Special Inspections of Mass Timber Construction

The International Building Code (IBC), 2021 Edition, Chapter 17, adds a new Table 1705.5.3 listing the required special inspections of mass timber construction. The table lists several code-required special inspections related to mass timber construction. IBC defines mass timber construction as “structural elements of Type IV construction primarily of solid, built-up, panelized or engineered wood products that meet minimum cross-section dimensions of Type IV construction.”

The thermal protection of exposed mass timber elements used as occupancy separations or incidental use separations only applies to buildings classified as Type IV-B or IV-C construction. There is no need to regulate Type IV-A due to the mandatory noncombustible protection of all mass timber elements.

It is important to note that the thermal barrier requirements are only established to address the possible contribution of exposed mass timber surfaces to the fuel load.

IBC Section 509.4.1.1 Type IV-B and IV-C Construction

Where Table 509.1 specifies a fire-resistance-rated separation, mass timber elements serving as fire barriers or horizontal assemblies in Type IV-B or IV-C construction shall be separated from the interior of the incidental use with an approved thermal barrier consisting of gypsum board that is not less than ? inch in thickness or a material that is tested in accordance with and meets the acceptance criteria of both the Temperature Transmission Fire Test and the Integrity Fire Test of National Fire Protection Association (NFPA) 275.

For more information or further enthusiastic discourse on topics of CODE, please contact Alan Tuck at: [email protected] or 540.344.7939