What is the absolute tallest light-frame wood podium allowed by IBC?

The maximum height is limited by the 85 ft total height limit for Type IIIa construction.  This is found in Table 504.3.

Table 504.4 says that a Type IIIa (this is light-frame wood construction with special fire ratings) building can be 5 stories maximum for a Residential use.

So……there is a scenario where we can put 5-stories for light framed wood on a 3-story podium (steel or concrete) and keep it under the 85 ft.  See the diagram above.

What are the compromises?

To build the 8-story building depicted in the diagram above, there is typically a compromise in floor-floor height to squeeze below the limit.

Strategies to make this work?

  1. Grade can be your friend – the max building height is measured from average grade, so if you have a sloping site, average grade can be above the ground floor elevation.
  2. Use post-tensioned concrete for the podium levels.  PT provides the thinnest structural system to help maximize ceiling height.
  3. Consider not using sloped roof trusses.  This can help gain ~12″ from the roof structure assembly.

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