The International Code Council (ICC) has approved 17 changes to the 2021 editions of the International Building Code (IBC) and International Fire Code, allowing for mass timber buildings up to 18 stories. With the addition of three new mass timber construction types (Type IV-A, IV-B, and IV-C), this is the first time in the history of the modern building code that significantly new construction types have been added to the code.
The primary building material that makes tall mass timber (TMT) buildings possible is cross-laminated timber (CLT). CLT is manufactured from dimension lumber (nominal 2x lumber) laid side-by-side or mass plywood panels of a specified width. Laminations of lumber are typically laid perpendicular to each other to form panels of various thicknesses that are bonded together using heat resistant adhesives that cure in large hydraulic presses. CLT commonly consists of an odd number of laminations.
These solid wood panels can be anywhere from 6 inches to 20 inches nominal thickness and 60 feet long. Typical CLT panels will be 6 inches to 14 inches nominal thickness. The panels are fabricated off site, transported onto the construction site and assembled in a manner that is efficient and remarkably fast. CLT panels can be used as floor, wall, or roof building elements supported by glued-laminated beams and columns.
Reprinted courtesy of Kenneth Bland, Construction Executive, a publication of Associated Builders and Contractors. All rights reserved.