Some tiny house builders follow particular building codes to be certified in order to meet minimum requirements of a standard house. Not all tiny house builders may follow these codes. Inquire with your builder as to what codes are followed for your tiny house.
Taken from this page:
The Recreation Vehicle Industry Association (RVIA) is the national trade association representing recreation vehicle (RV) manufacturers and their component parts suppliers who together build more than 98 percent of all RVs produced in the U.S.
Their standards are located here.