Significant changes to concealed spaces in Type IV-HT of the 2021 International Building Code
The 2021 Significant Changes guides are available for the International Building, Residential, Fire, Energy Conservation, Plumbing, Mechanical and Fuel Gas Codes. This valuable series can help any code user save time by zeroing in on the most critical changes in the 2021 International Codes. The Code Council’s technical experts provide summaries, analysis and graphics for these changes making them clear and easy to understand.
2021 International Building Code
A modification to Section 2304.11 (Concealed Spaces in Type IV-HT) states that concealed spaces are now permitted in floors and roof decks for Type IV-HT.
Historically, concealed spaces have not been permitted in traditional heavy timber construction. Now, concealed spaces are permitted in traditional Type IV-HT construction, with specific requirements for their protection. New protection options include:
- In fully sprinklered buildings, installing automatic sprinkler protection in the concealed space.
- Filling the space with noncombustible insulation.
- Protecting combustible surfaces with not less than 5/8-inch Type X gypsum board.
Concealed spaces in new Types IV-A, IV-B and IV-C construction are addressed separately. The option of having protected concealed spaces in Type IV-HT buildings is important for encouraging adaptive re-use of existing heavy timber buildings as well as providing for the installation of mechanicals (MEP) in Type IV-HT cross-laminated timber construction.
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