ICC code changes to allow CLT construction up to 18 storeys

4 January 2019

The International Code Council (ICC) has approved an entire package of 14 tall mass timber code change proposals which will see some CLT buildings allowed up to 18 storeys.

The ICC’s unofficial voting results on code change proposals, expected to be officially announced during the first quarter of 2019, include creating three new types of construction (Types IV-A, IV-B and IV-C), which set fire safety requirements, and allowable heights, areas and number of stories for tall mass timber buildings.

The new provisions will be included in the 2021 International Building Code (IBC). “Mass timber has been capturing the imagination of architects and developers, and the ICC result means they can now turn sketches into reality,” said American Wood Council (AWC) president & CEO Robert Glowinski.

“ICC’s rigorous study, testing and voting process now recognizes a strong, low-carbon alternative to traditional tall building materials used by the building and construction industry.”

The three new types of construction that will be included in the 2021 IBC are:

• Type IV-A – Maximum 18 stories, with gypsum wallboard on all mass timber elements.

• Type IV-B – Maximum 12 stories, limited-area of exposed mass timber walls and ceilings allowed.

• Type IV-C – Maximum 9 stories, all exposed mass timber designed for a 2-hour fire resistance.

“The addition of tall mass timber to the International Building Code provides a comprehensive set of safety standards for these new types of construction,” added AWC Vice President of Codes & Regulations Kenneth Bland.

“This vote caps off several years of scientific research and testing, and verifies that mass timber meets the robust performance standards called for by our nation’s building codes.”

ICC’s code development cycle continues through 2019. Additional structural requirements for tall mass timber buildings will be considered, with final approval of 2019 proposals expected to occur in late October.

ICC codes are recognised across the US and are also active in about 55 countries.

The 2021 IBC is expected to be released in late 2020, along with the full set of 2021 I-codes. Meanwhile, Structurlam cross-laminated timber (CLT) is the first CLT system to be officially listed as complying with existing building codes and standards in North America.

Issued by the International Code Council Evaluation Services (ICC-ES) and APA –The Engineered Wood Association - the joint evaluation report is the first issued under a new product listing programme for manufacturers of CLT products.

ICC has approved higher rise CLT structures