Located in Marin County, the CMU house derives it name from the acronym for the Concrete Masonry Unit, also known as concrete block. Unique to a residence of this scale, all exterior and interior walls of the original house were constructed entirely with CMU blocks. This project creates a new room addition to the house, as well as complete exterior and interior renovations. Sited at the base of a steep mountain incline with redwood trees, the design concept transforms the existing building into a light and porous architecture that dramatically opens to the horizontal and vertical views outward.