HCLT Advancements and What They Mean for the Hardwood Industry

By AMANDA BOUTWELL

Looking through our Hardwood Matters archives, we can see that HCLT (Hardwood Cross Laminated Timber) has been a popular and well-researched topic of interest. While it has been several years since we last wrote about HCLT, now is a great time to revisit the concept. There have been many advances in the technology as it continues to inch closer and closer to being a viable hardwood product.

The best place to start is by explaining what HCLT is. At its very basic, Hardwood Cross Laminated Timber is an engineered wood product created when timber planks are laid perpendicular to one another and glued together to form stiff, strong, and stable panels. HCLT is stronger than steel and concrete but holds a beautiful wood aesthetic.

According to Dr. Henry Quesada, Assistant Director of Extension and ANR Program Leader at Purdue University, “CLT is special because of the many pieces of lumber that go into a single panel. A few years ago, we were able to build structures that were about 3-5 stories. But today, construction with CLT can go even higher!”

Unfortunately, this can only be said about softwood CLT because the current standard is based solely on softwood species. The standard, called PRG 320, is overseen by the American Plywood Association (APA). The standard was updated three times in recent years (in 2015, 2017, and 2019) to add various lumber species, but hardwoods were not included. This is likely because traditionally, softwood has been used for structural applications, while hardwoods have been used mainly for flooring, furniture, molding, pallets, millwork, etc.

Dr. Quesada continues, “We will have to change the PRG 320 CLT standard to admit certain hardwood species. The good news is that we already have the rules to grade hardwood for structural applications. Still, these rules are rarely used because hardwood manufacturers can make more money selling hardwoods for appearance applications than for structural applications.”

Henry points out, “Hardwoods can compete in the CLT market using lower-grade lumber. We have researched Hardwood CLT using yellow poplar because it is one of the most abundant species in North America. It is also easy to glue the layers (we can use the same formulations that they use for Southern Yellow Pine). But most importantly, it is economically feasible. Yellow Poplar can compete with the prices of Southern Yellow Pine.

The answer to how hardwood lumber can get into the CLT market is yellow poplar. Could it really be as simple as that? Not quite, but we are on the correct path. Dr. Quesada tells us, “Right now, advocates are working on getting yellow poplar accepted by the APA. Once it is accepted, we can start thinking about other hardwood species. Like soft maple, for instance.”

Dr. Quesada and Sailesh Adhikari (with Virginia Tech) recently published a research paper talking about HCLT, with Henry saying, “In an effort to

Above: Exterior view of MultiPly from the Sackler Courtyard.

Left: Murray Grove exterior, London, UK, 2009. Photo: Murray Grove, a 9-story residential building designed by Waugh Thistleton Architects, was the world’s first multi-story building to have load-bearing walls, floor slabs, stairs, and elevator cores constructed entirely out of mass timber.

There is so much we have working in our favor that the promotion of HCLT won’t be difficult, mainly because it is good for the environment.

Dr. Henry Quesada will host a discussion panel at the 2022 NHLA Convention and Exhibit Showcase, September 21-23 in Cleveland, Ohio. The panel will feature several different perspectives on hardwood CLT, including manufacturing, supply, research, international markets, and more.

get Hardwood CLT to happen, the first thing we did was create HCLT panels made of yellow poplar. Those panels were shipped to Tacoma, Washington, where the APA served as a third-party agency as the panels were tested. We have now moved on to the second step, a combined effort of Purdue University and Virginia Tech. We are using all the information we gathered in our tests to have Yellow Poplar admitted into the PRG 320 standard. This will take a year, maybe two. We have already had discussions with APA, and they are awaiting our paperwork. Tom Inman with Appalachian Hardwood Manufacturing Inc. (AHMI) wrote the change proposal. Now, we are working on finding the needed information to complete the necessary forms and move forward.”

It is likely that HCLT (using Yellow Poplar) will be a marketable product within two years, and architects and engineers in the US and Europe are already working on demonstration projects. Still, the hardwood industry will have to do its part in promoting HCLT to succeed.

There is so much we have working in our favor that the promotion of HCLT won’t be difficult, mainly because it is good for the environment. An April report on climate change, released by the United Nations, indicated that, “harmful carbon emissions have never been higher in human history.” HCLT, like any other hardwood product, sequesters carbon. Every tree in the forest is a carbon sequestration machine. So, the more wood we use, the more trees we can grow, and the more carbon that gets sequestered. It’s a win-win. Now with