Mass Timber Construction
Large engineered wood panels and beams used as structural frames and floors.
Quick Answer
Mass timber construction is a building method that uses large, solid engineered wood members, such as cross-laminated timber panels, glue-laminated beams, and nail- or dowel-laminated timber, as the structural frame, floors, and walls. Elements are prefabricated off site, then assembled, and the code recognizes dedicated mass timber construction types.
The Full Picture
Mass timber refers to a family of structural products made by bonding or fastening layers of lumber into large, dimensionally stable members. Common products include cross-laminated timber (CLT), glue-laminated timber (glulam), nail-laminated and dowel-laminated timber, mass plywood panels, and laminated veneer lumber. Together they allow wood to be used for floors, walls, columns, and beams at scales that dimensional lumber framing cannot reach.
Mechanically, mass timber buildings are typically engineered as panelized or post-and-beam systems. Elements are cut by CNC machines in a factory, shipped to the site with openings, connection pockets, and penetrations already formed, and craned into place. Connections are usually steel plates, screws, and brackets, and floor systems often include a concrete or other topping for acoustics, stiffness, and fire performance.
Fire safety is addressed by design rather than by avoiding wood. Large timber sections char at a predictable rate, and the unburned core keeps carrying load. Since the 2021 International Building Code, mass timber has had its own construction types, IV-A, IV-B, and IV-C, which allow taller and larger buildings depending on how much of the timber is protected by gypsum board or other noncombustible covering. Local amendments and adopted code editions still govern.
For contractors, the delivery process differs from conventional framing. Shop drawings, fabrication lead times, sequencing, weather protection of exposed timber, and coordination of MEP penetrations all need to be resolved earlier, because changes after fabrication are costly. Early involvement of the fabricator and engineer is a common recommendation.
Real Examples
Common Misconceptions
People assume: Wood buildings are automatically a fire risk.
Actually: Mass timber chars at a predictable rate and retains structural capacity. Code requirements for fire resistance and protection apply, and the code sets limits by construction type.
People assume: Mass timber is the same as regular wood framing.
Actually: It is an engineered, prefabricated system with different connections, tolerances, fabrication lead times, and sequencing from stick-built light-frame construction.
Frequently Asked Questions
What products count as mass timber?
Common products are cross-laminated timber, glue-laminated timber, nail-laminated timber, dowel-laminated timber, mass plywood panels, and laminated veneer lumber, used as panels, beams, and columns.
How tall can mass timber buildings be under the IBC?
It depends on the construction type, occupancy, and adopted code edition. The 2021 IBC created Types IV-A, IV-B, and IV-C, with the highest type permitting the tallest buildings. Local amendments can change the limits.
Is mass timber more sustainable than concrete or steel?
It can have lower embodied carbon and stores biogenic carbon, but results depend on the wood source, transport, the whole building design, and the accounting method used. A life-cycle assessment gives project-specific answers.
What should contractors coordinate early?
Fabrication lead times, shop drawings, MEP penetrations, connection details, moisture protection during construction, and sequencing with the crane and delivery plan.