(

a) Except as provided in subdivision (b), all plans, specifications, and estimates shall be prepared by a licensed architect holding a valid certificate under

Chapter 3 (commencing with

Section 5500) of Division of the Business and Professions Code or by a structural engineer holding a valid certificate to use the title structural engineer under

Chapter 7 (commencing with

Section 6700) of Division of the Business and Professions Code, and the observation of the work of construction shall be under the responsible charge of such an architect or structural engineer. (

b) For the purposes of this section, a mechanical or electrical engineer holding a valid certificate under

Chapter 7 (commencing with

Section 6700) of Division of the Business and Professions Code may be in responsible charge of preparation of plans, specifications, and estimates, and observation of the work of construction where the work is, as determined by the Department of General Services, of the kind normally performed by engineers certified in the particular branch of engineering for which the engineer is certified. Any architectural or structural work involved shall be the respective responsibility of a licensed architect holding a valid certificate under

Chapter 3 (commencing with

Section 5500) of Division of the Business and Professions Code, or a structural engineer holding a valid certificate to use the title structural engineer under

Chapter 7 (commencing with

Section 6700) of Division of the Business and Professions Code.