We’re letting you in on a secret: When it comes to the design of new construction materials, don’t assume that the product manufacturer, or anyone else, is making sure that the “new thing” will perform just as good or better than the old thing.
Even if you are told the new thing complies with the building code and is the best thing since sliced bread, don’t believe the hype. In fact, watch your back and take a common sense, cautious approach when selecting and using new materials.
We have some tips to help you with that approach, and to help you out of a jam if the project goes bad because of the use of new materials.
A Better Approach
In his article, “Rainwater Intrusion in Light-Frame Building Walls,” which describes how to minimize the risk of water-intrusion damages, U.S. Forest Service research scientist Charles Carll calls for the adoption of an “engineering approach” to the building codes. His idea is to define, prescriptively, how a building envelope should be assembled, which will dictate how it should perform.
The key, according to Carll, is for code officials to take a holistic approach to the assessment of the envelope. This is because, under the current building-code scheme, design professionals and contractors are free to approach design and construction based on their respective experience, and in reference to the manufacturer’s recommendations. Under the current approach, Carll says, some will get it right while others will be totally off the mark.
For example, some weather-management concepts are relatively easy to understand, such as how to flash a roof to prevent water from entering around a chimney. Other concepts, like “vapor drive” through the wall, are much more elusive, especially considering how airtight modern buildings are designed and built in order to conform to energy codes. For these reasons, Carll recommends that the building-code officials do the math and science to figure out the big picture.
Beyond Building Codes
In surveying the building-science literature, Carll sounds a cautionary note regarding the current role of the code officials. It turns out that code officials are much more concerned about structural safety issues and less concerned with water intrusion. This is because of the perception that the damages resulting from water intrusion are simply “economic issues.” To the code officials, leakage will be obvious before much damage occurs, and if chronic water intrusion causes structural damage, some sign of the damage will appear before it poses a safety hazard.
Carll points out that the construction-materials industry isn’t all that concerned about the details either, because there are just too many variables for industry to address: “Manufacturer’s instructions and drawings are almost always incomplete because of the considerable variation in materials and architectural features with which a given product may interface.”
And even though Carll posits that industry would greatly benefit from code-imposed standards—because an accepted standard of care creates a more predictable marketplace and affords greater protection from legal liability—it turns out that most product manufacturers just don’t want to bother with the heavy lifting.
So, the buck keeps getting passed. Manufacturers assume that code officials, design professionals, or someone else will take the lead and provide guidance on how to properly integrate the envelope, while code officials have more important things to worry about. Meanwhile, design professionals and contractors assume the manufacturers or code officials are minding the outcome.
And so product sales personnel will pitch that the new thing is certified code compliant—it has an evaluation report and everything. The smart shopper, however, should know to look behind the curtain.
The Way it Works
Code approval for using the new thing is obtained through an evaluation report issued by the ICC-ES or some other approved evaluation service. These reports certify that the new thing is code compliant so long as it is manufactured and installed in strict accordance with the requirements of the report. While these reports do address the code-mandated quality, strength, effectiveness, fire resistance, durability, and safety requirements, they generally do not require a holistic analysis of how the new thing will work when integrated with other building components.
To borrow on Carll’s theory, a holistic assessment approach would benefit consumers of all new construction materials, regardless of code approval. A recent cautionary tale on this point can be found in the structural failure of a Cross Laminated Timber (CLT) project at Oregon State University (OSU).
A Look at CLT
CLT is one of the hottest construction materials in the marketplace. They are engineered wood panels that can be used as a walls, floors, or ceilings. They consist of several layers of lumber, such as 2x6 boards, which are stacked in alternating directions, bonded with adhesives, and pressed tight to form panels.
Panel dimensions depend on the size of equipment owned by the CLT manufacturer, although it is common to see panels that are 12 to 18 inches thick, by 10 feet wide, by 40 feet long.
A popular use of CLT is to erect tall wood structures. In fact, Canada recently changed its building codes to allow for 12-story CLT buildings, doubling the prior limit. This product has attracted so much excitement that, now, an entire mass timber district is being developed in Toronto. There are also many prominent CLT projects being developed throughout the U.S.
It is important to note that this article is not critical of CLT as a material, and, for what it’s worth, the authors like the aesthetic and support the logic behind using CLT. The point is that, ideally, the industry should think through the process and work out the kinks before products go to market. Since industry isn’t, designers and contractors should proceed with open eyes.
A Bad Day at OSU
The OSU failure failure involved a CLT floor panel—30 feet by four feet, equating to about a thousand pounds of material—that came unglued and crashed 14 feet from the third to the second floor of the building. Thankfully, no one was injured. During the investigation, it was discovered that the failure resulted from an unregulated manufacturing process. A process change was made by the manufacturer to heat the wood boards before gluing them. This resulted in poor bonding between the adhesive and the wood layers.
It turns out that the American Plywood Association (APA), which certifies CLT fabricators based on its PRG 320 standard, only regulates performance criteria for the CLT product itself; not the manufacturing process. Quoted in the Engineering News-Record after the OSU incident, BJ Yeh, director of APA’s technical services division, said PRG 320 does not address preheating the wood, and that performance standards “do not get into that kind of detail.” He said engineered products are not suitable for a prescriptive standard because each mill has its own, slightly different production method.
So, one must ask, if the APA does not regulate the CLT manufacturing process, then who does?
Some Gaps in the CLT Universe
New information is coming to light on the integration and use of CLT, even though the product has been in use in the U.S. for about nine years and in Europe for about 25 years. Academics and industry are currently exploring solutions for proper anchoring of CLT to concrete, and for the waterproofing of CLT at the interface with concrete.
More significantly, research is being performed on the unknown effects of prolonged moisture exposure to CLT, which may occur during construction. A recent Construction and Building Materials article, entitled “Manufactured Structural Timber Building Materials and Their Durability,” finds that prolonged rain leakage or moisture exposure during construction could pose considerable concern for the durability of CLT products, as well as for LVL (Laminated Veneer Lumber) and OSB (Oriented Strand Board) products. The article states:
“The results [of the study] showed untreated OSB and CLT were very susceptible to decay. In comparison, LVL was less susceptible. Testing conducted on CLT using surface application of boron preservative prevented decay. Further work is needed to understand the full extent of moisture ingress in wooden panels during construction and service of the multi-story buildings and improving the durability of panel products.”
Another concern raised by a vice president of a prominent property insurer’s underwriting department is how to define the appropriate repair scope for CLT buildings after they are exposed to heat from a fire. For example, if a kitchen fire occurs within a unit in a multi-story CLT building, can the unit be repaired in place or does the building or some part of it need to be disassembled and rebuilt? The concern comes from the fact that the panels are assembled with adhesives, as opposed to traditional steel fasteners, and the impact of heat on the adhesive bond has not been thoroughly vetted. Apparently, there is no consensus answer to this question.
One significant benefit of using CLT is a lighter carbon footprint. The 18-story Brock Commons CLT tower in Vancouver, British Columbia is credited with having significantly less of an environmental impact than a comparable steel and concrete structure, offsetting an estimated 2,432 metric tons of carbon. While minimizing a project’s environmental footprint is a laudable goal, designers and users of CLT should approach their projects with inquisitive minds and open eyes.
The Bottom Line
The takeaway for design professionals and contractors is to identify the unknowns and to approach new products with a healthy dose of caution and a diligent assessment. There is no perfect solution, however, in our research, we find that the National Association of Home Builders provides an elegant guide for evaluating new products, called Assessing Building Materials. The guide poses simple yet thoughtful questions in a check-box assessment format about how new products should be evaluated (Readers may email author Jack Levy at jack@theGLB.com for a copy of the guide).
Conscientious design professionals and contractors should adopt this kind of evaluative methodology and should also be mindful that the knowledge they seek and information they need may not yet exist. In the end, if there are too many holes in the analysis, then that should be seen as a sign.
If you unfortunately wind up in a claim situation involving a potentially defective manufactured building product, the following tactics have proven very useful in past cases:
• Subpoena the ICC-ES, or other evaluation service, for all communications involved in developing the evaluation report. What the manufacturer represented to the evaluation service may be different than what it represents to the market.
• Carefully compare the product approved in the report against the product being marketed. Modifications adopted by the manufacturer after reports are issued do not always go back to the evaluation service for further assessment and approval, though they should.
• Compare the composition of the samples given to the evaluation service for assessment versus the composition of materials being sold in the market. The mix of elements used to manufacture composite materials (more or less resin, more or less filler) sometimes change.
• Evaluate whether the stated testing criteria are appropriate. Manufacturers may list generic instead of specific testing standards in product literature, or otherwise disregard or not test based on appropriate testing standards.
A little focused digging can go a long way, especially considering that product manufacturers tend to take hard lines in litigation for fear that payment on claims will take them down a slippery slope.
Since the building officials and industry won’t take the laboring oar to evaluate all of the pitfalls, design professionals and contractors really do need to be on guard. Of course, there are always the “Plan B” considerations, which you may have heard before:
• Use written contracts and include pass-through indemnity provisions.
• Obtain additional insurance from subcontractors and material suppliers (written into the purchase orders) to be afforded on a primary and non-contributory basis.
• Consider limitation of liability provisions in sales contracts.
“Plan A” should be to take good care to build a better project. Your business and outlook on life will improve, and you’ll be time and money ahead if you don’t have to hang out with those of us in the claims universe.