Bio-based materials are a promising way to store carbon in buildings, as agricultural materials pull carbon out of the air on an annual basis. Some bio-based materials have gained a following, but are generally confined to single-family or low-rise, specialty projects. If we are to reach a net zero carbon built environment by 2050, including embodied carbon, we must find a way to scale up the use of these materials. With this case study we offer the San Francisco Bay Area and wider community a prototype to demonstrate – using the BEAM Calculator Tool – how carbon-storing (i.e. bio-based) materials can be scaled to larger residential buildings, California's most desperately needed building type. Included are examples in several other developed countries where they have scaled to bio-based materials to larger, taller construction.