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With Building Safety Month in full swing, design and construction professionals around the country are looking for ways to ensure their construction sites are as safe as possible. One consideration not to be overlooked is the specification of materials. While safe sites can be achieved with concrete and steel structures, several aspects of mass timber construction make it an ideal choice for maximizing worker safety.

In fact, a recent study performed by the University of Utah’s Integrated Technology in Architecture Center noted safety as a primary benefit conveyed during stakeholder interviews. Among 11 completed mass timber project case studies included in the study, zero safety incidents were reported.

What Is Mass Timber?
Mass timber is an emerging set of engineered wood products commonly used for walls, floors, roofs, partitions and core elements of a building. Examples include glue-laminated timber (glulam), cross-laminated timber (CLT) and nail-laminated timber (NLT).

Different from traditional light-frame wood construction, mass timber products typically consist of several layers of dimension lumber laminated or nailed together to form a new, stronger product. These products have earned praise for their carbon efficiency, cost competitiveness and versatility, and are continuing to gain further acceptance into U.S. building codes.

Mass timber systems allow for safe construction sites for several reasons: the ability to prefabricate large panels offsite, leading to reduced construction duration and easier erection; an installation that does not require the use of a ladder; and the “dry process,” which allows construction to move forward during poor weather.

Mass timber panels are fabricated offsite before being shipped to the construction site, meaning they are able to leverage the advantages of automation and process control. In addition to speed of construction and labor cost benefits, this allows for a reduction of onsite waste, as there are fewer parts to transport and assemble. Because the panels are finished before they reach the construction site, there is less potential for injury because workers are spending less time on installation. As an example, LendLease’s nine-story Forté structure in Australia did not require a single use of a first-aid kit during construction.

Reduced Construction Duration
The University of Utah’s Solid Timber Construction report found a 20 percent reduction in construction duration on average with mass timber over comparable projects that used alternate materials. This is largely due to the ability for foundations and sitework to be constructed simultaneously while the panels are being prefabricated in an offsite factory. Additionally, fewer workers are generally needed onsite to complete the work. Less time spent at the site coupled with fewer laborers means there is less chance for worker injuries to occur.

Safety Considerations
Falls from ladders contribute substantially to construction workplace injuries. According to OSHA, approximately 24,882 injuries and 36 fatalities per year occur as a result of falls on ladders and stairways during construction, with nearly half of those injuries serious enough to require time off of the job.[LA1]  Additionally, a 2011 report from the Centers for Disease Control and Prevention found 81 percent of construction worker fall injuries treated in U.S. emergency departments involved the use of a ladder. [LA2] The typical mass timber construction process does not require the use of a ladder, thus eliminating a major worry for construction teams.

Weather is another concern for construction crews, particularly in areas with harsh winter climates such as the Northeast or Mountain States. While inclement weather can cause many construction sites to become so dangerous they are required to shut down for a period of time, this is not the case when building with mass timber. Primarily, this is because mass timber construction is a “dry process” that doesn’t require welding, which is especially dangerous in a wet environment.

Looking Forward
There is little doubt that mass timber construction will continue to become more prevalent in the United States in the coming years as developers, architects and construction crews gain familiarity with the material and its benefits, and as these systems achieve greater acceptance within U.S. building codes. Last year’s U.S. Tall Wood Building Prize Competition displayed the government’s commitment to advancing the material domestically, as a combined $3 million in prize money was awarded to two tall wood demonstration projects to be built in New York and Portland, Ore. 

The Solid Timber Construction report found requisite knowledge and labor skill in working with mass timber as current obstacles, according to interviews with stakeholders that had prior experience with the material. The continuing growth of mass timber construction should work to alleviate these concerns as more laborers gain experience working with mass timber and broader project teams become more familiar with the process and best practices.

Additional areas for growth include the possibility of enhancing mass timber panels with insulation skin and interior finishes. This would allow for even greater levels of prefabrication, including the potential to create entire modules in the factory, meaning less construction would be necessary onsite.

Ryan E. Smith is an associate professor and director of the Integrated Technology in Architecture Center at the University of Utah and a senior research fellow in the Centre for Offsite Construction at Edinburgh Napier University in Scotland. He also is the immediate past chair of the National Institute of Building Sciences Offsite Construction Council, author of Prefab Architecture and co-author of Building Systems. For more information, email rsmith@arch.utah.edu.

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