insights | 07.26.21

Erection of a Mass Timber Structure

Erection of a Mass Timber Structure

By Zach Moffitt, Senior Project Manager, Tellepsen

Tellepsen has the great honor of serving as general contractor on the San Jacinto College Mass Timber project. Upon completion in the Fall of 2021, this will be the largest mass timber instructional building in the country.

The purpose of this narrative is to highlight the unique nature of the mass timber structure erection process. Our experience shows that mass timber is not only comparable with steel in terms of time to erect but is also a much safer process.

Steel structure columns and beams typically erect very quickly. However, substantial time spent erecting a steel structure lies within the detailing phase which typically requires large crew sizes for maximum productivity. Mass timber relies on much smaller crew sizes for erection. Standing columns and hanging beams can take more time than a steel structure, but this time is made up with the reduced amount of detailing needed for a mass timber structure.

With steel structures, we rely on the composite concrete slab to provide us with a suitable working surface. On mass timber once a deck is placed, you can immediately work from that surface. The result is the ability to begin overhead MEP rough-in once the next level begins to hang, and not waiting on the concrete slab to begin overhead work. Having the option to start overhead MEP systems while erection is ongoing is another opportunity for further time savings. The key is to coordinate this with your erector in advance to ensure a safe working environment for the MEP trades.

Mass timber erection crews are much smaller than steel crews. On our most recent mass timber project, we were able to erect a 122,000 square foot structure in a timeframe comparable to steel, while utilizing a six-man crew for the entire erection process. The result is a substantially safer working environment without the need for welding and grinding. Anyone who has visited a jobsite during the erection process can agree this is a very noisy and seemingly chaotic environment with multiple crews performing hot work and lifts being made overhead. In mass timber erection, single columns, beams, and decks are hoisted one at a time and pinned in place. It is a very quiet process that almost gives you the impression that you are not making much progress when you are accustomed to the process of steel erection.

Lastly, it is important to discuss damage to the structure that occurs during the erection process. What is so unique about mass timber is the structure itself is a major design element. It is inevitable that during transport, storage, and erection some level of damage may occur to columns and beams. Additionally, there is potential to incur discoloration resulting from water stains from rain during construction. It is important to develop a strategy for repairing damage and discoloration that results in a finished product that meets the original design intent.

There are many benefits to building with mass timber. If properly coordinated and planned the result is a safe and simple process.