California Code, Business and Professions Code - BPC § 7058

(a) A specialty contractor is a contractor whose operations involve the performance of construction work requiring special skill and whose principal contracting business involves the use of specialized building trades or crafts.

(b) A specialty contractor includes a contractor whose operations include the business of servicing or testing fire extinguishing systems.

(c) A specialty contractor includes a contractor whose operations are concerned with the installation and laying of carpets, linoleum, and resilient floor covering.

(d) A specialty contractor includes a contractor whose operations are concerned with preparing or removing roadway construction zones, lane closures, flagging, or traffic diversions on roadways, including, but not limited to, public streets, highways, or any public conveyance.