Perlo has seen its fair share of different materials used across all sorts of projects. With lumber prices heading in an upward trend and an emphasis on environmental responsibility, Cross laminated timber (CLT) in recent years has risen in popularity and we see it first-hand with our clients. Cross laminated timber is a more sustainable wood product with great structural integrity that can be used for floors, walls, and roof structures. The product has made waves in the news for its use in multi-story buildings, such as Portland’s Albina Yard project, but the uses for this sustainably sourced wood product are nearly endless.
Today we will explore more about what CLT is, and how it can be used to enhance the building construction process and create aesthetically pleasing spaces.
What is Cross Laminated Timber?
Cross laminated timber is a pre-engineered wood panel made up of lumber that is laid crosswise in an odd number of layers (typically 3, 5 or 7) and glued into place. The panels are produced to custom widths, lengths and thicknesses depending on every individual project’s needs.
Produced by a variety of suppliers across the world, the lumber used to create each board is sourced from trees in sustainably managed forests and from trees that are small to medium in diameter. This allows manufacturers to source their raw materials from forests that can be regenerated.
Computer Numerical Controlled (CNC) machines cut each panel to size and also include any window or door openings, as well as other penetrations. These cuts are incredibly precise and allow for cutting and routing of great complexity. CLT panels are prefabricated and custom sized before shipping to each site, and are lifted into place with heavy equipment.
Cross laminated timber has exceptional acoustic, fire, seismic and thermal performance ratings, and is used for structural elements because of its load bearing capacity. It can even span distances up to 98 feet.
Image courtesy of Think Wood.
How is Cross Laminated Timber used?
The structural applications for CLT are nearly endless, with the panels used for floors, walls and roof structures. CLT can be installed and left exposed for interior applications, and sealed or otherwise finished for exterior structures. A sister product, the Glulam beam, is used in spaces where appearance is important, such as in large, vaulted ceilings, or architecturally attractive spaces like churches, higher education, trendy office spaces or entertainment venues. Glulams work as trusses or purlins and are often paired with CLT panels to span long distances.
The use of wood is often considered to contribute to a warm, home-like atmosphere, and is visually pleasing. In short, CLT can be used for structural systems, for aesthetic reasons or a combination of both.
Alternative Uses for Cross Laminated Timber
Perlo has completed a few projects with CLT as a major component of the work, in applications such as office mezzanines, grocery stores and interior office walls and platforms. These systems can be one component of sustainable building projects that are trying to attain LEED, Living Building Challenge or other green construction accreditations.
In addition to the sustainability component, CLT can be used to achieve:
- Clean installations of mezzanines in existing spaces
- Large clear spans
- Interior prefabricated wall systems
- Lower costs of labor
- Shorter lead times for structural components as compared to steel
Cross laminated timber does not have to be a main component of the project to be effectively utilized. It may simply be a small part of a larger construction project.
Projects with Cross Laminated Timber Components
Young’s Market Mezzanine
The Young’s Market tenant improvement included a new, 3,000 SF CLT mezzanine with exposed glulam beams and timber posts. The use of this material aided in creating a rustic feel, with lighting, ductwork and sprinklers all exposed at the underside of the deck.
The CLT mezzanine was fully installed in only two days. It was then prepped for a 1.5” gypcrete topping slab and sound mat below the gypcrete to reduce sound transmission. In hindsight, the team realized that the gypcrete was likely not necessary. However, it should be noted that the CLT wood is relatively soft as compared to a hardwood flooring product, so it is possible that if the surface is left exposed to foot traffic, it will scuff and scar quite easily. Another benefit to the CLT mezzanine was that the installation of the gypcrete floor was simpler than a more typical tongue and groove structure, or even a metal decking. The CLT board has fewer penetrations where the gypcrete could potentially leak through from the second to the first floor. This factor sped up the preparation time and lessened the materials required for the gypcrete pour.
The final product is a space that feels warm for its occupants, is aesthetically pleasing and highly functional.
DWFritz World Headquarters
This multi-phase, two-story office tenant improvement for DWFritz included a wide variety of CLT panels for walls, mezzanines, stairs and floors. This unique office design was constructed inside of an existing concrete tilt-up warehouse. Each office space was constructed with CLT walls that were left exposed. Additionally, the new space included a viewing mezzanine, stairs, a raised floor and planter boxes made from CLT panels.
Significant planning was involved in the design, review process, transportation and delivery of the panels for this building. All penetrations had to be planned for and pre-cut with the CNC machines at the mill. Routing was completed to accommodate steel stair nosings and the steel track that anchored the wall panels to the floor. The CLT panels were installed prior to many of the finishes being completed, as the space had casework, drywall and furniture, along with mechanical, electrical and plumbing systems that could not be installed prior to the wall installation. The construction teams had to take great care to protect the finished surfaces of the CLT during construction.
As discussed earlier, the finished surface of CLT panels is quite soft and susceptible to damage. To combat this, our teams left the tight wrapping that is used for shipping intact as much as possible until all work was done. Upon completion, the space was unique, beautiful and conveyed a rustic, industrial but still warm feeling for its occupants.
More Advantages of Cross Laminated Timber
In our current climate, CLT has come to the forefront of discussions for use in projects due to its availability, sustainability, and relatively short lead times. Pricing of steel structural components and framing lead times have become excessively volatile, with costs rising sometimes 10% – 20% month over month, and lead times extending out 4 – 5 times longer than the norm. We are fast approaching a place in time where CLT is quicker to get onsite and coming closer to being comparable in cost.
Cross laminated timber has not been commonly used for roof structures in the United States, especially on large industrial buildings. However, we anticipate that this will soon change. Lead times for steel joists and girders have increased to 9+ months from the time of order. This delay in availability isn’t acceptable to meet many project schedules. While the use of a CLT roof structure is still a cost premium, it is more readily available within a reasonable timeline.
We look forward to seeing more creative uses of CLT in future buildings. The structural advantages, warm aesthetic appeal and sustainable sourcing of the material make it an ideal choice for many building components. If you’re considering a new building or interior tenant improvement, we can help to evaluate the options for materials and components that will make the most sense for your space. Contact our team for more information!