or boards of wood, together with adhesives, or other methods of fixation to form composite materials. These products are engineered to precise design specifications which are tested to meet national or international standards. Engineered wood products are used in a variety of applications, from home construction to commercial buildings to industrial products. The products can be used for joists and beams that replace steel in many building projects.
Typically, engineered wood products are made from the same hardwoods and softwoods used to manufacture lumber. Sawmill scraps and other wood waste can be used for engineered wood composed of wood particles or fibers, but whole logs are usually used for veneers, such as plywood, or particle board.
As I said earlier engineered wood has been on the the fire service radar for awhile now, so you are probably asking yourself what is the purpose of this article?
Thanks to my good friend Eric Rissman who sent a very interesting Facebook link (3) from Sherwood Lumber. What caught my attention in this post was the way engineered wood products are being used in wall systems for the entire structural frame.
So I did a little digging to hopefully shed some light on how engineered wood products can be used in place of traditional wood framing.
Structural Composite Lumber Basics:
Structural composite lumber (SCL), which includes laminated veneer lumber (LVL), parallel strand lumber (PSL), laminated strand lumber (LSL) and oriented strand lumber (OSL), is a family of engineered wood products created by layering dried and graded wood veneers, strands or flakes with moisture resistant adhesive, into blocks of material known as billets, which are subsequently resawn into specified sizes. (4)
How Is It Made: LP® SolidStart® LSL video
In this article I have focused on engineered wood being used in structural walls, because, I am not aware of any full scale fire service testing that has been done on engineered wood being used vertically or used as a wall. Thanks to the great work from Under Writers Laboratory (UL) (4) and NIOSH (5), we will take a look at some of the highlights from the UL floor and roof testing,that could also pertain to these products and this application.
UL TEST HIGHLIGHTS (6)
While most of the 100-plus page UL report on the testing of lightweight building components focused on engineering calculations, several key points emerged to clarify the fire performance of engineered wood components, including:
- Deflection Times:
Although a computer model predicted that the test floor assembly using engineered I-joists would retain its strength longer during a fire than the traditional wood platform, the opposite was the case. Furthermore, the engineered wood supports began to fail and deflect almost from the start of the test and proceeded to degrade in stages, leading to floor vibration, noise, collapse, and burn-through.
The rate at which engineered wood and traditional wood chars is similar. However, because of the very thin cross section of the I-beams, the report found that this charring rate poses immediate dangers to the mechanical integrity of the structure.
- Heat Sensitivity:
Oriented strand board beam sections exhibited initial charring at a much lower temperature than traditional wood, making it impossible to further test some properties of the material.
- Heat Conduction:
Due to compressed plies and binding material, the engineered samples conducted heat faster than other wood samples.
Engineered wood product samples exhibited increased brittleness and loss of mechanical strength compared with traditional wood components when heated in an oven, even without being exposed to fire. Researchers suggested this was due to separation of the constituent compressed fibers under mechanical and heat stress
This is just one of many ways our built-in environment is constantly changing and we need to be a student of our profession, more than ever before. It simply is not enough to “Put the Wet Stuff on the Red Stuff”. We must know that the buildings of today are not going to be built fire safe, and as fire service professionals, we must push for home fire sprinklers to save the lives of those we swore to protect.
Please share this with all your brothers and sisters in the fire service in order to continue raising the awareness of engineered lumber products that we will face in future fire fights.