Tallest Mass Timber Tower on West Coast Gets Twin

An Oakland-based developer who already has under construction a 19-story, 236-unit residential tower in Oakland what will become the tallest mass timber building on the West Coast when completed has decided to double the size of the project.

Oakland-based developer oWow is planning to build a second 19-story mass timber tower, this one with 269 units, on a half-acre lot at 1523 Harrison Street that oWow purchases for $9.3M in March, according to a report in the San Francisco Business Times.

The company said the second tower will have the same design as the building under construction at 1510 Webster Street: 18 stories of mass timber atop a single story of concrete. The buildings will each have a cutout halfway up for a landscaped patio deck, and each will have about 15K of retail and office space.

Last summer, 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 after conducting a series of fire safety tests.

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 last summer, immediately revised its plans to convert the design to a mass timber high rise.

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 told the Business Times it is aiming to put up the mass timber high-rise apartment buildings at a pace of two floors a week. The developer previously built a five-story mass timber building at 316 12^th Street in Oakland at a rate of one story per week.

The Harrison and Webster mass timber towers will both feature one- and two-bedroom apartments from 400K SF to 700K SF. The developer says the units will be “affordable by design,” with floor plans that reduce foyers and hallways.

The tallest mass timber building in the world right now is the Ascent MKE Building, a 25-story structure that opened in Milwaukee this year. The US Department of Agriculture’s Forest Service supported the project with a wood products innovation grant for design and engineering.

The 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.