Tallest US Mass-Timber Tower to Rise in Oakland

Oakland-based developer oWow has again increased the size of the mass-timber apartment tower it is planning to build at 1523 Harrison Street, next to a 19-story mass-timber building oWow put up in downtown Oakland last year.

The project now will have 28 stories encompassing 496 units, up from the original plan for a 20-story twin of the neighboring building, the San Francisco Business Times reported.

If the new plan is completed, oWow’s tower will be the tallest mass-timber building in the U.S.

That title currently belongs to the Ascent MKE Building, a 25-story structure that opened in Milwaukee in 2022. The U.S. Forest Service supported the Ascent project with a wood products innovation grant for design and engineering.

OWow achieved a 76% density bonus under local and state law by adding 214 units to its Harrison Street project. Half of the bonus comes from Oakland; a 26% density bonus came from AB 1278, a new state law that lets developers stack numerous density bonuses in exchange for reserving 15% of the tower’s units for middle-income households.

“This increase in density provides significant cost-savings that are critical for making the project economically viable in a difficult market for Oakland,” oWow’s application said.

Mass timber is gaining favor as developers seek to reduce the carbon footprint of their buildings by reducing the amount of concrete, which generates significant emissions when it is made. As a construction material, pre-fabricated mass-timber components can be assembled much faster than concrete and steel structures.

OWow paid $9.3M in March 2022 for a half-acre site next to a 19-story, 236-unit mass-timber apartment building oWow completed last year at 1510 Webster Street. Power-related delays have prevented the Webster Street building from opening.

In 2021, California updated its building code to allow mass-timber buildings to reach 18 stories, after the International Building Code approved high-rise mass-timber structures.

The Golden State also increased the square footage allowed on mass-timber buildings and issued guidelines for architects. Prior to the change, mass-timber buildings had been capped at six stories for residential buildings due to safety concerns.

oWow, which already had a project underway at the Harrison Street site when the building code update was issued, immediately revised its plans to convert the design to a mass-timber high-rise built atop a single story of concrete, with a cutout halfway up for a landscaped patio deck.

Before the IBC approved high-rise mass-timber buildings, the U.S. Forest Service’s products lab conducted critical fire testing of glued-laminated timber columns, also known as Glulam, a manufactured construction product composed of layers of lumber glued together.

According to the Forest Service, the three-hour burn test proved that oversized, yet unprotected, glulam columns do not lose structural integrity because outer layer charring protects internal layers of the wooden building components.