This scenario was used for Clay Creative, also in Portland (pictured below). ![]() This typically results in the use of 5-ply CLT or 2×6 NLT floor panels, spanning 14 or 15 ft. Larger square grids such as 28×28 or 30×30 ft with one intermediate beam can also be used. This scenario was used for the Albina Yard office building in Portland, OR (pictured above). For example, a 20×20-ft grid could have one intermediate beam so 3-ply CLT floor panels spanning 10 ft can be used. Although a mass timber panel may be able to span the 20-ft distance between support beams in a 20×20-ft grid, an alternate method would be to include one intermediate beam within each bay to reduce the span of the mass timber floor panel. Design and Construction Guide.īased on completed buildings in the US, square grids tend to be in the range of 20×20 to 30×30 ft. (Each project’s specific span, loading and support conditions, as well as manufacturer-specific design properties, should be accounted for when selecting panel thickness.) For more details on the structural design of mass timber floor panels, contact your local WoodWorks Regional Director or email the WoodWorks help desk at For additional information, see the Structure magazine article, Cross-Laminated Timber Structural Floor and Roof Design, and Nail-Laminated Timber: U.S. ![]() The table below illustrates example ranges based on panel size, assuming stiff supports. In addition to panel vibration design, vibration performance of the framing system as a whole, including beams, should be taken into account. Due to their relative light weight, allowable spans for these panels are often governed by vibration and deflection rather than bending or shear capacity. To determine efficient grid spacing, it is important to understand possible span ranges for mass timber floor panels. In deciding which to use, there are a number of factors to consider. Simplistically, there are two main grid options for mass timber buildings: square and rectangular. The following considerations are based on a post-and-beam frame for occupancies such as offices however, many also apply to bearing wall-supported systems in other occupancy types. This requires a thorough understanding of how to best lay out the structural grid, without sacrificing space functionality, to optimize member sizes-but there’s more to cost efficiency than column spacing. As such, it is critically important to design a mass timber building as a mass timber building from the start. Trying to force a mass timber solution on a grid laid out for steel and concrete can result in member size inefficiencies while negating opportunities related to manufacturer capabilities. Although a mass timber solution may work economically on many grids conducive to steel/concrete framing, some grid modification may be valuable. When it comes to laying out a structural grid for mass timber, the square peg/round hole analogy is pertinent. Intended to meet the need for tenant flexibility, these “default” grids align with the capabilities of materials historically used-i.e., steel and concrete. Mass timber is commonly seen in projects such as offices, schools and tall mixed-use buildings, which often have assumed structural grids. This requires a full understanding of both material properties and manufacturer capabilities. However, to convince building owners and developers that a mass timber solution is viable, the structural design must also be cost competitive. In addition to its sustainability and light carbon footprint, mass timber has benefits that include enhanced aesthetics, speed of construction and light weight, all of which can positively impact costs. ![]() At no time has materials selection been such an integral aspect of the building designer’s daily responsibilities. Mass timber products such as cross-laminated timber (CLT), nail-laminated timber (NLT) and glue-laminated timber (glulam) are at the core of a revolution that is shifting how designers think about construction.
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