Cross-laminated timber (CLT) is reshaping how the construction industry approaches structural building components. This engineered wood product, made from layers of solid lumber boards stacked crosswise and bonded together, delivers dimensional stability, strength, and rigidity that rival traditional materials such as concrete and steel. As the building sector looks for greener, faster, and more cost-effective alternatives, CLT has emerged as a frontrunner. A landmark project in Whitefish, Montana, demonstrates these advantages clearly: the first elevator shaft built with cross-laminated timber saved time and money while reducing the carbon footprint of the structure. Understanding how CLT achieves these outcomes is essential for builders, architects, and developers evaluating modern construction methods. For a broader overview of engineered timber systems, see Structural Timber Engineering Sawn Lumber Glulam Cross Laminated.
What Is Cross-Laminated Timber and How Does It Work?
Cross-laminated timber is a mass timber product fabricated by bonding together several layers of kiln-dried lumber boards at right angles to one another. This crosswise lamination process gives the panel exceptional structural performance in both directions, making it suitable for load-bearing walls, floors, roofs, and even elevator shafts.
Manufacturing Process
The production of CLT follows a precise sequence that ensures consistent quality and performance:
- Lumber is kiln-dried to a specified moisture content, typically between 12 and 15 percent.
- Boards are graded, sorted, and planed to uniform thickness.
- Adhesive is applied to the broad face of each layer.
- Layers are stacked crosswise at 90-degree angles and pressed under hydraulic pressure.
- The finished panel is cut to precise dimensions using CNC machinery, with openings for doors, windows, and services routed at the factory.
The result is a panel that can span large distances, carry substantial loads, and resist racking forces better than conventional timber framing. Because fabrication occurs in a controlled factory environment, quality is consistent and weather delays are eliminated entirely.
Key Material Properties
CLT offers several structural advantages that make it an attractive alternative to concrete masonry units (CMU) and steel:
- High strength-to-weight ratio: CLT is significantly lighter than concrete or steel, reducing foundation loads and allowing for smaller, less expensive footings.
- Two-way span capability: The crosswise lamination allows panels to carry loads in both directions, offering design flexibility.
- Dimensional stability: The alternating grain orientation minimizes swelling, shrinkage, and warping.
- Fire resistance: CLT panels char at a predictable rate during a fire, forming an insulating layer that maintains structural integrity for extended periods.
- Thermal performance: Wood naturally insulates better than concrete or steel, contributing to energy-efficient building envelopes.
For a deeper look at how CLT compares with other structural systems, refer to Cross Laminated Timber in Tall Buildings Material Properties.
Case Study: The First CLT Elevator Shaft in Whitefish, Montana
A multilevel building under construction in Whitefish, Montana, provides a compelling demonstration of CLT’s practical advantages. The project team chose a prefabricated CLT elevator shaft over the conventional concrete masonry unit approach. The results speak directly to the time and cost savings that mass timber can deliver on real construction sites.
Traditional CMU Construction: A Baseline for Comparison
Building an elevator shaft with concrete masonry units is a well-established method, but it comes with significant logistical demands:
- A crew of 8 to 12 workers is required for block laying, mortar mixing, reinforcement placement, and grouting.
- Multiple inspections are needed at various stages to verify reinforcement, alignment, and curing.
- Specialized equipment is required to hoist and position blocks and to pump grout into the wall cavities.
- The curing process alone takes several days before the shaft can support additional loads.
- The total construction timeline for a CMU elevator shaft typically spans 3 weeks from start to finish.
CLT Alternative: Faster Assembly, Smaller Crew
In contrast, the CLT elevator shaft for the Whitefish project was fabricated off-site at the SmartLam facility and delivered to the jobsite ready for installation.
- The shaft panels were manufactured in a climate-controlled facility, with zero impact from weather conditions.
- On-site assembly required only 3 workers and a crane operator.
- The entire shaft was erected in a matter of hours, not days or weeks.
- No curing time was needed; the structure was immediately ready for subsequent trades.
Measurable Results
The difference between the two approaches is substantial. The table below summarizes the key comparison points:
| Factor | Traditional CMU Shaft | CLT Shaft (SmartLam) |
|---|---|---|
| Crew size | 8 to 12 workers | 3 workers plus crane operator |
| Construction timeline | Approximately 3 weeks | A matter of hours |
| Weather dependency | High (masonry cannot be placed in rain or freezing temperatures) | None (prefabricated indoors) |
| Inspections required | Multiple stages | Minimal (factory quality control) |
| Relative cost | Baseline | 70 to 75 percent of conventional methods |
| Time savings | Baseline | Nearly 3 weeks saved |
The project demonstrated that a CLT modular structure costs roughly 70 to 75 percent of what a conventional CMU shaft would have required, while compressing the schedule by nearly 3 weeks. These savings came without any compromise on structural performance or building code compliance.
Sustainability Benefits of Cross-Laminated Timber in Building Construction
Beyond the schedule and budget advantages, CLT offers significant environmental benefits that align with the construction industry’s growing emphasis on sustainable building practices. Concrete production alone accounts for roughly 5 percent of global carbon dioxide emissions, and according to the US Green Building Council, 40 percent of national CO2 emissions come from buildings. Replacing concrete and steel with wood as a structural material can have a measurable impact on reducing these emissions.
Renewable and Certified Sustainable Sourcing
Wood is the only major structural building material that is renewable. Unlike concrete, steel, or masonry, which deplete finite mineral reserves, timber can be regrown in managed forests. CLT manufacturers such as SmartLam procure lumber from sawmills that practice certified sustainable forestry, with third-party certification programs verifying the product’s sustainably managed origins. This chain-of-custody approach gives builders confidence that their material choices support responsible forest stewardship.
Low Embodied Energy
Embodied energy refers to the total energy required to extract, process, manufacture, transport, construct, and maintain a building material over its lifecycle. Wood products consistently demonstrate lower embodied energy compared to concrete and steel:
- Harvesting and milling timber requires substantially less energy than mining, refining, and manufacturing steel or cement.
- Transportation energy is lower because timber is lighter than concrete or steel per unit of structural capacity.
- On-site construction energy is reduced because CLT panels are prefabricated and require less equipment and fewer labor hours to install.
- End-of-life energy is minimized because wood can be reused, recycled, or used as biomass energy, whereas concrete and steel require energy-intensive recycling or landfilling.
Carbon Sequestration
Wood acts as a carbon sink. As trees grow, they absorb CO2 from the atmosphere and store the carbon in their fiber. When that wood is used in long-lived building products such as CLT panels, the carbon remains sequestered for the life of the building. This makes CLT one of the few structural materials that can reduce atmospheric carbon rather than add to it. For more on CLT’s environmental profile, see Cross Laminated Timber.
Practical Considerations for Specifying CLT in Building Projects
For construction professionals considering CLT for their next project, several practical factors deserve attention during the planning and specification phase. These considerations apply whether the application is an elevator shaft, a load-bearing wall, or an entire building structure.
Design and Engineering Coordination
CLT projects require close coordination between the design team, structural engineer, and CLT fabricator early in the process. Key steps include:
- Engage the CLT manufacturer during schematic design to confirm panel sizes, layup configurations, and connection details.
- Produce a detailed shop drawing set that includes all openings, penetrations, and attachment points.
- Coordinate mechanical, electrical, and plumbing routings before panel fabrication to minimize field modifications.
- Plan the lifting sequence and crane placement based on panel weights and site logistics.
- Specify the adhesive type and panel grade to match fire-resistance rating requirements and exposure conditions.
Cost and Schedule Planning
The Whitefish project demonstrated that CLT can deliver significant cost savings, but the exact savings depend on project-specific factors:
- Material cost: CLT panels carry a higher per-unit material cost than CMU blocks, but the installed cost is lower due to reduced labor, equipment, and inspection requirements.
- Schedule compression: Faster installation reduces general conditions costs, including site overhead, temporary utilities, and equipment rental.
- Foundation savings: The lighter weight of CLT can reduce foundation and footing requirements, generating additional savings.
- Financing costs: Shorter construction timelines reduce interest on construction loans and get the building into service sooner.
Planning Checklist for CLT Projects
| Phase | Action Item | Responsible Party |
|---|---|---|
| Pre-design | Evaluate CLT feasibility for the specific application | Owner, architect |
| Schematic design | Engage CLT manufacturer for preliminary sizing | Architect, structural engineer |
| Design development | Complete shop drawings with all openings and MEP coordination | CLT manufacturer, MEP engineer |
| Pre-construction | Plan crane access, panel staging, and erection sequence | General contractor, CLT erector |
| Construction | Install panels per approved sequence with quality inspections | CLT erector, site superintendent |
| Post-installation | Protect exposed CLT from moisture during subsequent trades | General contractor |
For a broader perspective on how mass timber and other advanced materials are changing building construction, see Advanced Construction Materials Fiber Reinforced Polymers Mass Timber.
Conclusion
The first elevator shaft built with cross-laminated timber in Whitefish, Montana, proves that CLT is not just an environmentally responsible choice but also a practical one. With a cost of 70 to 75 percent of conventional methods, a reduction in crew size from 12 workers to just 4, and a schedule savings of nearly 3 weeks, the project makes a strong business case for adopting mass timber in vertical construction applications. As the building industry continues to seek ways to lower embodied carbon, reduce construction timelines, and control costs, cross-laminated timber is positioned to play an increasingly important role. Builders and designers who understand the material properties, installation process, and sustainability advantages of CLT will be well equipped to specify it effectively on their next project.