The provisions of this chapter do not apply to any person licensed as a general contractor under the provisions of Chapter 11 of Title 40 for the purpose of undertaking the construction, or superintending of construction, of any building, or the improvement, reimprovement, or repair of any building. No residential builder who is licensed pursuant to the provisions of this chapter is also required to be licensed as a general contractor or mechanical contractor under the provisions of Chapter 11 of Title 40 in order to engage in residential building as defined in Section 40-59-10. A mechanical contractor is exempt from the provisions of this chapter relating to residential specialty contractors when engaged in contracting in the classification in which he is licensed to perform mechanical contracting. The Residential Builders Commission is the sole licensing and registration board for persons who engage solely in residential building as defined in Section 40-59-10 and in residential specialty contracting as defined in Section 40-59-15.