Mass Timber for Everyday Projects
By Maria Chesnut, PE, MLSE – In 2010 a Cross-Laminated Timber (CLT) supplier came to my office in the hope of convincing us they were manufacturing the next big thing in construction materials. I was fascinated. I was ready to make CLT (and other Mass Timber framing styles) happen. While I admittedly was much less skeptical a decade ago, this idea stuck: what if we could remove concrete and steel from buildings, embody carbon in them, and then make them easier to build by using tiny sticks of wood? Brilliant!
The lunchtime road show and promise for building better failed to gain immediate traction amongst our building professionals. Change can be slow in our industry, and we all got busy with projects that were designed and constructed using traditional methods.
Seven years later I received an invitation to the International Mass Timber Conference in Portland and I eagerly accepted. The first day was a tour of mass timber buildings in the Portland area. As I walked up the stairs of a partially constructed Carbon 12 building, the tallest mass timber building in the U.S. at that time, the engineers made Mass Timber seem so simple. Then each conference speaker and panelist spoke with passion and hope which excited my structural engineering heart, but left me wondering how could I design more Mass Timber and foster the same excitement in others for the product? What happens when I leave Portland and my fellow Mass Timber enthusiasts? Knowledge, relationship building, and education would have to be my allies.
I learned that the Forest Business Network– the organization that hosts the Mass Timber conference – is not only based in my hometown but was active in a “Mass Timber Rising” group to promote and collaborate its use. Count me in! I also have several awesome colleagues who share my enthusiasm and growth in Mass Timber knowledge. I was not alone.
Visions, talk, discussions are one thing; practical details are something else. Could the regional manufacturing capacity and building code requirements keep pace with my excitement? Maybe there was cause for hesitancy back in 2010. Thankfully, a lot has happened in the last decade to influence how we can use Mass Timber in the U.S. today.
Where We Are Today
Following the trajectory of Mass Timber in the United States and around the world has been fascinating. The record height for the tallest Mass Timber building in the U.S. was broken three times in four years. Mass Timber is becoming a part of our material landscape and to the great benefit of building performance and our environment.
However, coming from a region where our building sizes do not push the limits, the positive attributes of Mass Timber remain and are attainable for many buildings. While we still need faster build times, our recent projects provide benefits like:
- Minimal onsite waste.
- Lighter weight relative to concrete and steel buildings which reduces concrete foundation needs.
- Requires less onsite labor for framing. Sit down with a contractor to talk about labor shortages and you will quickly see how mass timber can help!
- Reduce our carbon footprint.
Morrison-Maierle’s mission is to create an understanding and provide accessibility to mass timber for all architects and owners; it can be used on everyday projects like we design and build here in Montana. Mass Timber is not solely for large-scale projects.
Here are a couple of things I’ve learned as a structural engineer about working on Mass Timber projects that may help you decide if it is right for your next project.
1. Change is Hard, But Solutions are Plentiful
The positive attributes of Mass Timber are numerous, but we all know that change is hard. I mean really hard. We understand the need to balance business stability with the desire to be on the leading edge of advancements, especially when status quo works well. Think about the last time you actively worked to change a habit. Then add money and the feeling of uncertainty on top of that. That “hard-to-adopt” habit, the one you really wish you already had, just got especially difficult.
Since my Mass Timber journey began in 2010, I’ve thought a lot about achieving this balance. I’ve also been asked a wide variety of questions. Some of those that constantly pop up in conversations during the early stages of projects are:
- Is this really going to be faster to frame?
- Will I really need less onsite framing laborers?
- Isn’t this going to be much more expensive?
- We don’t have any direct comparison costs and can’t take a chance on this budget.
- The contractor will throw a high number at this one. How do I prevent that?
- Do I now have to expose all my mechanical ducting and electrical wires?
- Can my project really impact climate change?
When answering these questions, I can already see their next thought forming: “Ahhh! Maybe I should just stick with my conventionally framed building.”
However, in 2021, through an increasing amount of Mass Timber projects in our region, we know more; many contractors have more experience, and we can push the envelope for continuous improvement within our Mass Timber projects. We’re now at a point where we can provide evidence-backed answers to those questions. Mass Timber is adaptable, customizable, and can be used on your everyday projects.
2. Reach Out to Experts
There were several projects over the years where we pressed to use Mass Timber for the building framing system, but the pieces just didn’t click into place or team buy-in was not there. Then, we caught steam. One of our recent projects was the Nez Perce Clearwater Forest Supervisor’s Office in Kamiah, Idaho. We had a meeting early in the project where the use of mass timber was discussed. We did not want to let this amazing opportunity slip through our hands with excitement shared by the design team and owner. So, we had to get to work.
We decided early on as a team that the extent of the Mass Timber framing would be cross-laminated timber (CLT) for the roof framing and elevator shaft and glulam members for the interior support beam lines and columns. The remainder of the walls and mezzanine floor framing would be light wood framing. This decision allowed for mechanical, plumbing, and electrical utilities to run through walls according to conventional practice. We also vetted several panel types, including nail-laminated timber (NLT), dowel-laminated timber (DLT) and CLT. The design at overhangs, product availability and cost estimating with suppliers ultimately help inform our decision.
We typically engage Woodworks and a Mass Timber supplier when we begin each project. For the Supervisor’s Office, we reached out to SmartLam for design assistance. The depth of information with professionals available to help answer questions and talk through design direction is extensive. We want to ensure that we are keeping up with the continuous improvement of the industry. They can utilize their experience from other projects and spread current knowledge around. Knowledge from these entities goes far beyond structure, so I suggest you reach out with questions too.
We were simultaneously working with the architect on the layout for the roof panels and beam/column locations to ensure efficiency in the design. The panel cost increases significantly with each lamination (the thinnest panel is three laminations), so it is critical to strike a balance between maximizing panel span length using the thinnest panel possible and minimizing the number of glulam beam/column bearing lines. Whew! We now had a plan, and everyone was on board!
3. Engineering Efficiencies
One of our greatest advantages at Morrison-Maierle is having all engineering disciplines under one roof. When I want to understand mechanical duct penetrations in the structure, I walk over to my coworker’s desk and talk through it. Mass Timber projects work better with upfront coordination between all trades.
When the panels arrive from the supplier to the job site, most of the duct holes have been cut and ready, the windows are already sized, and the puzzle (with instructions!) is ready to assemble. For example, on the Supervisor’s Office, a small detail that paid off was the electrical engineers realized early on that they would have issues running exposed conduit past large glulam beams. We were able to specify a small notch in the CLT panels at regular intervals over top of the glulam beam to accommodate the conduit. This eliminated the need to drill holes for the conduit in the field and created a better exposed aesthetic.
As a multi-service firm, we are collectively looking out for the best interests of the project, not our individual disciplines, as we understand issues and create solutions. A coordinated effort and drawings are critical to minimizing field time and maximizing construction efficiency.
4. Faster to Frame
Once construction rolled around, it was once again proven that Mass Timber roof panels can indeed be installed much faster than conventional framing methods. The entire mass timber roof package for the Supervisor’s Office was framed in five days with five laborers onsite to run the crane and set the panels. The onsite superintendent commented that he would complete installation in three days if he had a second chance.
On some of our projects, I have taken a deep breath before asking site superintendents their view on the use of Mass Timber framing. Much to my surprise, I have heard comments such as “it was really straightforward” and “it went up so fast.” In the case of the Supervisor’s Office, the contractor also stated that the cost ended up being comparable to traditional wood framing. I look forward to future lessons-learned sessions as we hone the process and work toward getting more responses like these.
Future Projects and Information
We will keep working and encouraging Mass Timber in our everyday applications, and really look forward to the buildings that require us to push the envelope (The College of Forestry Building at The University of Montana will be our next opportunity). There are several factors to consider for each project when it comes to Mass Timber. We can help guide you through this process.
Throughout the next few months we will be posting a series of articles to help answer the questions and success stories from our Mass Timber projects. Mass Timber is attainable for everyday projects. Enjoy and definitely reach out — we are excited to talk about this topic!
Maria Chesnut, PE, MLSE is a senior structural engineer and the Missoula Office Buildings Group Leader. Her range of building types includes commercial office, civic, K-12 schools, higher education, hospital, multi-family, existing building renovation and residential. What Maria enjoys most about her profession is the involvement and impact her work can have on communities. Through project management and leadership, she enjoys cultivating teamwork that creates positive solutions.