CA Health & Safety Code Section 19850

The building department of every city or county shall maintain an official copy, which may be on microfilm or other type of photographic copy, of the plans of every building, during the life of the building, for which the department issued a building permit. “Building department” means the department, bureau, or officer charged with the enforcement of laws or ordinances regulating the erection, construction, or alteration of buildings. Except for plans of a common interest development as defined in Section 4100 or 6534 of the Civil Code, plans need not be filed for:

(a)

Single or multiple dwellings not more than two stories and basement in height.

(b)

Garages and other structures appurtenant to buildings described under subdivision (a).

(c)

Farm or ranch buildings.

(d)

Any one-story building where the span between bearing walls does not exceed 25 feet. The exemption in this subdivision does not, however, apply to a steel frame or concrete building.