Cross-laminated timber (CLT) buildings are poised to become a more familiar face in our local communities in the coming year.
In an era where consumers are constantly connected to technology, and a world that’s overwhelmed by the daunting challenge of global warming, the desire to reconnect with tangible, high-quality products is at an all-time high. Commercial building owners and tenants everywhere are seeking the look and feel of old materials — the natural warmth that historic brick and timber buildings provide. Unfortunately, getting that look isn’t always easy unless a building has beautiful bones, is in the right neighborhood, and just waiting to be restored. What if the built environment could offer a reduced carbon footprint, be on the cutting edge of technology and also reflect the “craft” quality of natural materials that we so desire? While not a new method of construction, cross-aminated timber (CLT) buildings are poised to become a more familiar face in our local communities in the coming year.
With the market demanding new and existing buildings that are unique, sustainable and provide users with qualities they can’t find elsewhere, it’s easy to see why architects and designers are interested in investigating the use of CLT. This uniqueness, particularly in commercial buildings, may help owners command premium lease rates.
While wood is a commonly used material, it is not a typical method of construction for buildings over four stories. Advancements in wood technology and manufacturing have been realized in CLT (engineered wood panels laminated together in alternating directions to enhance strength) making tall wood buildings not only possible, but safe and cost effective. Today, engineered wood components can include glulam columns and beams, and laminated timber for floor assemblies, cores, vertical wall panels and highly visible features like stairs.
As architects, the look of CLT has captured our imagination because of its inherent beauty and authenticity, as well as the opportunity to provide a built solution that reduces our carbon footprint and demonstrates the same performance standards as steel or concrete.
CLT is precision engineered and factory manufactured to exceptional levels of accuracy, often using CNC (computer numerical control) machines.
This level of precision improves speed of delivery, construction time, reduces waste, and has the potential to reduce cost – all valuable benefits to the building owner.
OZ Architecture is currently designing two commercial CLT buildings in Boulder and Denver, Colorado, and has completed one residential home in West Virginia. The material has provided many design opportunities and challenges. Here are four things to consider when looking at CLT for your next project:
1. Structure is beautiful, expose it – A prime driver of design in a CLT building is often to expose as much timber as possible in the walls, ceilings and columns. This warm and beautiful material can reduce later add-on’s like dropped ceilings, wall coverings and drywall.
As a commercial building owner, this has the potential to add long-term value to the investment by minimizing future build-out costs.
2. Non-traditional column grids are OK – One possible limitation of CLT is the maximum size available for the design team (approximately 10 feet wide by 40 feet long by +/- 1 foot thick). This size limitation is also influenced by transportation – what can fit in a shipping container or on a flatbed truck – and can lead to a denser column grid layout in commercial buildings than a concrete or steel structure would provide.
One strategy is to treat the grid the same way you would treat the exterior window patterning (accommodating standard office or workstation dimensions) but allowing the exposed columns to enhance the design.
3. Think “beyond sustainable” – From the reduced carbon footprint to sustainable forestry practices, CLT is one of the greenest methods of construction available.
Trees are a 100 percent renewable resource and CLT is typically harvested from young, small-diameter trees such as spruce, Douglas Fir and larch. CLT generates less greenhouse gas emissions than traditional construction types, reducing the buildings’ overall carbon footprint.
4. Test alternative systems – Maintaining an exposed structure requires the design team to be innovative in mechanical, plumbing and electrical systems layout to allow for maximum flexibility as the interior plan changes.
Because CLT arrives to the job site cut to size, one solution is to pre-route knockout panels to accommodate electrical distribution. On the mechanical side, unique systems such as chilled beams can be tested given the end-user, but overall it’s important to plan ahead so that minimum clear heights can still be maintained with exposed ductwork throughout.
The greatest challenge of using CLT isn’t the design or engineering but managing public perceptions and educating the construction industry about a currently unfamiliar method.
There is no question that CLT is a beautiful material; the quality and richness it provides is an exciting opportunity for new American construction. If a building using CLT can be executed in a way that doesn’t impact cost, then it is certain to be the next big thing. In the meantime, it appears to be worth a slight premium to be on the forefront of this up-and-coming trend in architecture and design.
AMANDA JOHNSON is an associate principal at OZ Architecture, a top-tier design and architecture firm based in Denver with a 50-yearhistory