Oregon Approves Tall Timber Buildings

Oregon has become the first U.S. state to provide code approval for construction of tall-timber buildings (over six stories) via a hybrid approach. Crosslaminated timber and other mass timber products are allowed if the vertical elements of the seismic force-resisting system are concrete, steel, or masonry. It provided new classifications of “Type IV” or “heavy timber” buildings.

The new classifications are:

• Type IV A – Buildings with automatic sprinkler systems that require three-hour fire-resistance-rated primary structural frame elements and bearing walls, with two-hour fire-resistance-rated floors. Exposed timber surfaces must be entirely encapsulated. Can achieve 18 stories and 270 ft.
  high for certain occupancies.
• Type IV B – Buildings with automatic sprinkler systems that require two-hour fire resistance-rated primary structural frame elements and bearing walls, with two-hour fire-resistance-rated floors. A calculated percentage of the exposed timber surfaces may remain exposed. May achieve 12 stories
  and 180 ft. high for certain occupancies.
• Type IV C – Buildings with automatic sprinkler systems that require two-hour fire-resistance-rated primary structural frame elements and bearing walls, with two-hour fire-resistance-rated floors. Exposed timber surfaces are permitted to remain entirely exposed. May achieve nine stories and 85 ft. high for certain occupancies. In June 2017, officials in Portland, OR, approved plans for a 90,000-sq.-ft., 12-story mixed-use project that would have been ranked as one of the tallest timber high-rises in North America. That project is currently on hold.