The LARK Hotel’s 4-Story Addition, a New CLT Building in BozemanNov 28 2018 · 0 comments · CLT or Cross-Laminated Timber Construction, Hospitality, NISHKIAN MONKS, Wood Frame ·0
Downtown Bozeman’s The LARK boutique hotel recently completed its new 17,600-square-feet, 4-story addition which the hotel is calling its West Building. The LARK hotel is located at the corner of Main Street and Grand Avenue and the addition is adjacent to the current LARK hotel building, a remodel of a traditional motor inn that was featured in our previous article. The new addition expands the hotel to include an additional 29 guest rooms and a ground floor event gallery and commercial space which is currently occupied by Treeline Coffee Roasters.
Operated by Columbia Hospitality, The LARK hotel has now close to 70 guest rooms available, an increase from about 40 rooms prior to the expansion. Designed by ThinkTank Design Group, the 4-story addition is the first hotel building project that employed cross-laminated timber (CLT) construction in Montana. North Fork Builders is the general contractor. Nishkian Monks served as the Structural Engineer of Record on this CLT project.
So, what exactly is CLT?
Cross-Laminated Timber or CLT is an innovative engineered wood developed and used in Europe since the 1990s as an alternative to stone, masonry and concrete construction and is quickly gaining momentum in North America, with many manufacturers now supplying CLT panels. It can be used for roofs, floors and walls of both residential and commercial structures. CLT is essentially mass timber plates made from smaller framing lumber laminated on their wide faces to create a large slab of wood. In North America CLT is typically manufactured in standard 3-, 5-, 7- and 9-ply panels or layers of boards up to 10 feet wide and 64 feet long stacked orthogonally. Non-formaldehyde-based glues are applied between each layer. The entire panel assembly is placed in a large press to produce a dimensionally stable building material, and then cut to exact specifications. This cross lamination provides dimensional strength, stability and rigidity. CLT is sometimes called “super plywood” because it follows the same manufacturing process as plywood and glulam.
CLT panels have great potential for providing cost-effective building solutions for residential, commercial, and institutional buildings in accordance with the International Building Code, and offer numerous benefits, including:
• Design flexibility for single- or multi-story buildings;
• Thermal performance and energy efficiency;
• Negative carbon footprint, renewable and sustainable;
• Minimal jobsite waste and reduces on-site fabrication, plus manufacturers can reuse fabrication scraps for stairs, other architectural elements, or as biofuel;
• Good STC acoustic performance ratings;
• CLT can be used for effective shear wall and diaphragm solutions for lateral loads, whether wind or seismic;
• Provides valuable fire resistance of exposed timber elements because of the ability of mass timber to form a protective layer of char, which protects the remaining structural section in a fire;
• Quick and efficient installation, easy assembly, clean fit and minimize labor. CLT’s precise prefabrication allows for accuracy, reduced demand for skilled workers on site, and reduced installation time which improves efficiency and results in lower capital costs and faster occupancy for accelerated projects.
The LARK’s 4-story addition consists of AHC+Derix CLT panels and glulam beams and columns. The building’s structural system is Type V construction and made effective use of the IBC 2015 Alternate Means and Methods Process to implement CLT panels as a construction material. The floor system of the hotel consisted of CLT panels and glulam beams—5.5-inch of CLT plus a 5-inch layered assembly of lightweight concrete, sound mat, plywood, and a hardwood top layer. This flooring design has delivered superior acoustical performance throughout the building ensuring guests can relax in a quiet setting with minimum noise levels. Here’s a short video showing the installation of a Rothoblaas HBS 8mm x 250mm long screw into a predrilled hole. The walls were constructed with a combination of CLT panels, glulam columns, and conventional stick-framed wood walls. All of the structural components above the foundation were pre-fabricated off-site, which allowed for fast assembly of the structure being built on a site with limited available space (in this case the building area is approximately 120 feet by 60 feet). To view the timelapse video of the CLT walls going up, click here. Prefabrication of the structure also allowed for mechanical, plumbing, sprinklers, and electrical penetrations in the floors to be accurately provided and coordinated prior to construction. The maximum panel size for this project (approximately 10 feet by 40 feet) was limited by the standard dimensions of commercially produced shipping constraints. In order to lift the panels into place, no special rigging was required, only four lifting plates attached to the panels with large screws allow the panels to be placed quickly and easily. Fastening of the exposed framing was performed with large self-tapping screws and concealed structural hangers which provided the load capacity, the required fire resistance, as well as the desired prominent architectural features in the interior. The exposure of the mass timber elements required a 1-hour fire rating (calculated per NDS 2015 methodology), which protects the interior of the structural member to the industry standard for this type of building. The relative rigidity of the CLT panel diaphragm also removed the requirement of exterior shear walls around the perimeter of the building. This provided additional architectural flexibility for windows, doors, and mechanical penetrations throughout the perimeter of the building. Nishkian Monks also served as the primary special inspection agency on this CLT project to help ensure a high level of quality throughout the construction process.
“Our goal was to be more sustainable and efficient in the way that we develop and construct our buildings,” said ThinkTank’s Brian Caldwell at the Timber Tour on October 23. “One of the biggest plusses for wood is that it is renewable and sustainable. Every ton of cement creates a ton of carbon during the manufacturing process while every ton of wood removes two tons of carbon from the atmosphere.”
The intent of CLT is not to replace light-frame construction, but rather to offer a versatile, low-carbon, and cost-competitive wood-based solution that compliments the existing light-frame and heavy timber options while offering a suitable candidate for some applications that would otherwise use concrete, masonry, and steel. CLT utilization in mid-rise building types appears to be growing in popularity as an emerging construction material in Montana and in the rest of the country. The Nishkian team hopes that the example set at The LARK’s 4-story addition will help further the efforts of other building owners and developers to incorporate CLT into their building projects in both the private and public sectors.