The exterior is granite from the nearby Raymond quarries,[further explanation needed] chosen for its hardness and uniform color.

[4] The roof is concrete-sheathed steel covered in Spanish mission tiles (tejas), reflecting Howard's desire to create a uniquely "Californian" architectural style.

Similar to the Hearst Memorial Mining Building being built on the university campus by Howard at the same time, the interior was made to be architecturally "elastic"—these same subdivisions could be cheaply and easily removed without compromising the structure's exterior steel shell.

[4] The main entrance on the west side of the building opened to a first-floor lobby that had marble paneling in a wainscot fashion.

The room was intended for the university's large History, English and Botany classes, which were difficult to accommodate previously due to a lack of adequate indoor space on the campus.

To the south of the large lecture hall were classrooms and faculty offices, uniformly painted ivory in color.

[4] On the top floor of the building were the headquarters of the University Press and Editorial Committee, and the Botanical Museum (herbarium), which was brought there to protect it from fire.

[3] The attic was fitted with steel bookshelves in 1906, becoming the first on-campus location of the recently acquired Bancroft Library, which had previously been housed in San Francisco.

This system drew in outside air, filtering it through a fine cloth mesh to remove dust, and was warmed after being passed across the surface of steam coils.

A large revolving fan pushed the heated air through the ventilation system, with units installed in each of the rooms throughout the entire building.

Howard said of California Hall that it was a: free study of modified classic forms without recourse to ... columnar orders.