Glulam timber is on its way up
In the following Q&A, IMEG structural engineer Alyssa Fee discusses glulam timber and its rise in popularity, especially in projects like 1040 W. Fulton, where owners are looking for a particular aesthetic.
Q: What is glulam? Is it different than cross-laminated timber?
A: Glulam members are glued-laminated timber in which the layers are glued together and with the grain of the wood oriented in the same direction. This helps to produce larger and longer–length members. Glulam has good strength and stiffness properties – it can also be curved and bent – and is typically used for beams and columns. Cross-laminated timber is also made of layers, but the grains alternate at 90-degree angles for each layer. It typically is used for walls, floors, and roofs and has two-way slab spanning capabilities.
Q: Are mass timber options like glulam becoming more popular? If so, why?
A: Yes. Mass timber is becoming very popular for a couple of reasons. Wood is a natural material that attracts people for its green advantage. It’s renewable, and the life cycle of wood has an overall lower impact on the environment than steel and concrete. Many owners also choose mass timber for its aesthetics; wood is a warm and inviting material that architects can leave exposed. This also means less finishes are required in the building – a cost-saving benefit to owners. Glulam also has a natural fire rating (if it meets the minimum code–required sizes for timber elements), so it does not need to be fire proofed or encased in a gypsum enclosure.
Q: Will recent changes regarding fire resistance to the International Building Code have much of an effect on the use of these materials?
A: In IBC, glulam is treated the same as heavy timber when it comes to fire resistance. Heavy timber has natural fire resistance capabilities based on the inherent size of the timber elements. The large members are capable of supporting loads longer than smaller members because a char layer forms on the surface of the heavy timber member that allows the inner layers to remain undamaged. IBC provides minimum dimensions required to meet these requirements.
Q: Are there any new trends or uses for mass timber that owners and architects should know?
A: The biggest advantage to mass timber construction is the environmental advantage over steel and concrete. For wood to become a structural material, it produces less than one-quarter the carbon emissions of either concrete or steel production. This – along with the improvements to the structural capacity of cross-laminated timber, nail–laminated timber, and dowel-laminated timber as wall and floor material – has helped to grow the market. Additionally, new changes expected in IBC 2021 will allow for mass timber structures to be up to 18 stories.